Lignin metabolism has a central role in the resistance of cotton to the wilt fungus Verticillium dahliae as revealed by RNA-Seq-dependent transcriptional analysis and histochemistry

The ZjMYB44-ZjPOD51 module enhances jujube defense response against phytoplasma by upregulating lignin biosynthesis

Lignin is a major component of the plant cell wall and has a conserved basic defense function in higher plants, helping the plants cope with pathogen infection. However, the regulatory mechanism of lignin biosynthesis in plants under phytoplasma stress remains unclear. In this study, we reported that peroxidase 51 (ZjPOD51), which is involved in lignin monomer polymerization, was induced by phytoplasma infection and that overexpression of ZjPOD51 in phytoplasma-infected jujube seedlings and Arabidopsis plants significantly increased their defense response against phytoplasma. Yeast one-hybrid (Y1H) and luciferase (LUC) assays showed that ZjPOD51 transcription was directly upregulated by ZjMYB44. Genetic validation demonstrated that ZjMYB44 expression was also induced by phytoplasma infection and contributed to lignin accumulation, which consequently enhanced phytoplasma defense in a ZjPOD51-dependent manner. These results demonstrated that the ZjMYB44-ZjPOD51 module enhanced the jujube defense response against phytoplasma by upregulating lignin biosynthesis. Overall, our study first elucidates how plants regulate lignin to enhance their defense response against phytoplasma and provides clues for jujube resistance breeding.

Casein kinase GhCKA1 positively regulates cotton resistance to Verticillium wilt

Verticillium wilt is an important disease that seriously affects the quality and yield of cotton. Fungal vascular diseases caused by Verticillium dahliae hinders the sustainable development of cotton cultivation. The most effective strategy for managing Verticillium wilt in cotton involves identifying resistance genes, investigating resistance mechanisms, and developing resistant varieties. In the laboratory, in our previous work, V. dahliae strain Vd080 was inoculated into both disease-resistant and disease-susceptible cotton strains, followed by a comprehensive transcriptomic analysis. The findings confirms the correlation between the gene GhCKA1 and disease resistance. In this study, silencing GhCKA1 expression led to reduced levels of reactive oxygen species, callose, and xylem accumulation, thereby inhibiting various defense responses and reducing cotton resistance to V. dahliae. Furthermore, we observed increased resistance to pathogens in Arabidopsis thaliana overexpressing GhCKA1. Subcellular localization experiments in tobacco indicated that GhCKA1 is localized within the nucleus. GUS staining analysis showed that the expression of the GhCKA1 promoter was influenced by pathogenic microorganisms. Additionally, we found that GhCKA1 interacts with aspartic proteases, an important proteolytic enzymes that play significant roles in metabolism and biological regulation. In conclusion, GhCKA1 enhances the resistance of cotton to V. dahliae and interacted with GhAsp1. Therefore, GhCKA1 may be a suitable molecular target to improve the resistance of cotton to Verticillium wilt, and provide a new breeding method for cotton to resist Verticillium wilt.

Verticillium dahliae effector Vd06254 disrupts cotton defence response by interfering with GhMYC3-GhCCD8-mediated hormonal crosstalk between jasmonic acid and strigolactones

Verticillium dahliae is among the most destructive plant pathogens, posing a significant threat to global cotton production. Cotton plants have developed sophisticated immune networks to inhibit V. dahliae colonization. Ingeniously, V. dahliae employs numerous virulent effectors to surmount plant immune responses. However, the pathogenic mechanisms of V. dahliae-derived effectors remain elusive. In this study, we demonstrate that the Vd06254 effector from V. dahliae disrupts the synergistic interaction between jasmonic acid (JA) and strigolactones (SL), thereby suppressing cotton immunity. Ectopic expression of Vd06254 enhanced susceptibility to both viral and V. dahliae infections in Nicotiana benthamiana and cotton, respectively. Vd06254 directly interacts with the JA pathway regulator GhMYC3. The nuclear localization signal (NLS) was found to be essential for the virulence of Vd06254 and its interaction with GhMYC3. Additionally, overexpression and knockout of GhMYC3 in cotton modified the plant's resistance to V. dahliae. Our findings further reveal that GhMYC3 inhibits the expression of GhCCD8 by binding to its promoter, potentially regulating SL homeostasis in cotton through a negative feedback loop. This repression was enhanced by Vd06254, highlighting its crucial role in modulating cotton immunity and illustrating how V. dahliae effectors reprogram cotton transcription to disrupt this regulatory mechanism.

Integrated metabolome and transcriptome analysis of maize roots response to different degrees of drought stress

BACKGROUND

Plants in arid environments can regulate the generation of specialized metabolites to enhance their adaptability. Roots serve as the first defense line, responding directly to drought situations; however, the knowledge regarding the molecular mechanisms of metabolite changes to drought in maize roots remain largely limited. Here, we employed RNA-seq and UPLC-MS/MS methods to examine changes in the root metabolome and transcriptome of maize seedlings subjected to moderate drought (MD) and severe drought (SD) conditions by controlling water supply.

RESULTS

Compared to the untreated control group, 460 differentially accumulated metabolites were detected in roots under MD and SD conditions. Among these metabolites, lignin compounds emerged as the primary response to drought. Most lignin metabolites, including caffealdehyde, sinapyl alcohol, coniferaldehyde, p-coumaryl alcohol, and p-coumaric acid, showed a significant increase under MD but decreased under SD. Transcriptional profiling identified 903 and 5306 differential genes in roots treated with MD and SD, respectively. The majority of these genes were associated with lignin biosynthesis, hormone synthesis and signal transduction, and defense response processes. These metabolites and genes play crucial roles in lignin biosynthesis, antioxidant capacity, hormone balance, and root growth, particularly under MD conditions, which aligns with the results from morpho-physiological studies. Further, a conjoint omics analysis highlighted the significant regulatory roles of hormone-associated genes in lignin formation.

CONCLUSION

Our results suggest that the co-regulation of the lignin biosynthesis pathway and hormone signals significantly enhances root performance, helping maize maintain growth under MD conditions. This study leads to a better understanding of the regulatory mechanisms involved in maize root adaptation to drought environments.

The Magnaporthe oryzae effector MoBys1 suppresses rice immunity by targeting OsCAD2 to manipulate host jasmonate and lignin metabolism

Rice blast disease caused by Magnaporthe oryzae poses a severe threat to rice production. To counteract M. oryzae, plants synthesize jasmonate (JA) and lignin, two primary defense-related metabolites, to initiate defense programs. However, the mechanism through which M. oryzae modulates JA- and lignin-mediated plant immunity remains unclear. In this study, a novel M. oryzae effector, MoBys1, was identified as being involved in pathogenesis. Knockout of MoBys1 in M. oryzae significantly reduced its infection ability. Conversely, overexpression of MoBys1 in rice impaired the rice defense response. MoBys1 localizes to the plant cytoplasm and nucleus and interacts with rice cinnamyl alcohol dehydrogenase 2 (OsCAD2), an enzyme that catalyzes lignin biosynthesis. While OsCAD2 mutants exhibited weakened defenses, overexpression lines demonstrated enhanced resistance, highlighting the critical role of OsCAD2 in blast resistance. Furthermore, OsCAD2 functions as a transcription factor regulating a wide range of biological processes, including JA and lignin signaling pathways. The interaction between MoBys1 and OsCAD2 promotes OsCAD2 degradation, leading to reduced lignin and JA accumulation. These findings uncover a novel counter-defense mechanism by which M. oryzae employs the effector MoBys1 to degrade OsCAD2 and suppress host defense-related metabolite accumulation during infection.

CRISPR/dCas12a-mediated activation of SlPAL2 enhances tomato resistance against bacterial canker disease

Crop protection is essential for maintaining and improving agricultural productivity. While pesticides are commonly used to control pests, they pose several challenges, including environmental harm and health risks. Alternative strategies to pesticides include breeding resistant crop varieties, biological control, and utilizing genome-editing tools like CRISPR/Cas. However, the application of epigenome editing, particularly CRISPR activation (CRISPRa), in plants remains underexplored. Phenylalanine ammonia-lyase (PAL), a key enzyme in the phenylpropanoid pathway, plays a pivotal role in plant defense by producing lignin and other secondary metabolites essential for pathogen resistance. In this study, we engineered tomato plants by fusing the SET-domain of the SlATX1 coding gene, a histone H3 lysine 4 tri-methyltransferase, to dCas12a, targeting the SlPAL2 promoter with the aim to increase PAL2 gene expression. CRISPRa-edited plants demonstrated increased deposition of the H3K4me3 epigenetic mark and significantly upregulated SlPAL2 expression. This enhanced lignin accumulation and conferred increased resistance to Clavibacter michiganensis subsp. michiganensis (Cmm) without significant reduction in plant height or fruit yield. Disease resistance was also associated with reduced pathogen load and lesion size, and higher lignin levels persisted even after SlPAL2 expression declined post-infection. These findings highlight the potential of CRISPRa for reprogramming plant defense responses through targeted histone modifications, offering a sustainable approach for crop improvement. Furthermore, CRISPRa could also be applied to enhance crop resilience in other contexts, such as addressing food security challenges by enhancing productivity.

Transcriptome analysis of wild olive (Olea Europaea L. subsp. europaea var. sylvestris) clone AC18 provides insight into the role of lignin as a constitutive defense mechanism underlying resistance to Verticillium wilt

Host resistance is the most effective and practical control method for the management of Verticillium wilt in olive caused by Verticillium dahliae, which remains as one of the major current threats to this crop. Regrettably, most olive cultivars of agronomic and commercial interest are susceptible to V. dahliae. We previously demonstrated that wild olive (Olea europaea L. subsp. europaea var. sylvestris) clone AC18 harbours resistance to the highly virulent defoliating (D) V. dahliae pathotype, which may be valuable as rootstock and for breeding new, resistant olive cultivars. Mechanisms underlying disease resistance may be of constitutive or induced nature. In this work we aim to unravel constitutive defences that may be involved in AC18 resistance, by comparing the transcriptome from uninfected stems, of AC18 with that of the highly susceptible wild olive clone AC15, GO-term enrichment analysis revealed terms related to systemic acquired resistance, plant cell wall biogenesis and assembly, and phenylpropanoid and lignin metabolism. qRT-PCR analysis of phenylpropanoid and lignin metabolism-related genes showed differences in their expression between the two wild olive clones. Phenolic content of stem cell walls was higher in the resistant AC18. The total lignin content was similar in resistant and susceptible clones, but they differed in monolignol composition. Results from this work identifies putative key genes in wild olive that could aid in breeding olive cultivars resistant, to D. V. dahliae. The research highlights the constitutive defence mechanisms that are effective in protecting against pathogens and our findings may contribute to the deciphering the molecular basis of VW resistance in olive and the conservation and utilization of wild olive genetic resources to tackle future agricultural challenges towards.

LACCASE35 enhances lignification and resistance against Pseudomonas syringae pv. actinidiae infection in kiwifruit

Kiwifruit bacterial canker, a highly destructive disease caused by Pseudomonas syringae pv. actinidiae (Psa), seriously affects kiwifruit (Actinidia spp.) production. Lignin deposition in infected cells serves as a defense mechanism, effectively suppressing pathogen growth. However, the underlying process remains unclear. In this study, we determined that Psa infection leads to a significant increase in S-lignin accumulation in kiwifruit. The S/G ratio in lignin was higher in a Psa-resistant cultivar than in a Psa-sensitive cultivar. Furthermore, kiwifruit laccase 35 (AcLac35), encoding an enzyme in the lignin biosynthesis pathway with characteristic laccase activity, showed tissue-specific expression in plants and was upregulated following infection by Psa. Overexpressing AcLac35 in kiwifruit leaves resulted in greater lignin content than in wild-type leaves, leading to the formation of thicker cell walls, and also activated plant-pathogen interactions and MAPK pathways, thereby enhancing resistance against Psa infection. Yeast 1-hybrid assays, dual-LUC reporter assays, electrophoretic mobility shift assays, and transient injection experiments indicated that SQUAMOSA PROMOTER-BINDING PROTEIN-LIKE 9 (AcSPL9) can bind to the AcLac35 promoter, thereby positively regulating its expression. Moreover, overexpression of AcSPL9 increased lignin accumulation in kiwifruit leaves, enhancing resistance to Psa, while virus-induced gene silencing of AcSPL9 expression reduced this resistance. Our findings reveal the function of AsSPL9-AcLac35 in kiwifruit, providing insight into enhancing resistance against Psa in kiwifruit.

Integrated Transcriptomic and Metabolomic Analysis of G. hirsutum and G. barbadense Responses to Verticillium Wilt Infection

Verticillium wilt (VW) caused by Verticillium dahliae (Vd) is a devastating fungal cotton disease characterized by high pathogenicity, widespread distribution, and frequent variation. It leads to significant losses in both the yield and quality of cotton. Identifying key non-synonymous single nucleotide polymorphism (SNP) markers and crucial genes associated with VW resistance in Gossypium hirsutum and Gossypium barbadense, and subsequently breeding new disease-resistant varieties, are essential for VW management. Here, we sequenced the transcriptome and metabolome of roots of TM-1 (G. hirsutum) and Hai7124 (G. barbadense) after 0, 1, and 2 days of V991 inoculation. Transcriptome analysis identified a total of 72,752 genes, with 5814 differentially expressed genes (DEGs) determined through multiple group comparisons. KEGG enrichment analysis revealed that the key pathways enriched by DEGs obtained from both longitudinal and transverse comparisons contained the glutathione metabolism pathway. Metabolome analysis identified 995 metabolites, and 22 differentially accumulated metabolites (DAMs), which were correlated to pathways including glutathione metabolism, degradation of valine, leucine, and isoleucine, and biosynthesis of terpenoids, alkaloids, pyridine, and piperidine. The conjoint analysis of transcriptomic and metabolomic sequencing revealed DAMs and DEGs associated with the glutathione metabolism pathway, and the key candidate gene GH_D11G2329 (glutathione S-transferase, GSTF8) potentially associated with cotton response to VW infection was selected. These findings establish a basis for investigating the mechanisms underlying the cotton plant's resistance to VW.

Histone deacetylase GhHDA5 negatively regulates Verticillium wilt resistance in cotton

Verticillium wilt (VW) caused by Verticillium dahliae (V. dahliae) is one of the most destructive diseases in cotton (Gossypium spp.). Histone acetylation plays critical roles in plant development and adaptive responses to biotic and abiotic stresses. However, the relevance of histone acetylation in cotton VW resistance remains largely unclear. Here, we identified histone deacetylase 5 (GhHDA5) from upland cotton (Gossypium hirsutum L.), as a negative regulator of VW resistance. GhHDA5 expression was responsive to V. dahliae infection. Silencing GhHDA5 in upland cotton led to improved resistance to V. dahliae, while heterologous expression of GhHDA5 in Arabidopsis (Arabidopsis thaliana) compromised V. dahliae tolerance. GhHDA5 repressed the expression of several lignin biosynthesis-related genes, such as 4-coumarate:CoA ligase gene Gh4CL3 and ferulate 5-hydroxylase gene GhF5H, through reducing the acetylation level of histone H3 lysine 9 and 14 (H3K9K14ac) at their promoter regions, thereby resulting in an increased deposition of lignin, especially S monomers, in the GhHDA5-silenced cotton plants. The silencing of GhF5H impaired cotton VW tolerance. Additionally, the silencing of GhHDA5 also promoted the production of reactive oxygen species (ROS), elevated the expression of several pathogenesis-related genes (PRs), and altered the content and signaling of the phytohormones salicylic acid (SA), jasmonic acid (JA), and strigolactones (SLs) after V. dahliae infection. Taken together, our findings suggest that GhHDA5 negatively regulates cotton VW resistance through modulating disease-induced lignification and the ROS- and phytohormone-mediated defense response.

Natural SNP Variation in GbOSM1 Promotor Enhances Verticillium Wilt Resistance in Cotton

Osmotin is classified as the pathogenesis-related protein 5 group. However, its molecular mechanism involved in plant disease resistance remains largely unknown. Here, a Verticillium wilt (VW) resistance-related osmotin gene is identified in Gossypium barbadense (Gb), GbOSM1. GbOSM1 is preferentially expressed in the roots of disease-resistant G. barbadense acc. Hai7124 and highly induced by Verticillium dahliae (Vd). Silencing GbOSM1 reduces the VW resistance of Hai7124, while overexpression of GbOSM1 in disease-susceptible G. hirsutum improves tolerance. GbOSM1 predominantly localizes in tonoplasts, while it relocates to the apoplast upon exposure to osmotic stress or Vd infection. GbOSM1 confers VW resistance by hydrolyzing cell wall polysaccharides of Vd and activating plant immune pathways. Natural variation contributes to a differential CCAAT/CCGAT elements in the OSM1 promoter in cotton accessions. All G. hirsutum (Gh) exhibit the CCAAT haplotype, while there are two haplotypes of CCAAT/CCGAT in G. barbadense, with higher expression and stronger VW resistance in CCGAT haplotype. A NFYA5 transcription factor binds to the CCAAT element of GhOSM1 promoter and inhibits its transcription. Silencing GhNFYA5 results in higher GhOSM1 expression and enhances VW resistance. These results broaden the insights into the functional mechanisms of osmotin and provide an effective strategy to breed VW-resistant cotton.

Rhamnolipid-Enriched PA3 Fraction from Pseudomonas aeruginosa SWUC02 Primes Chili Plant Defense Against Anthracnose

Chili anthracnose, caused by Colletotrichum truncatum, causes significant yield loss in chili production. In this study, we investigated the elicitor properties of a rhamnolipid (RL)-enriched PA3 fraction derived from Pseudomonas aeruginosa SWUC02 in inducing systemic resistance in yellow chili seedlings and antifungal activity against C. truncatum CFPL01 (Col). Fractionation of the ethyl acetate extract yielded 12 fractions, with PA3 demonstrating the most effective disease suppression, reducing the disease severity index to 4 ± 7.35% at 7 days post-inoculation compared with Col inoculation alone (83 ± 23.57%). PA3 also exhibited direct antifungal activity, inhibiting Col mycelial growth by 41 ± 0.96% at 200 µg/mL. Subfractionation revealed PA3 as a mixture of mono- and di-RLs, confirmed by 1H nuclear magnetic resonance and electrospray ionization mass spectrometry data. Additionally, PA3 enhanced seed germination and promoted plant growth without causing phytotoxicity. Transcriptomics revealed that PA3 pre-treatment prior to Col infection primed the defense response, upregulating defense-related genes involved in the phenylpropanoid, flavonoid, and jasmonic acid biosynthesis pathways, as well as those associated with cell wall reinforcement. Our findings highlight the potential of RL-enriched PA3 as both an antifungal agent and a plant defense elicitor, with transcriptome data providing new insights into defense priming and resistance pathways in chili, offering an eco-friendly solution for sustainable anthracnose management.

A GhLac1-centered transcriptional regulatory cascade mediates cotton resistance to Verticillium dahliae through the lignin biosynthesis pathway

The lignin biosynthesis pathway plays a crucial role in the defense response against V. dahliae in cotton, and it is essential to identify the key regulators in this pathway for disease-resistant breeding. In a previous study, the cotton laccase gene GhLac1 was identified as mediating plant broad-spectrum biotic stress tolerance by manipulating phenylpropanoid metabolism. However, the upstream master regulators and regulatory mechanism of lignin are still largely unknown. This study aims to identify the upstream regulators of GhLac1 and explore the molecular mechanism underlying cotton's disease resistance response to V. dahliae. Through the study, three WRKY, three MYB, and one APETALA2/ETHYLENE RESPONSIVE FACTOR (ERF) TFs were identified as differentially responding to V. dahliae infection in cotton. Among these TFs, GhWRKY30, GhWRKY41, GhMYB42, and GhTINY2 were found to directly bind to the GhLac1 promoter and activate its expression. Transient overexpression of these four TFs in cotton led to increased expression of GhLac1 and other the laccase family members, while knockdown of these TFs resulted in reduced lignin accumulation and increased susceptibility to V. dahliae. Additionally, GhWRKY30 and GhWRKY41 were observed to interact with themselves and with each other, synergistically transactivating the GhLac1 promoter. This study reveals a GhLac1-centered transcriptional regulatory cascade of lignin synthesis that contributes to cotton's defense response by modulating lignin metabolism.

Verticillium dahliae Elicitor VdSP8 Enhances Disease Resistance Through Increasing Lignin Biosynthesis in Cotton

Verticillium wilt caused by the soil-borne fungus Verticillium dahliae Kleb., is a destructive plant disease that instigates severe losses in many crops. Improving plant resistance to Verticillium wilt has been a challenge in most crops. In this study, a V. dahliae secreted protein VdSP8 was identified and shown to activate hyper-sensitive response (HR) and systemic acquired resistance (SAR) to Pseudomonas syringae pv. tomato DC3000 (Pst DC3000) and Botrytis cinerea in tobacco plants. We identified a β-glucosidase named GhBGLU46 as a cotton plant target of VdSP8. VdSP8 interacts with GhBGLU46 both in vivo and in vitro and promotes the β-glucosidase activity of GhBGLU46. Silencing of GhBGLU46 reduced the expression of genes involved in lignin biosynthesis, such as GhCCR4, GhCCoAOMT2, GhCAD3 and GhCAD6, thus decreasing lignin deposition and increasing Verticillium wilt susceptibility. We have shown that GhBGLU46 is indispensable for the function of VdSP8 in plant resistance. These results suggest that plants have also evolved a strategy to exploit the invading effector protein VdSP8 to enhance plant resistance.

Leveraging transcriptomics-based approaches to enhance genomic prediction: integrating SNPs and gene networks for cotton fibre quality improvement

Cultivated cotton plants are the world's largest source of natural fibre, where yield and quality are key traits for this renewable and biodegradable commodity. The Gossypium hirsutum cotton genome contains ~80K protein-coding genes, making precision breeding of complex traits a challenge. This study tested approaches to improving the genomic prediction (GP) accuracy of valuable cotton fibre traits to help accelerate precision breeding. With a biology-informed basis, a novel approach was tested for improving GP for key cotton fibre traits with transcriptomics of key time points during fibre development, namely, fibre cells undergoing primary, transition, and secondary wall development. Three test approaches included weighting of SNPs in DE genes overall, in target DE gene lists informed by gene annotation, and in a novel approach of gene co-expression network (GCN) clusters created with partial correlation and information theory (PCIT) as the prior information in GP models. The GCN clusters were nucleated with known genes for fibre biomechanics, i.e., fasciclin-like arabinogalactan proteins, and cluster size effects were evaluated. The most promising improvements in GP accuracy were achieved by using GCN clusters for cotton fibre elongation by 4.6%, and strength by 4.7%, where cluster sizes of two and three neighbours proved most effective. Furthermore, the improvements in GP were due to only a small number of SNPs, in the order of 30 per trait using the GCN cluster approach. Non-trait-specific biological time points, and genes, were found to have neutral effects, or even reduced GP accuracy for certain traits. As the GCN clusters were generated based on known genes for fibre biomechanics, additional candidate genes were identified for fibre elongation and strength. These results demonstrate that GCN clusters make a specific and unique contribution in improving the GP of cotton fibre traits. The findings also indicate that there is room for incorporating biology-based GCNs into GP models of genomic selection pipelines for cotton breeding to help improve precision breeding of target traits. The PCIT-GCN cluster approach may also hold potential application in other crops and trees for enhancing breeding of complex traits.

Integrated transcriptomic and metabolic analyses reveal the early response mechanism of Pinus tabulaeformis to pine wood nematodes

Pine wilt disease (PWD) is a devastating disease of pine trees caused by the pine wood nematode (Bursapherenchus xylophilus, PWN). To study how Pinus tabulaeformis responds to PWD infection, we collected 3-year-old P. tabulaeformis seedlings at 2 days, 5 days, and 8 days after being infected with B. xylophilus. We identified genes and metabolites early responding to infection using transcriptome and metabolomic data obtained by high-throughput mRNA sequencing (RNA-seq) and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based assays, respectively. The following results were obtained: (1) After inoculation with PWN, the average number of days taken for 3-year-old P. tabulaeformis seedlings to develop symptoms was 8 days. (2) Combined transcriptome and metabolome analysis revealed that phenylpropanoid biosynthesis and flavonoid biosynthesis are critically important pathways for P. tabulaeformis to respond to PWD. (3) The response of P. tabulaeformis to stress was mainly through positive regulation of gene expression, including some key genes related to plant hormones or transcription factors that have been widely studied. Genes related to pathways such as photosynthesis, plant-pathogen interactions, and DNA replication were downregulated. (4) Terpenoid biosynthesis genes involved during the development of pine wilt disease. This study demonstrated the defence and pathogenic mechanisms of P. tabulaeformis against PWD, providing a reference for the early diagnosis of PWD.

GhPME36 aggravates susceptibility to Liriomyza sativae by affecting cell wall biosynthesis in cotton leaves

BACKGROUND

Cotton is an important economic crop and a host of Liriomyza sativae. Pectin methylesterase (PME)-mediated pectin metabolism plays an indispensable role in multiple biological processes in planta. However, the pleiotropic functions of PME often lead to unpredictable effects on crop resistance to pests. Additionally, whether and how PME affects susceptibility to Liriomyza sativae remain unclear.

RESULTS

Here, we isolated GhPME36, which is located in the cell wall, from upland cotton (Gossypium hirsutum L.). Interestingly, the overexpression of GhPME36 in cotton caused severe susceptibility to Liriomyza sativae but increased leaf biomass in Arabidopsis. Cytological observations revealed that the cell wall was thinner with more demethylesterified pectins in GhPME36-OE cotton leaves than in WT leaves, whereas the soluble sugar content of GhPME36-OE cotton leaf cell walls was accordingly higher; both factors attracted Liriomyza sativae to feed on GhPME36-OE cotton leaves. Metabolomic analysis demonstrated that glucose was significantly differentially accumulated. Transcriptomic analysis further revealed DEGs enriched in glucose metabolic pathways when GhPME36 was overexpressed, suggesting that GhPME36 aggravates susceptibility to Liriomyza sativae by affecting both the structure and components of cell wall biosynthesis. Moreover, GhPME36 interacts with another pectin-modifying enzyme, GhC/VIF1, to maintain the dynamic stability of pectin methyl esterification.

CONCLUSIONS

Taken together, our results reveal the cytological and molecular mechanisms by which GhPME36 aggravates susceptibility to Liriomyza sativae. This study broadens the knowledge of PME function and provides new insights into plant resistance to pests and the safety of genetically modified plants.

Vascular tissue - boon or bane? How pathogens usurp long-distance transport in plants and the defence mechanisms deployed to counteract them

Evolutionary emergence of specialised vascular tissues has enabled plants to coordinate their growth and adjust to unfavourable external conditions. Whilst holding a pivotal role in long-distance transport, both xylem and phloem can be encroached on by various biotic factors for systemic invasion and hijacking of nutrients. Therefore, a complete understanding of the strategies deployed by plants against such pathogens to restrict their entry and establishment within plant tissues, is of key importance for the future development of disease-tolerant crops. In this review, we aim to describe how microorganisms exploit the plant vascular system as a route for gaining access and control of different host tissues and metabolic pathways. Highlighting several biological examples, we detail the wide range of host responses triggered to prevent or hinder vascular colonisation and effectively minimise damage upon biotic invasions.

A novel role of the cotton calcium sensor CBL3 was involved in Verticillium wilt resistance in cotton

BACKGROUND

Verticillium wilt, causes mainly by the soilborne pathogen Verticillium dahliae, is a devastated vascular disease resulting in huge financial losses in cotton, so research on improving V. dahliae stress tolerance in cotton is the utmost importance. Calcium as the second messenger acts as a crucial role in plant innate immunity. Cytosolic Ca2+during the pathogen infection is a significant increase in plant immune responses. Calcineurin B-like (CBL) proteins are widely known calcium sensors that regulate abiotic stress responses. However, the role of cotton CBLs in response to V. dahliae stress remains unclear.

OBJECTIVE

To discover and utilize the gene to Verticillium wilt resistance and defense response mechanism of cotton.

METHODS

Through screening the gene to Verticillium wilt resistance in cotton, four GhCBL3 copies were obtained from the current common cotton genome sequences. The protein domain and phylogenetic analyses of GhCBL3 were performed using NCBI Blast, DNAMAN, and MotifScan programs. Real-time RT-PCR was used to detect the expression of GhCBL3 gene in cotton seedlings under various stress treatments. The expression construct including GhCBL3 cDNA was transduced into Agrobacterium tumefaciens (GV3101) by heat shock method and transformed into cotton plants by Virus-Induced Gene Silencing (VIGS) method. The results of silencing of GhCBl3 on ROS accumulation and plant disease resistance in cotton plants were assessed.

RESULTS

A member of calcineurin B-like proteins (defined as GhCBL3) in cotton was obtained. The expression of GhCBL3 was significantly induced and raised by various stressors, including dahliae, jasmonic acid (JA) and H2O2 stresses. Knockdown GhCBL3 in cotton by Virus-Induced Gene Silencing analysis enhanced Verticillium wilt tolerance and changed the occurrence of reactive oxygen species. Some disease-resistant genes were increased in GhCBL3-silencing cotton lines.

CONCLUSION

GhCBL3 may function on regulating the Verticillium dahliae stress response of plants.

What are the 100 most cited fungal genera?

The global diversity of fungi has been estimated between 2 to 11 million species, of which only about 155 000 have been named. Most fungi are invisible to the unaided eye, but they represent a major component of biodiversity on our planet, and play essential ecological roles, supporting life as we know it. Although approximately 20 000 fungal genera are presently recognised, the ecology of most remains undetermined. Despite all this diversity, the mycological community actively researches some fungal genera more commonly than others. This poses an interesting question: why have some fungal genera impacted mycology and related fields more than others? To address this issue, we conducted a bibliometric analysis to identify the top 100 most cited fungal genera. A thorough database search of the Web of Science, Google Scholar, and PubMed was performed to establish which genera are most cited. The most cited 10 genera are Saccharomyces, Candida, Aspergillus, Fusarium, Penicillium, Trichoderma, Botrytis, Pichia, Cryptococcus and Alternaria. Case studies are presented for the 100 most cited genera with general background, notes on their ecology and economic significance and important research advances. This paper provides a historic overview of scientific research of these genera and the prospect for further research. Citation: Bhunjun CS, Chen YJ, Phukhamsakda C, Boekhout T, Groenewald JZ, McKenzie EHC, Francisco EC, Frisvad JC, Groenewald M, Hurdeal VG, Luangsa-ard J, Perrone G, Visagie CM, Bai FY, Błaszkowski J, Braun U, de Souza FA, de Queiroz MB, Dutta AK, Gonkhom D, Goto BT, Guarnaccia V, Hagen F, Houbraken J, Lachance MA, Li JJ, Luo KY, Magurno F, Mongkolsamrit S, Robert V, Roy N, Tibpromma S, Wanasinghe DN, Wang DQ, Wei DP, Zhao CL, Aiphuk W, Ajayi-Oyetunde O, Arantes TD, Araujo JC, Begerow D, Bakhshi M, Barbosa RN, Behrens FH, Bensch K, Bezerra JDP, Bilański P, Bradley CA, Bubner B, Burgess TI, Buyck B, Čadež N, Cai L, Calaça FJS, Campbell LJ, Chaverri P, Chen YY, Chethana KWT, Coetzee B, Costa MM, Chen Q, Custódio FA, Dai YC, Damm U, de Azevedo Santiago ALCM, De Miccolis Angelini RM, Dijksterhuis J, Dissanayake AJ, Doilom M, Dong W, Alvarez-Duarte E, Fischer M, Gajanayake AJ, Gené J, Gomdola D, Gomes AAM, Hausner G, He MQ, Hou L, Iturrieta-González I, Jami F, Jankowiak R, Jayawardena RS, Kandemir H, Kiss L, Kobmoo N, Kowalski T, Landi L, Lin CG, Liu JK, Liu XB, Loizides M, Luangharn T, Maharachchikumbura SSN, Makhathini Mkhwanazi GJ, Manawasinghe IS, Marin-Felix Y, McTaggart AR, Moreau PA, Morozova OV, Mostert L, Osiewacz HD, Pem D, Phookamsak R, Pollastro S, Pordel A, Poyntner C, Phillips AJL, Phonemany M, Promputtha I, Rathnayaka AR, Rodrigues AM, Romanazzi G, Rothmann L, Salgado-Salazar C, Sandoval-Denis M, Saupe SJ, Scholler M, Scott P, Shivas RG, Silar P, Souza-Motta CM, Silva-Filho AGS, Spies CFJ, Stchigel AM, Sterflinger K, Summerbell RC, Svetasheva TY, Takamatsu S, Theelen B, Theodoro RC, Thines M, Thongklang N, Torres R, Turchetti B, van den Brule T, Wang XW, Wartchow F, Welti S, Wijesinghe SN, Wu F, Xu R, Yang ZL, Yilmaz N, Yurkov A, Zhao L, Zhao RL, Zhou N, Hyde KD, Crous PW (2024). What are the 100 most cited fungal genera? Studies in Mycology 108: 1-411. doi: 10.3114/sim.2024.108.01.

Positive roles of the Ca2+ sensors GbCML45 and GbCML50 in improving cotton Verticillium wilt resistance

As a universal second messenger, cytosolic calcium (Ca2+) functions in multifaceted intracellular processes, including growth, development and responses to biotic/abiotic stresses in plant. The plant-specific Ca2+ sensors, calmodulin and calmodulin-like (CML) proteins, function as members of the second-messenger system to transfer Ca2+ signal into downstream responses. However, the functions of CMLs in the responses of cotton (Gossypium spp.) after Verticillium dahliae infection, which causes the serious vascular disease Verticillium wilt, remain elusive. Here, we discovered that the expression level of GbCML45 was promoted after V. dahliae infection in roots of cotton, suggesting its potential role in Verticillium wilt resistance. We found that knockdown of GbCML45 in cotton plants decreased resistance while overexpression of GbCML45 in Arabidopsis thaliana plants enhanced resistance to V. dahliae infection. Furthermore, there was physiological interaction between GbCML45 and its close homologue GbCML50 by using yeast two-hybrid and bimolecular fluorescence assays, and both proteins enhanced cotton resistance to V. dahliae infection in a Ca2+-dependent way in a knockdown study. Detailed investigations indicated that several defence-related pathways, including salicylic acid, ethylene, reactive oxygen species and nitric oxide signalling pathways, as well as accumulations of lignin and callose, are responsible for GbCML45- and GbCML50-modulated V. dahliae resistance in cotton. These results collectively indicated that GbCML45 and GbCML50 act as positive regulators to improve cotton Verticillium wilt resistance, providing potential targets for exploitation of improved Verticillium wilt-tolerant cotton cultivars by genetic engineering and molecular breeding.

Unraveling verticillium wilt resistance: insight from the integration of transcriptome and metabolome in wild eggplant

Verticillium wilt, caused by Verticillium dahliae, is a soil-borne disease affecting eggplant. Wild eggplant, recognized as an excellent disease-resistant resource against verticillium wilt, plays a pivotal role in grafting and breeding for disease resistance. However, the underlying resistance mechanisms of wild eggplant remain poorly understood. This study compared two wild eggplant varieties, LC-2 (high resistance) and LC-7 (sensitive) at the phenotypic, transcriptomic, and metabolomic levels to determine the molecular basis of their resistance to verticillium wilt. These two varieties exhibit substantial phenotypic differences in petal color, leaf spines, and fruit traits. Following inoculation with V. dahliae, LC-2 demonstrated significantly higher activities of polyphenol oxidase, superoxide dismutase, peroxidase, phenylalanine ammonia lyase, β-1,3 glucanase, and chitinase than did LC-7. RNA sequencing revealed 4,017 differentially expressed genes (DEGs), with a significant portion implicated in processes associated with disease resistance and growth. These processes encompassed defense responses, cell wall biogenesis, developmental processes, and biosynthesis of spermidine, cinnamic acid, and cutin. A gene co-expression analysis identified 13 transcription factors as hub genes in modules related to plant defense response. Some genes exhibited distinct expression patterns between LC-2 and LC-7, suggesting their crucial roles in responding to infection. Further, metabolome analysis identified 549 differentially accumulated metabolites (DAMs) between LC-2 and LC-7, primarily consisting of compounds such as flavonoids, phenolic acids, lipids, and other metabolites. Integrated transcriptome and metabolome analyses revealed the association of 35 gene-metabolite pairs in modules related to the plant defense response, highlighting the interconnected processes underlying the plant defense response. These findings characterize the molecular basis of LC-2 resistance to verticillium wilt and thus have potential value for future breeding of wilt-resistant eggplant varieties.

Endophytic non-pathogenic Fusarium oxysporum reorganizes the cell wall in flax seedlings

Introduction

Flax (Linum usitatissimum) is a crop producing valuable products like seeds and fiber. However, its cultivation faces challenges from environmental stress factors and significant yield losses due to fungal infections. The major threat is Fusarium oxysporum f.sp lini, causing fusarium wilt of flax. Interestingly, within the Fusarium family, there are non-pathogenic strains known as biocontrols, which protect plants from infections caused by pathogenic strains. When exposed to a non-pathogenic strain, flax exhibits defense responses similar to those seen during pathogenic infections. This sensitization process activates immune reactions, preparing the plant to better combat potential pathogenic strains. The plant cell wall is crucial for defending against pathogens. It serves as the primary barrier, blocking pathogen entry into plant cells.

Methods

The aim of the study was to investigate the effects of treating flax with a non-pathogenic Fusarium oxysporum strain, focusing on cell wall remodeling. The infection's progress was monitored by determining the fungal DNA content and microscopic observation. The plant defense response was confirmed by an increase in the level of Pathogenesis-Related (PR) genes transcripts. The reorganization of flax cell wall during non-pathogenic Fusarium oxysporum strain infection was examined using Infrared spectroscopy (IR), determination of cell wall polymer content, and analysis of mRNA level of genes involved in their metabolism.

Results and discussion

IR analysis revealed reduced cellulose content in flax seedlings after treatment with Fo47 and that the cellulose chains were shorter and more loosely bound. Hemicellulose content was also reduced but only after 12h and 36h. The total pectin content remained unchanged, while the relative share of simple sugars and uronic acids in the pectin fractions changed over time. In addition, a dynamic change in the level of methylesterification of carboxyl groups of pectin was observed in flax seedlings treated with Fo47 compared to untreated seedlings. The increase in lignin content was observed only 48 hours after the treatment with non-pathogenic Fusarium oxysporum. Analysis of mRNA levels of cell wall polymer metabolism genes showed significant changes over time in all analyzed genes. In conclusion, the research suggests that the rearrangement of the cell wall is likely one of the mechanisms behind flax sensitization by the non-pathogenic Fusarium oxysporum strain. Understanding these processes could help in developing strategies to enhance flax's resistance to fusarium wilt and improve its overall yield and quality.

Histological, chemical and gene expression differences between western redcedar seedlings resistant and susceptible to cedar leaf blight

Introduction

Western redcedar (Thuja plicata) is an important species in the Cupressaceae both at economic and cultural levels in the Pacific Northwest of North America. In adult trees, the species produces one of the most weathering-resistant heartwoods among conifers, making it one of the preferred species for outdoor applications. However, young T. plicata plants are susceptible to infection with cedar leaf blight (Didymascella thujina), an important foliar pathogen that can be devastating in nurseries and small-spaced plantations. Despite that, variability in the resistance against D. thujina in T. plicata has been documented, and such variability can be used to breed T. plicata for resistance against the pathogen.

Objective

This investigation aimed to discern the phenotypic and gene expression differences between resistant and susceptible T. plicata seedlings to shed light on the potential constitutive resistance mechanisms against cedar leaf blight in western redcedar.

Methods

The study consisted of two parts. First, the histological differences between four resistant and four susceptible families that were never infected with the pathogen were investigated. And second, the differences between one resistant and one susceptible family that were infected and not infected with the pathogen were analyzed at the chemical (C, N, mineral nutrients, lignin, fiber, starch, and terpenes) and gene expression (RNA-Seq) levels.

Results

The histological part showed that T. plicata seedlings resistant to D. thujina had constitutively thicker cuticles and lower stomatal densities than susceptible plants. The chemical analyses revealed that, regardless of their infection status, resistant plants had higher foliar concentrations of sabinene and α-thujene, and higher levels of expression of transcripts that code for leucine-rich repeat receptor-like protein kinases and for bark storage proteins.

Conclusion

The data collected in this study shows that constitutive differences at the phenotypic (histological and chemical) and gene expression level exist between T. plicata seedlings susceptible and resistant to D. thujina. Such differences have potential use for marker-assisted selection and breeding for resistance against cedar leaf blight in western redcedar in the future.

The elicitor VP2 from Verticillium dahliae triggers defence response in cotton

Verticillium dahliae is a widespread and destructive soilborne vascular pathogenic fungus that causes serious diseases in dicot plants. Here, comparative transcriptome analysis showed that the number of genes upregulated in defoliating pathotype V991 was significantly higher than in the non-defoliating pathotype 1cd3-2 during the early response of cotton. Combined with analysis of the secretome during the V991-cotton interaction, an elicitor VP2 was identified, which was highly upregulated at the early stage of V991 invasion, but was barely expressed during the 1cd3-2-cotton interaction. Full-length VP2 could induce cell death in several plant species, and which was dependent on NbBAK1 but not on NbSOBIR1 in N. benthamiana. Knock-out of VP2 attenuated the pathogenicity of V991. Furthermore, overexpression of VP2 in cotton enhanced resistance to V. dahliae without causing abnormal plant growth and development. Several genes involved in JA, SA and lignin synthesis were significantly upregulated in VP2-overexpressing cotton. The contents of JA, SA, and lignin were also significantly higher than in the wild-type control. In summary, the identified elicitor VP2, recognized by the receptor in the plant membrane, triggers the cotton immune response and enhances disease resistance.

Harnessing root exudates for plant microbiome engineering and stress resistance in plants

A wide range of abiotic and biotic stresses adversely affect plant's growth and production. Under stress, one of the main responses of plants is the modulation of exudates excreted in the rhizosphere, which consequently leads to alterations in the resident microbiota. Thus, the exudates discharged into the rhizospheric environment play a preponderant role in the association and formation of plant-microbe interactions. In this review, we aimed to provide a synthesis of the latest and most pertinent literature on the diverse biochemical and structural compositions of plant root exudates. Also, this work investigates into their multifaceted role in microbial nutrition and intricate signaling processes within the rhizosphere, which includes quorum-sensing molecules. Specifically, it explores the contributions of low molecular weight compounds, such as carbohydrates, phenolics, organic acids, amino acids, and secondary metabolites, as well as the significance of high molecular weight compounds, including proteins and polysaccharides. It also discusses the state-of-the-art omics strategies that unveil the vital role of root exudates in plant-microbiome interactions, including defense against pathogens like nematodes and fungi. We propose multiple challenges and perspectives, including exploiting plant root exudates for host-mediated microbiome engineering. In this discourse, root exudates and their derived interactions with the rhizospheric microbiota should receive greater attention due to their positive influence on plant health and stress mitigation.

Transcriptomic insights into the molecular mechanism for response of wild emmer wheat to stripe rust fungus

Introduction

Continuous identification and application of novel resistance genes against stripe rust are of great importance for wheat breeding. Wild emmer wheat, Triticum dicoccoides, has adapted to a broad range of environments and is a valuable genetic resource that harbors important beneficial traits, including resistance to stripe rust caused by Puccinia striiformis f. sp. tritici (Pst). However, there has been a lack of systematic exploration of genes against Pst races in wild emmer wheat.

Methods

Genome-wide transcriptome profiles were conducted on two wild emmer wheat genotypes with different levels of resistance to (Pst (DR3 exhibiting moderate (Pst resistance, and D7 displaying high (Pst resistance). qRT-PCR was performed to verify findings by RNA-seq.

Results

A higher number of DEGs were identified in the moderately (Pst-resistant genotype, while the highly (Pst-resistant genotype exhibited a greater enrichment of pathways. Nonetheless, there were consistent patterns in the enrichment of pathways between the two genotypes at the same time of inoculation. At 24 hpi, a majority of pathways such as the biosynthesis of secondary metabolites, phenylpropanoid biosynthesis, phenylalanine metabolism, and alpha-Linolenic acid metabolism exhibited significant enrichment in both genotypes. At 72 hpi, the biosynthesis of secondary metabolites and circadian rhythm-plant pathways were notably and consistently enriched in both genotypes. The majority of (WRKY, MADs , and AP2-ERF families were found to be involved in the initial stage of response to Pst invasion (24 hpi), while the MYB, NAC, TCP, and b-ZIP families played a role in defense during the later stage of Pst infection (72 hpi).

Discussion

In this present study, we identified numerous crucial genes, transcription factors, and pathways associated with the response and regulation of wild emmer wheat to Pst infection. Our findings offer valuable information for understanding the function of crucial Pst-responsive genes, and will deepen the understanding of the complex resistance mechanisms against Pst in wheat.

Transcriptomic datasets of Verticillium wilt resistant and non-resistant Gossypium barbadense varieties during pathogen inoculation

Cotton is a significant cash crop and the primary source of natural fiber globally. Among the numerous diseases encountered in cotton production, Verticillium wilt is one of the most serious, caused by the pathogen Verticillium dahliae (V. dahliae). Unfortunately, there are no effective targeted methods to combat this disease. Genomic resources for Verticillium wilt resistance primarily exist in Gossypium barbadense (G. barbadense). Regrettably, there have been limited transcriptomic comparisons between V. dahliae-resistant and -susceptible varieties of G. barbadense due to the scarcity of susceptible resources. In this study, we conducted a transcriptome analysis on both V. dahliae-resistant and -susceptible varieties of G. barbadense at the 0, 12, 24 and 48 hours after V. dahliae inoculation. This comparative transcriptome analysis yielded high-quality data and offered new insights into the molecular mechanisms underlying cotton's resistance against this destructive pathogen.

Seed biopriming with Ochrobactrum ciceri mediated defense responses in Zea mays (L.) against Fusarium rot

Seed bio-priming is a simple and friendly technique to improve stress resilience against fungal diseases in plants. An integrated approach of maize seeds biopriming with Ochrobactrum ciceri was applied in Zn-amended soil to observe the response against Fusarium rot disease of Zea mays (L.) caused by Fusarium verticillioides. Initially, the pathogen isolated from the infected corn was identified as F. verticillioides based on morphology and sequences of the internally transcribed spacer region of the ribosomal RNA gene. Re-inoculation of maize seed with the isolated pathogen confirmed the pathogenicity of the fungus on the maize seeds. In vitro, the inhibitory potential of O. ciceri assessed on Zn-amended/un-amended growth medium revealed that antifungal potential of O. ciceri significantly improved in the Zn-amended medium, leading to 88% inhibition in fungal growth. Further assays with different concentrations (25, 50, and 75%) of cell pellet and the cultural filtrate of O. ciceri (with/without the Zn-amendment) showed a dose-dependent inhibitory effect on mycelial growth of the pathogen that also led to discoloration, fragmentation, and complete disintegration of the fungus hyphae and spores at 75% dose. In planta, biopriming of maize seeds with O. ciceri significantly managed disease, improved the growth and biochemical attributes (up to two-fold), and accelerated accumulation of lignin, polyphenols, and starch, especially in the presence of basal Zn. The results indicated that bioprimed seeds along with Zn as the most promising treatment for managing disease and improving plant growth traits through the enhanced accumulation of lignin, polyphenols, and starch, respectively.

Transcriptomic and metabolomic analyses reveals keys genes and metabolic pathways in tea (Camellia sinensis) against six-spotted spider mite (Eotetranychus Sexmaculatus)

BACKGROUND

Six-spotted spider mite (Eotetranychus sexmaculatus) is one of the most damaging pests of tea (Camellia sinensis). E. sexmaculatus causes great economic loss and affects tea quality adversely. In response to pests, such as spider mites, tea plants have evolved resistance mechanisms, such as expression of defense-related genes and defense-related metabolites.

RESULTS

To evaluate the biochemical and molecular mechanisms of resistance in C. sinensis against spider mites, "Tianfu-5" (resistant to E. sexmaculatus) and "Fuding Dabai" (susceptible to E. sexmaculatus) were inoculated with spider mites. Transcriptomics and metabolomics based on RNA-Seq and liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) technology were used to analyze changes in gene expression and metabolite content, respectively. RNA-Seq data analysis revealed that 246 to 3,986 differentially expressed genes (DEGs) were identified in multiple compared groups, and these DEGs were significantly enriched in various pathways, such as phenylpropanoid and flavonoid biosynthesis, plant-pathogen interactions, MAPK signaling, and plant hormone signaling. Additionally, the metabolome data detected 2,220 metabolites, with 194 to 260 differentially abundant metabolites (DAMs) identified in multiple compared groups, including phenylalanine, lignin, salicylic acid, and jasmonic acid. The combined analysis of RNA-Seq and metabolomic data indicated that phenylpropanoid and flavonoid biosynthesis, MAPK signaling, and Ca2+-mediated PR-1 signaling pathways may contribute to spider mite resistance.

CONCLUSIONS

Our findings provide insights for identifying insect-induced genes and metabolites and form a basis for studies on mechanisms of host defense against spider mites in C. sinensis. The candidate genes and metabolites identified will be a valuable resource for tea breeding in response to biotic stress.

Polyethyleneimine-coated MXene quantum dots improve cotton tolerance to Verticillium dahliae by maintaining ROS homeostasis

Verticillium dahliae is a soil-borne hemibiotrophic fungal pathogen that threatens cotton production worldwide. In this study, we assemble the genomes of two V. dahliae isolates: the more virulence and defoliating isolate V991 and nondefoliating isolate 1cd3-2. Transcriptome and comparative genomics analyses show that genes associated with pathogen virulence are mostly induced at the late stage of infection (Stage II), accompanied by a burst of reactive oxygen species (ROS), with upregulation of more genes involved in defense response in cotton. We identify the V991-specific virulence gene SP3 that is highly expressed during the infection Stage II. V. dahliae SP3 knock-out strain shows attenuated virulence and triggers less ROS production in cotton plants. To control the disease, we employ polyethyleneimine-coated MXene quantum dots (PEI-MQDs) that possess the ability to remove ROS. Cotton seedlings treated with PEI-MQDs are capable of maintaining ROS homeostasis with enhanced peroxidase, catalase, and glutathione peroxidase activities and exhibit improved tolerance to V. dahliae. These results suggest that V. dahliae trigger ROS production to promote infection and scavenging ROS is an effective way to manage this disease. This study reveals a virulence mechanism of V. dahliae and provides a means for V. dahliae resistance that benefits cotton production.

Candidate genes for field resistance to cassava brown streak disease revealed through the analysis of multiple data sources

Cassava (Manihot esculenta Crantz) is a food and industrial storage root crop with substantial potential to contribute to managing risk associated with climate change due to its inherent resilience and in providing a biodegradable option in manufacturing. In Africa, cassava production is challenged by two viral diseases, cassava brown streak disease (CBSD) and cassava mosaic disease. Here we detect quantitative trait loci (QTL) associated with CBSD in a biparental mapping population of a Tanzanian landrace, Nachinyaya and AR37-80, phenotyped in two locations over three years. The purpose was to use the information to ultimately facilitate either marker-assisted selection or adjust weightings in genomic selection to increase the efficiency of breeding. Results from this study were considered in relation to those from four other biparental populations, of similar genetic backgrounds, that were phenotyped and genotyped simultaneously. Further, we investigated the co-localization of QTL for CBSD resistance across populations and the genetic relationships of parents based on whole genome sequence information. Two QTL on chromosome 4 for resistance to CBSD foliar symptoms and one on each of chromosomes 11 and 18 for root necrosis were of interest. Of significance within the candidate genes underlying the QTL on chromosome 4 are Phenylalanine ammonia-lyase (PAL) and Cinnamoyl-CoA reductase (CCR) genes and three PEPR1-related kinases associated with the lignin pathway. In addition, a CCR gene was also underlying the root necrosis-resistant QTL on chromosome 11. Upregulation of key genes in the cassava lignification pathway from an earlier transcriptome study, including PAL and CCR, in a CBSD-resistant landrace compared to a susceptible landrace suggests a higher level of basal lignin deposition in the CBSD-resistant landrace. Earlier RNAscope® in situ hybridisation imaging experiments demonstrate that cassava brown streak virus (CBSV) is restricted to phloem vessels in CBSV-resistant varieties, and phloem unloading for replication in mesophyll cells is prevented. The results provide evidence for the involvement of the lignin pathway. In addition, five eukaryotic initiation factor (eIF) genes associated with plant virus resistance were found within the priority QTL regions.

Transcriptomic Analysis of the Response of Susceptible and Resistant Bitter Melon (Momordica charantia L.) to Powdery Mildew Infection Revealing Complex Resistance via Multiple Signaling Pathways

The challenge of mitigating the decline in both yield and fruit quality due to the intrusion of powdery mildew (PM) fungus looms as a pivotal concern in the domain of bitter melon cultivation. Yet, the intricate mechanisms that underlie resistance against this pathogen remain inscrutable for the vast majority of bitter melon variants. In this inquiry, we delve deeply into the intricate spectrum of physiological variations and transcriptomic fluctuations intrinsic to the PM-resistant strain identified as '04-17-4' (R), drawing a sharp contrast with the PM-susceptible counterpart, designated as '25-15' (S), throughout the encounter with the pathogenic agent Podosphaera xanthii. In the face of the challenge presented by P. xanthii, the robust cultivar displays an extraordinary capacity to prolong the initiation of the pathogen's primary growth stage. The comprehensive exploration culminates in the discernment of 6635 and 6954 differentially expressed genes (DEGs) in R and S strains, respectively. Clarification through the lens of enrichment analyses reveals a prevalence of enriched DEGs in pathways interconnected with phenylpropanoid biosynthesis, the interaction of plants with pathogens, and the signaling of plant hormones. Significantly, in the scope of the R variant, DEGs implicated in the pathways of plant-pathogen interaction phenylpropanoid biosynthesis, encompassing components such as calcium-binding proteins, calmodulin, and phenylalanine ammonia-lyase, conspicuously exhibit an escalated tendency upon the encounter with P. xanthii infection. Simultaneously, the genes governing the synthesis and transduction of SA undergo a marked surge in activation, while their counterparts in the JA signaling pathway experience inhibition following infection. These observations underscore the pivotal role played by SA/JA signaling cascades in choreographing the mechanism of resistance against P. xanthii in the R variant. Moreover, the recognition of 40 P. xanthii-inducible genes, encompassing elements such as pathogenesis-related proteins, calmodulin, WRKY transcription factors, and Downy mildew resistant 6, assumes pronounced significance as they emerge as pivotal contenders in the domain of disease control. The zenith of this study harmonizes multiple analytical paradigms, thus capturing latent molecular participants and yielding seminal resources crucial for the advancement of PM-resistant bitter melon cultivars.

Uncovering genomic and transcriptional variations facilitates utilization of wild resources in cotton disease resistance improvement

BACKGROUND

Upland cotton wild/landraces represent a valuable resource for disease resistance alleles. Genetic differentiation between genotypes, as well as variation in Verticillium wilt (VW) resistance, has been poorly characterized for upland cotton accessions on the domestication spectrum (from wild/landraces to elite lines).

RESULTS

To illustrate the effects of modern breeding on VW resistance in upland cotton, 37 wild/landraces were resequenced and phenotyped for VW resistance. Genomic patterns of differentiation were identified between wild/landraces and improved upland cotton, and a significant decline in VW resistance was observed in association with improvement. Four genotypes representing different degrees of improvement were used in a full-length transcriptome analysis to study the genetic basis of VW resistance. ROS signaling was highly conserved at the transcriptional level, likely providing the basis for VW resistance in upland cotton. ASN biosynthesis and HSP90-mediated resistance moderated the response to VW in wild/landraces, and loss of induction activity of these genes resulted in VW susceptibility. The observed genomic differentiation contributed to the loss of induction of some important VW resistance genes such as HSP90.4 and PR16.

CONCLUSIONS

Besides providing new insights into the evolution of upland cotton VW resistance, this study also identifies important resistance pathways and genes for both fundamental research and cotton breeding.

Tissues and mechanisms associated with Verticillium wilt resistance in tomato using bi-grafted near-isogenic lines

Host resistance is the primary means to control Verticillium dahliae, a soil-borne pathogen causing major losses on a broad range of plants, including tomato. The tissues and mechanisms responsible for resistance remain obscure. In the field, resistant tomato used as rootstocks does not confer resistance. Here, we created bi-grafted plants with near-isogenic lines (NILs) exhibiting (Ve1) or lacking (ve1) resistance to V. dahliae race 1. Ten days after inoculation, scion and rootstock tissues were subjected to differential gene expression and co-expression network analyses. Symptoms only developed in susceptible scions regardless of the rootstock. Infection caused more dramatic alteration of tomato gene expression in susceptible compared with resistant tissues, including pathogen receptor, signaling pathway, pathogenesis-related protein, and cell wall modification genes. Differences were observed between scions and rootstocks, primarily related to physiological processes in these tissues. Gene expression in scions was influenced by the rootstock genotype. A few genes were associated with the Ve1 genotype, which was independent of infection or tissue type. Several were physically clustered, some near the Ve1 locus on chromosome 9. Transcripts mapped to V. dahliae were dominated by secreted candidate effector proteins. These findings advance knowledge of molecular mechanisms underlying the tomato-V. dahliae interaction.

Genome-wide identification and analysis of a cotton secretome reveals its role in resistance against Verticillium dahliae

BACKGROUND

The extracellular space between the cell wall and plasma membrane is a battlefield in plant-pathogen interactions. Within this space, the pathogen employs its secretome to attack the host in a variety of ways, including immunity manipulation. However, the role of the plant secretome is rarely studied for its role in disease resistance.

RESULTS

Here, we examined the secretome of Verticillium wilt-resistant Gossypium hirsutum cultivar Zhongzhimian No.2 (ZZM2, encoding 95,327 predicted coding sequences) to determine its role in disease resistance against the wilt causal agent, Verticillium dahliae. Bioinformatics-driven analyses showed that the ZZM2 genome encodes 2085 secreted proteins and that these display disequilibrium in their distribution among the chromosomes. The cotton secretome displayed differences in the abundance of certain amino acid residues as compared to the remaining encoded proteins due to the localization of these putative proteins in the extracellular space. The secretome analysis revealed conservation for an allotetraploid genome, which nevertheless exhibited variation among orthologs and comparable unique genes between the two sub-genomes. Secretome annotation strongly suggested its involvement in extracellular stress responses (hydrolase activity, oxidoreductase activity, and extracellular region, etc.), thus contributing to resistance against the V. dahliae infection. Furthermore, the defense response genes (immunity marker NbHIN1, salicylic acid marker NbPR1, and jasmonic acid marker NbLOX4) were activated to varying degrees when Nicotina benthamiana leaves were agro-infiltrated with 28 randomly selected members, suggesting that the secretome plays an important role in the immunity response. Finally, gene silencing assays of 11 members from 13 selected candidates in ZZM2 displayed higher susceptibility to V. dahliae, suggesting that the secretome members confer the Verticillium wilt resistance in cotton.

CONCLUSIONS

Our data demonstrate that the cotton secretome plays an important role in Verticillium wilt resistance, facilitating the development of the resistance gene markers and increasing the understanding of the mechanisms regulating disease resistance.

Profile of cotton flavonoids: Their composition and important roles in development and adaptation to adverse environments

Cotton is a commercial crop that is cultivated in more than 50 countries. The production of cotton has severely diminished in recent years owing to adverse environments. Thus, it is a high priority of the cotton industry to produce resistant cultivars to prevent diminished cotton yields and quality. Flavonoids comprise one of the most important groups of phenolic metabolites in plants. However, the advantage and biological roles of flavonoids in cotton have yet not been studied in depth. In this study, we performed a widely targeted metabolic study and identified 190 flavonoids in cotton leaves that span seven different classes with flavones and flavonols as the dominant groups. Furthermore, flavanone-3-hydroxylase was cloned and silenced to knock down flavonoid production. The results show that the inhibition of flavonoid biosynthesis affects the growth and development of cotton and causes semi-dwarfing in cotton seedlings. We also revealed that the flavonoids contribute to cotton defense against ultraviolet radiation and Verticillium dahliae. Moreover, we discuss the promising role of flavonoids in cotton development and defense against biotic and abiotic stresses. This study provides valuable information to study the variety and biological functions of flavonoids in cotton and will help to profile the advantages of flavonoids in cotton breeding.

Unraveling genomic regions and candidate genes for multiple disease resistance in upland cotton using meta-QTL analysis

Verticillium wilt (VW), Fusarium wilt (FW) and Root-knot nematode (RKN) are the main diseases affecting cotton production. However, many reported quantitative trait loci (QTLs) for cotton resistance have not been used for agricultural practices because of inconsistencies in the cotton genetic background. The integration of existing cotton genetic resources can facilitate the discovery of important genomic regions and candidate genes involved in disease resistance. Here, an improved and comprehensive meta-QTL analysis was conducted on 487 disease resistant QTLs from 31 studies in the last two decades. A consensus linkage map with genetic overall length of 3006.59 cM containing 8650 markers was constructed. A total of 28 Meta-QTLs (MQTLs) were discovered, among which nine MQTLs were identified as related to resistance to multiple diseases. Candidate genes were predicted based on public transcriptome data and enriched in pathways related to disease resistance. This study used a method based on the integration of Meta-QTL, known genes and transcriptomics to reveal major genomic regions and putative candidate genes for resistance to multiple diseases, providing a new basis for marker-assisted selection of high disease resistance in cotton breeding.

Comparative Transcriptome Profiling of CMS-D2 and CMS-D8 Systems Characterizes Fertility Restoration Genes Network in Upland Cotton

Resolving the genetic basis of fertility restoration for cytoplasmic male sterility (CMS) can improve the efficiency of three-line hybrid breeding. However, the genetic determinants of male fertility restoration in cotton are still largely unknown. This study comprehensively compared the full-length transcripts of CMS-D2 and CMS-D8 systems to identify potential genes linked with fertility restorer genes Rf₁ or Rf₂. Target comparative analysis revealed a higher percentage of differential genes in each restorer line as compared to their corresponding sterile and maintainer lines. An array of genes with specific expression in the restorer line of CMS-D2 had functional annotations related to floral development and pathway enrichments in various secondary metabolites, while specifically expressed genes in the CMS-D8 restorer line showed functional annotations related to anther development and pathway enrichment in the biosynthesis of secondary metabolites. Further analysis identified potentially key genes located in the target region of fertility restorer genes Rf₁ or Rf₂. In particular, Ghir_D05G032450 can be the candidate gene related to restorer gene Rf₁, and Ghir_D05G035690 can be the candidate gene associated with restorer gene Rf₂. Further gene expression validation with qRT-PCR confirmed the accuracy of our results. Our findings provide useful insights into decoding the potential regulatory network that retrieves pollen fertility in cotton and will help to further reveal the differences in the genetic basis of fertility restoration for two CMS systems.

Ca2+-responsive phospholipid-binding BONZAI genes confer a novel role for cotton resistance to Verticillium wilt

Verticillium wilt which produced by the soil-borne fungus Verticillium dahliae is an important biotic threat that limits cotton (Gossypium hirsutum) growth and agricultural productivity. It is very essential to explore new genes for the generation of V. dahliae resistance or tolerance cotton varieties. Ca²⁺ signaling as a secondary messenger is involved in pathogen stress response. Despite Ca²⁺-responsive phospholipid-binding BONZAI (BON) genes have intensively been investigated in Arabidopsis, their function has not still been characterized in cotton. Here, we showed that three copies of GhBON1, two copies of GhBON2 and GhBON3 were found from the genome sequences of upland cotton. The expression of GhBON1 was inducible to V. dahliae. Knocking down of GhBON1, GhBON2 and GhBON3 using virus induced gene silencing (VIGS) each increased up-regulation of defense responses in cotton. These GhBON1, GhBON2 and GhBON3-silenced plants enhanced resistance to V. dahliae accompanied by higher burst of hydrogen peroxide and decreased cell death and had more effect on the up-regulation of defense response genes. Further analysis revealed that GhBON1 could interacts with BAK1-interacting receptor-like kinase 1 (GhBIR1) and pathogen-associated molecular pattern (PAMP) receptor regulator BAK1 (GhBAK1) at plasma membrane. Our study further reveals that plant Ca²⁺ -responsive phospholipid-binding BONZAI genes negatively regulate Verticillium wilt with the conserved function in response to disease resistance or plant immunity.

Genome-wide identification of xylan glucuronosyltransferase family in cotton and function characterization of GhGUX5 in regulating Verticillium wilt resistance

Xylan glucuronosyltransferase (GUX) is widely involved in a variety of physiological processes in plants, including plant development, growth and the defense response to pathogens. However, the function of GUX regulators in Verticillium dahliae (V. dahliae) infection has not been considered previously in cotton. Overall, 119 GUX genes were identified from multiple species and were phylogenetically categorized into seven classes. Duplication event analysis indicated that GUXs in Gossypium hirsutum primarily originated from segmental duplication. GhGUXs promoter analysis indicated cis-regulatory elements capable of reacting to several different stresses. RNA-Seq data and qRT-PCR analysis both indicated that most GhGUXs were associated with V. dahliae infection. Gene interaction network analysis showed that GhGUX5 interacted with 11 proteins, and the relative expression of these 11 proteins changed significantly following V. dahliae infection. In addition, silencing and overexpression of GhGUX5 results to enhance and reduce plant's susceptibility to V. dahliae. Further study showed that TRV: GhGUX5 silenced cotton plants exhibited a decrease in the degree of lignification, total lignin content, gene expression levels involved in lignin biosynthesis, and enzyme activity compared with TRV: 00. The above results indicate that GhGUX5 enhances Verticillium wilt resistance through the lignin biosynthesis pathway.

ZmDRR206 Regulates Nutrient Accumulation in Endosperm through Its Role in Cell Wall Biogenesis during Maize Kernel Development

Dirigent proteins (DIRs) contribute to plant fitness by dynamically reorganizing the cell wall and/or by generating defense compounds during plant growth, development, and interactions with environmental stresses. ZmDRR206 is a maize DIR, it plays a role in maintaining cell wall integrity during seedling growth and defense response in maize, but its role in regulating maize kernel development is unclear. Association analysis of candidate genes indicated that the natural variations of ZmDRR206 were significantly associated with maize hundred-kernel weight (HKW). ZmDRR206 plays a dominant role in storage nutrient accumulation in endosperm during maize kernel development, ZmDRR206 overexpression resulted in small and shrunken maize kernel with significantly reduced starch content and significantly decreased HKW. Cytological characterization of the developing maize kernels revealed that ZmDRR206 overexpression induced dysfunctional basal endosperm transfer layer (BETL) cells, which were shorter with less wall ingrowth, and defense response was constitutively activated in developing maize kernel at 15 and 18 DAP by ZmDRR206 overexpression. The BETL-development-related genes and auxin signal-related genes were down-regulated, while cell wall biogenesis-related genes were up-regulated in developing BETL of the ZmDRR206-overexpressing kernel. Moreover, the developing ZmDRR206-overexpressing kernel had significantly reduced contents of the cell wall components such as cellulose and acid soluble lignin. These results suggest that ZmDRR206 may play a regulatory role in coordinating cell development, storage nutrient metabolism, and stress responses during maize kernel development through its role in cell wall biogenesis and defense response, and provides new insights into understanding the mechanisms of kernel development in maize.

GhWRKY41 forms a positive feedback regulation loop and increases cotton defence response against Verticillium dahliae by regulating phenylpropanoid metabolism

Despite the established significance of WRKY proteins and phenylpropanoid metabolism in plant immunity, how WRKY proteins modulate aspects of the phenylpropanoid pathway remains undetermined. To understand better the role of WRKY proteins in plant defence, we identified a cotton (Gossypium hirsutum) protein, GhWRKY41, that is, universally and rapidly induced in three disease-resistant cotton cultivars following inoculation with the plant pathogenic fungus, Verticillium dahliae. We show that overexpression of GhWRKY41 in transgenic cotton and Arabidopsis enhances resistance to V. dahliae, while knock-down increases cotton more susceptibility to the fungus. GhWRKY41 physically interacts with itself and directly activates its own transcription. A genome-wide chromatin immunoprecipitation and high-throughput sequencing (ChIP-seq), in combination with RNA sequencing (RNA-seq) analyses, revealed that 43.1% of GhWRKY41-binding genes were up-regulated in cotton upon inoculation with V. dahliae, including several phenylpropanoid metabolism master switches, receptor kinases, and disease resistance-related proteins. We also show that GhWRKY41 homodimer directly activates the expression of GhC4H and Gh4CL, thereby modulating the accumulation of lignin and flavonoids. This finding expands our understanding of WRKY-WRKY protein interactions and provides important insights into the regulation of the phenylpropanoid pathway in plant immune responses by a WRKY protein.

Insights to Gossypium defense response against Verticillium dahliae: the Cotton Cancer

The soil-borne pathogen Verticillium dahliae, also referred as "The Cotton Cancer," is responsible for causing Verticillium wilt in cotton crops, a destructive disease with a global impact. To infect cotton plants, the pathogen employs multiple virulence mechanisms such as releasing enzymes that degrade cell walls, activating genes that contribute to virulence, and using protein effectors. Conversely, cotton plants have developed numerous defense mechanisms to combat the impact of V. dahliae. These include strengthening the cell wall by producing lignin and depositing callose, discharging reactive oxygen species, and amassing hormones related to defense. Despite the efforts to develop resistant cultivars, there is still no permanent solution to Verticillium wilt due to a limited understanding of the underlying molecular mechanisms that drive both resistance and pathogenesis is currently prevalent. To address this challenge, cutting-edge technologies such as clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), host-induced gene silencing (HIGS), and gene delivery via nano-carriers could be employed as effective alternatives to control the disease. This article intends to present an overview of V. dahliae virulence mechanisms and discuss the different cotton defense mechanisms against Verticillium wilt, including morphophysiological and biochemical responses and signaling pathways including jasmonic acid (JA), salicylic acid (SA), ethylene (ET), and strigolactones (SLs). Additionally, the article highlights the significance of microRNAs (miRNAs), circular RNAs (circRNAs), and long non-coding RNAs (lncRNAs) in gene expression regulation, as well as the different methods employed to identify and functionally validate genes to achieve resistance against this disease. Gaining a more profound understanding of these mechanisms could potentially result in the creation of more efficient strategies for combating Verticillium wilt in cotton crops.

Cotton 4-coumarate-CoA ligase 3 enhanced plant resistance to Verticillium dahliae by promoting jasmonic acid signaling-mediated vascular lignification and metabolic flux

Lignins and their antimicrobial-related polymers cooperatively enhance plant resistance to pathogens. Several isoforms of 4-coumarate-coenzyme A ligases (4CLs) have been identified as indispensable enzymes involved in lignin and flavonoid biosynthetic pathways. However, their roles in plant-pathogen interaction are still poorly understood. This study uncovers the role of Gh4CL3 in cotton resistance to the vascular pathogen Verticillium dahliae. The cotton 4CL3-CRISPR/Cas9 mutant (CR4cl) exhibited high susceptibility to V. dahliae. This susceptibility was most probably due to the reduction in the total lignin content and the biosynthesis of several phenolic metabolites, e.g., rutin, catechin, scopoletin glucoside, and chlorogenic acid, along with jasmonic acid (JA) attenuation. These changes were coupled with a significant reduction in 4CL activity toward p-coumaric acid substrate, and it is likely that recombinant Gh4CL3 could specifically catalyze p-coumaric acid to form p-coumaroyl-coenzyme A. Thus, overexpression of Gh4CL3 (OE4CL) showed increasing 4CL activity that augmented phenolic precursors, cinnamic, p-coumaric, and sinapic acids, channeling into lignin and flavonoid biosyntheses and enhanced resistance to V. dahliae. Besides, Gh4CL3 overexpression activated JA signaling that instantly stimulated lignin deposition and metabolic flux in response to pathogen, which all established an efficient plant defense response system, and inhibited V. dahliae mycelium growth. Our results propose that Gh4CL3 acts as a positive regulator for cotton resistance against V. dahliae by promoting JA signaling-mediated enhanced cell wall rigidity and metabolic flux.

Characterization of plant laccase genes and their functions

Laccase is a copper-containing polyphenol oxidase found in different organisms. The multigene family that encodes laccases is widely distributed in plant genomes. Plant laccases oxidize monolignols to produce lignin which is important for plant growth and stress responses. Industrial applications of fungal and bacterial laccases are extensively explored and addressed. Recently many studies have focused on the significance of plant laccase, particularly in crop yield, and its functions in different environmental conditions. This review summarizes the transcriptional and posttranscriptional regulation of plant laccase genes and their functions in plant growth and development. It especially describes the responses of laccase genes to various stresses and their contributions to plant biotic and abiotic stress resistance. In-depth explanations and scientific advances will serve as foundations for research into plant laccase genes' function, mechanism, and possible applications.

Interactions between Verticillium dahliae and cotton: pathogenic mechanism and cotton resistance mechanism to Verticillium wilt

Cotton is widely grown in many countries around the world due to the huge economic value of the total natural fiber. Verticillium wilt, caused by the soil-borne pathogen Verticillium dahliae, is the most devastating disease that led to extensive yield losses and fiber quality reduction in cotton crops. Developing resistant cotton varieties through genetic engineering is an effective, economical, and durable strategy to control Verticillium wilt. However, there are few resistance gene resources in the currently planted cotton varieties, which has brought great challenges and difficulties for breeding through genetic engineering. Further revealing the molecular mechanism between V. dahliae and cotton interaction is crucial to discovering genes related to disease resistance. In this review, we elaborated on the pathogenic mechanism of V. dahliae and the resistance mechanism of cotton to Verticillium wilt. V. dahliae has evolved complex mechanisms to achieve pathogenicity in cotton, mainly including five aspects: (1) germination and growth of microsclerotia; (2) infection and successful colonization; (3) adaptation to the nutrient-deficient environment and competition of nutrients; (4) suppression and manipulation of cotton immune responses; (5) rapid reproduction and secretion of toxins. Cotton has evolved multiple physiological and biochemical responses to cope with V. dahliae infection, including modification of tissue structures, accumulation of antifungal substances, homeostasis of reactive oxygen species (ROS), induction of Ca²⁺ signaling, the mitogen-activated protein kinase (MAPK) cascades, hormone signaling, and PAMPs/effectors-triggered immune response (PTI/ETI). This review will provide an important reference for the breeding of new cotton germplasm resistant to Verticillium wilt through genetic engineering.

The ScAPD1-like gene from the desert moss Syntrichia caninervis enhances resistance to Verticillium dahliae via phenylpropanoid gene regulation

Soloist is a member of a distinct and small subfamily within the AP2/ERF transcriptional factor family that play important roles in plant biotic and abiotic stress responses. There are limited studies of Soloist genes and their functions are poorly understood. We characterized the abiotic and biotic stress tolerance function of the ScSoloist gene (designated as ScAPD1-like) from the desert moss Syntrichia caninervis. ScAPD1-like responded to multiple abiotic, biotic stresses and plant hormone treatments. ScAPD1-like protein located to the nucleus and bound to several DNA elements. Overexpression of ScAPD1-like in Arabidopsis did not alter abiotic stress resistance or inhibit Pseudomonas syringae pv. tomato (Pst) DC3000 infection. However, overexpression of ScAPD1-like significantly increased the resistance of transgenic Arabidopsis and S. caninervis to Verticillium dahliae infection, decreased reactive oxygen species accumulation and improved reactive oxygen species scavenging activity. ScAPD1-like overexpression plants altered the abundance of transcripts for lignin synthesis and promoted lignin accumulation in Arabidopsis. ScAPD1-like directly bind to RAV1, AC elements, and TATA-box in the promoters of AtPAL1 and AtC4H genes, respectively, in vitro. Chromatin immunoprecipitation-quantitative polymerase chain reaction assays demonstrated ScAPD1-like directly bound to PAL and C4H genes promoters in Arabidopsis and their homologs in S. caninervis. In S. caninervis, ScAPD1-like overexpression and RNAi directly regulated the abundance of ScPAL and ScC4H transcripts and modified the metabolites of phenylpropanoid pathway. We provide insight into the function of Soloist in plant defense mechanisms that likely occurs through activation of the phenylpropanoid biosynthesis pathway. ScAPD1-like is a promising candidate gene for breeding strategies to improve resistance to Verticillium wilt.

Multicopper oxidases GbAO and GbSKS are involved in the Verticillium dahliae resistance in Gossypium barbadense

Ascorbate oxidase (AO) and skewed5 (SKU5)-similar (SKS) proteins belong to the multicopper oxidase (MCO) family and play important roles in plants in response to environmental stress via modulation of oxidoreduction homeostasis. Currently, reports on the response of Gossypium barbadense MCO to Verticillium wilt (VW) caused by Verticillium dahliae are still limited. Herein, RNA sequencing of two G. barbadense cultivars of VW-resistant XH21 and VW-susceptible XH7 under V. dahliae treatment, combined with physiological and genetic analysis, was performed to analyze the function and mechanism of multicopper oxidases GbAO and GbSKS involved in V. dahliae resistance. The identified differentially expressed genes are mainly involved in the regulation of oxidoreduction reaction, and extracellular components and signaling. Interestingly, ascorbate oxidase family members were discovered as the most significantly upregulated genes after V. dahliae treatment, including GbAO3A/D, GbSKS3A/D, and GbSKS16A/D. H₂O₂ and Asc contents, especially reductive Asc in both XH21 and XH7, were shown to be increased. Silenced expression of respective GbAO3A/D, GbSKS3A/D, and GbSKS16A/D in virus-induced gene silencing (VIGS) cotton plants significantly decreased the resistance to V. dahliae, coupled with the reduced contents of pectin and lignin. Our results indicate that AO might be involved in cotton VW resistance via the regulation of cell wall components.