Regulation and integration of plant jasmonate signaling: a comparative view of monocot and dicot

The MdNAC72-MdABI5 module acts as an interface integrating jasmonic acid and gibberellin signals and undergoes ubiquitination-dependent degradation regulated by MdSINA2 in apple

Jasmonic acid (JA) and gibberellin (GA) coordinately regulate plant developmental programs and environmental cue responses. However, the fine regulatory network of the cross-interaction between JA and GA remains largely elusive. In this study, we demonstrate that MdNAC72 together with MdABI5 positively regulates anthocyanin biosynthesis through an exquisite MdNAC72-MdABI5-MdbHLH3 transcriptional cascade in apple. MdNAC72 interacts with MdABI5 to promote the transcriptional activation of MdABI5 on its target gene MdbHLH3 and directly activates the transcription of MdABI5. The MdNAC72-MdABI5 module regulates the integration of JA and GA signals in anthocyanin biosynthesis by combining with JA repressor MdJAZ2 and GA repressor MdRGL2a. MdJAZ2 disrupts the MdNAC72-MdABI5 interaction and attenuates the transcriptional activation of MdABI5 by MdNAC72. MdRGL2a sequesters MdJAZ2 from the MdJAZ2-MdNAC72 protein complex, leading to the release of MdNAC72. The E3 ubiquitin ligase MdSINA2 is responsive to JA and GA signals and promotes ubiquitination-dependent degradation of MdNAC72. The MdNAC72-MdABI5 interface fine-regulates the integration of JA and GA signals at the transcriptional and posttranslational levels by combining MdJAZ2, MdRGL2a, and MdSINA2. In summary, our findings elucidate the fine regulatory network connecting JA and GA signals with MdNAC72-MdABI5 as the core in apple.

OsGELP77, a QTL for broad-spectrum disease resistance and yield in rice, encodes a GDSL-type lipase

Lipids and lipid metabolites have essential roles in plant-pathogen interactions. GDSL-type lipases are involved in lipid metabolism modulating lipid homeostasis. Some plant GDSLs modulate lipid metabolism altering hormone signal transduction to regulate host-defence immunity. Here, we functionally characterized a rice lipase, OsGELP77, promoting both immunity and yield. OsGELP77 expression was induced by pathogen infection and jasmonic acid (JA) treatment. Overexpression of OsGELP77 enhanced rice resistance to both bacterial and fungal pathogens, while loss-of-function of osgelp77 showed susceptibility. OsGELP77 localizes to endoplasmic reticulum and is a functional lipase hydrolysing universal lipid substrates. Lipidomics analyses demonstrate that OsGELP77 is crucial for lipid metabolism and lipid-derived JA homeostasis. Genetic analyses confirm that OsGELP77-modulated resistance depends on JA signal transduction. Moreover, population genetic analyses indicate that OsGELP77 expression level is positively correlated with rice resistance against pathogens. Three haplotypes were classified based on nucleotide polymorphisms in the OsGELP77 promoter where OsGELP77Hap3 is an elite haplotype. Three OsGELP77 haplotypes are differentially distributed in wild and cultivated rice, while OsGELP77Hap3 has been broadly pyramided for hybrid rice development. Furthermore, quantitative trait locus (QTL) mapping and resistance evaluation of the constructed near-isogenic line validated OsGELP77, a QTL for broad-spectrum disease resistance. In addition, OsGELP77-modulated lipid metabolism promotes JA accumulation facilitating grain yield. Notably, the hub defence regulator OsWRKY45 acts upstream of OsGELP77 by initiating the JA-dependent signalling to trigger immunity. Together, OsGELP77, a QTL contributing to immunity and yield, is a candidate for breeding broad-spectrum resistant and high-yielding rice.

A Roadmap from Functional Materials to Plant Health Monitoring (PHM)

Soft bioelectronics have great potential for the early diagnosis of plant diseases and the mitigation of adverse outcomes such as reduced crop yields and stunted growth. Over the past decade, bioelectronic interfaces have evolved into miniaturized conformal electronic devices that integrate flexible monitoring systems with advanced electronic functionality. This development is largely attributable to advances in materials science, and micro/nanofabrication technology. The approach uses the mechanical and electronic properties of functional materials (polymer substrates and sensing elements) to create interfaces for plant monitoring. In addition to ensuring biocompatibility, several other factors need to be considered when developing these interfaces. These include the choice of materials, fabrication techniques, precision, electrical performance, and mechanical stability. In this review, some of the benefits plants can derive from several of the materials used to develop soft bioelectronic interfaces are discussed. The article describes how they can be used to create biocompatible monitoring devices that can enhance plant growth and health. Evaluation of these devices also takes into account features that ensure their long-term durability, sensitivity, and reliability. This article concludes with a discussion of the development of reliable soft bioelectronic systems for plants, which has the potential to advance the field of bioelectronics.

Molecular mechanism of salinity and waterlogging tolerance in mangrove Kandelia obovata

Mangrove forests are colloquially referred to as "Earth's kidneys" and serve many important ecological and commercial functions. Salinity and waterlogging stress are the most important abiotic stressors restricting the growth and development of mangroves. Kandelia obovata (K. obovata) is the greatest latitudinally-distributed salt mangrove species in China.Here, morphology and transcriptomics were used to study the response of K. obovata to salt and waterlogging stress. In addition, weighted gene co-expression network analysis of the combined gene expression and phenotypic datasets was used to identify core salinity- and waterlogging-responsive modules. In this study, we observed that both high salinity and waterlogging significantly inhibited growth and development in K. obovata. Notably, growth was negatively correlated with salt concentration and positively correlated with waterlogging duration, and high salinity was significantly more inhibitive than waterlogging. A total of 7, 591 salt-responsive and 228 waterlogging-responsive differentially expressed genes were identified by RNA sequencing. Long-term salt stress was highly correlated with the measured physiological parameters while long-term waterlogging was poorly correlated with these traits. At the same time, 45 salinity-responsive and 16 waterlogging-responsive core genes were identified. All 61 core genes were mainly involved in metabolic and biosynthesis of secondary metabolites pathways. This study provides valuable insight into the molecular mechanisms of salinity and waterlogging tolerance in K. obovata, as well as a useful genetic resource for the improvement of mangrove stress tolerance using molecular breeding techniques.

Rice tetraspanins express in specific domains of diverse tissues and regulate plant architecture and root growth

Tetraspanins (TETs) are small transmembrane scaffold proteins that distribute proteins into highly organized microdomains, consisting of adaptors and signaling proteins, which play important roles in various biological events. In plants, understanding of tetraspanin is limited to the Arabidopsis TET genes' expression pattern and their function in leaf and root growth. Here, we comprehensively analyzed all rice tetraspanin (OsTET) family members, including their gene expression pattern, protein topology, and subcellular localization. We found that the core domain of OsTETs is conserved and shares a similar topology of four membrane-spanning domains with animal and plant TETs. OsTET genes are partially overlapping expressed in diverse tissue domains in vegetative and reproductive organs. OsTET proteins preferentially targeted the endoplasmic reticulum. Mutation analysis showed that OsTET5, OsTET6, OsTET9, and OsTET10 regulated plant height and tillering, and that OsTET13 controlled root growth in association with the jasmonic acid pathway. In summary, our work provides systematic new insights into the function of OsTETs in rice growth and development, and the data provides valuable resources for future research.

Jasmonate: A Hormone of Primary Importance for Temperature Stress Response in Plants

Temperature is a critical environmental factor that plays a vital role in plant growth and development. Temperatures below or above the optimum ranges lead to cold or heat stress, respectively. Temperature stress retards plant growth and development, and it reduces crop yields. Jasmonates (JAs) are a class of oxylipin phytohormones that play various roles in growth, development, and stress response. In recent years, studies have demonstrated that cold and heat stress affect JA biosynthesis and signaling, and JA plays an important role in the response to temperature stress. Recent studies have provided a large body of information elucidating the mechanisms underlying JA-mediated temperature stress response. In the present review, we present recent advances in understanding the role of JA in the response to cold and heat stress, and how JA interacts with other phytohormones during this process.

Jasmonates and salicylic acid as enigmatic orchestrators of capitula senescence in Cosmos sulphureus Cav

The fine-tuning of the intricate network of plant growth hormones empowers the balanced responses of plants to environmental and developmental signals. Salicylic acid and jasmonates are emerging as advanced hormones that provide plants with resistance to environmental stresses. Senescence is characterized by coordinated and systematic crosstalk between phytohormones that remodels the biochemical and physiological mechanisms in plants, resulting in cell death. The present investigation examines the role of jasmonates (methyl jasmonate and jasmonic acid) and salicylic acid (SA) in regulating the petal senescence of detached stalks of Cosmos sulphureus. Based on our results, it was revealed that SA and jasmonic acid (JA) at 40 μM and methyl jasmonate (MJ) at 0.75 μM concentration delayed the senescence of detached flowers of C. sulphureus considerably. These growth regulators improved the membrane stability, reinforced the antioxidant enzyme activities and averted the upsurge of hydrogen peroxide (H2O2) content in the petals. Additionally, SA and jasmonates preserved higher content of total phenols, reducing sugars and soluble proteins in the petals, besides impeding the bacterial growth in testing solutions which corroborated with the maximum solution uptake. The elevated soluble protein content was found to be associated with low specific protease activity (SPA) and α-amino acid content in the petal tissues. Our study concluded that SA and jasmonates delayed flower senescence by averting oxidative stress and maintaining the nutritional status of the petals.

Large-scale phosphoproteome analysis in wheat seedling leaves provides evidence for extensive phosphorylation of regulatory proteins during CWMV infection

BACKGROUND

Chinese wheat mosaic virus (CWMV) often causes severe damage to wheat (Triticum aestivum L.) growth and yield. It is well known that a successful infection in plants depends on a complex interaction between the host plant and the pathogen. Post-translational modification (PTM) of proteins is considered to be one of the main processes that decides the outcome of the plant-pathogen arms race during this interaction. Although numerous studies have investigated PTM in various organisms, there has been no large-scale phosphoproteomic analysis of virus-infected wheat plants. We therefore aimed to investigate the CWMV infection-induced phosphoproteomics changes in wheat by high-resolution liquid chromatography-tandem mass spectroscopy (LC-MS/MS) using affinity-enriched peptides followed by comprehensive bioinformatics analysis.

RESULTS

Through this study, a total of 4095 phosphorylation sites have been identified in 1968 proteins, and 11.6% of the phosphorylated proteins exhibited significant changes (PSPCs) in their phosphorylation levels upon CWMV infection. The result of Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis showed that most of the PSPCs were associated with photosynthesis, plant-pathogen interactions, and MAPK signaling pathways. The protein-protein interaction (PPI) network analysis result showed that these PSPCs were mainly participated in the regulation of biosynthesis and metabolism, protein kinase activities, and transcription factors. Furthermore, the phosphorylation levels of TaChi1 and TaP5CS, two plant immunity-related enzymes, were significantly changed upon CWMV infection, resulting in a significant decrease in CWMV accumulation in the infected plants.

CONCLUSIONS

Our results indicate that phosphorylation modification of protein plays a critical role in wheat resistance to CWMV infection. Upon CWMV infection, wheat plants will regulate the levels of extra- and intra-cellular signals and modifications of enzyme activities via protein phosphorylation. This novel information about the strategies used by wheat to resist CWMV infection will help researchers to breed new CWMV-resistant cultivars and to better understand the arms race between wheat and CWMV.

Poaceae-specific β-1,3;1,4-d-glucans link jasmonate signalling to OsLecRK1-mediated defence response during rice-brown planthopper interactions

Brown planthopper (BPH, Nilaparvata lugens), a highly destructive insect pest, poses a serious threat to rice (Oryza sativa) production worldwide. Jasmonates are key phytohormones that regulate plant defences against BPH; however, the molecular link between jasmonates and BPH responses in rice remains largely unknown. Here, we discovered a Poaceae-specific metabolite, mixed-linkage β-1,3;1,4-d-glucan (MLG), which contributes to jasmonate-mediated BPH resistance. MLG levels in rice significantly increased upon BPH attack. Overexpressing OsCslF6, which encodes a glucan synthase that catalyses MLG biosynthesis, significantly enhanced BPH resistance and cell wall thickness in vascular bundles, whereas knockout of OsCslF6 reduced BPH resistance and vascular wall thickness. OsMYC2, a master transcription factor of jasmonate signalling, directly controlled the upregulation of OsCslF6 in response to BPH feeding. The AT-rich domain of the OsCslF6 promoter varies in rice varieties from different locations and natural variants in this domain were associated with BPH resistance. MLG-derived oligosaccharides bound to the plasma membrane-anchored LECTIN RECEPTOR KINASE1 OsLecRK1 and modulated its activity. Thus, our findings suggest that the OsMYC2-OsCslF6 module regulates pest resistance by modulating MLG production to enhance vascular wall thickness and OsLecRK1-mediated defence signalling during rice-BPH interactions.

The MYB59 transcription factor negatively regulates salicylic acid- and jasmonic acid-mediated leaf senescence

Leaf senescence is the final stage of leaf development and is affected by various exogenous and endogenous factors. Transcriptional regulation is essential for leaf senescence, however, the underlying molecular mechanisms remain largely unclear. In this study, we report that the transcription factor MYB59, which was predominantly expressed in early senescent rosette leaves, negatively regulates leaf senescence in Arabidopsis (Arabidopsis thaliana). RNA sequencing revealed a large number of differentially expressed genes involved in several senescence-related biological processes in myb59-1 rosette leaves. Chromatin immunoprecipitation and transient dual-luciferase reporter assays demonstrated that MYB59 directly repressed the expression of SENESCENCE ASSOCIATED GENE 18 and indirectly inhibited the expression of several other senescence-associated genes to delay leaf senescence. Moreover, MYB59 was induced by salicylic acid (SA) and jasmonic acid (JA). MYB59 inhibited SA production by directly repressing the expression of ISOCHORISMATE SYNTHASE 1 and PHENYLALANINE AMMONIA-LYASE 2 and restrained JA biosynthesis by directly suppressing the expression of LIPOXYGENASE 2, thus forming two negative feedback regulatory loops with SA and JA and ultimately delaying leaf senescence. These results help us understand the novel function of MYB59 and provide insights into the regulatory network controlling leaf senescence in Arabidopsis.

Multi-stress resilience in plants recovering from submergence

Submergence limits plants' access to oxygen and light, causing massive changes in metabolism; after submergence, plants experience additional stresses, including reoxygenation, dehydration, photoinhibition and accelerated senescence. Plant responses to waterlogging and partial or complete submergence have been well studied, but our understanding of plant responses during post-submergence recovery remains limited. During post-submergence recovery, whether a plant can repair the damage caused by submergence and reoxygenation and re-activate key processes to continue to grow, determines whether the plant survives. Here, we summarize the challenges plants face when recovering from submergence, primarily focusing on studies of Arabidopsis thaliana and rice (Oryza sativa). We also highlight recent progress in elucidating the interplay among various regulatory pathways, compare post-hypoxia reoxygenation between plants and animals and provide new perspectives for future studies.

Jasmonate Positively Regulates Cold Tolerance by Promoting ABA Biosynthesis in Tomato

As a cold-sensitive species, tomato is frequently challenged by cold stress during vegetative and reproductive growth. Understanding how tomato responds to cold stress is of critical importance for sustainable tomato production. In this work, we demonstrate that jasmonate (JA) plays a crucial role in tomato response to cold stress by promoting abscisic acid (ABA) biosynthesis. It was observed that both JA and ABA levels were substantially increased under cold conditions, whereas the suppression of JA biosynthesis abated ABA accumulation. The ABA biosynthesis gene 9-CIS-EPOXYCAROTENOID DIOXYGENASE2 (NCED2) was subsequently found to be associated with JA-mediated ABA biosynthesis in tomato plants in response to cold stress. NCED2 was rapidly induced by exogenous MeJA and cold treatment. Silencing NCED2 led to a decrease in ABA accumulation that was concurrent with increased cold sensitivity. Moreover, blocking ABA biosynthesis using a chemical inhibitor impaired JA-induced cold tolerance in tomato. Furthermore, MYC2, a core component of the JA signaling pathway, promoted the transcription of NCED2, ABA accumulation and cold tolerance in tomato. Collectively, our results support that JA signaling promotes ABA biosynthesis to confer cold tolerance in tomato.

Transcriptomic analysis reveals the formation mechanism of anemone-type flower in chrysanthemum

BACKGROUND

The ray and disc florets on the chrysanthemum capitulum are morphologically diverse and have remarkably abundant variant types, resulting in a rich variety of flower types. An anemone shape with pigmented and elongated disk florets is an important trait in flower shape breeding of chrysanthemums. The regulatory mechanism of their anemone-type disc floret formation was not clear, thus limiting the directional breeding of chrysanthemum flower types. In this study, we used morphological observation, transcriptomic analysis, and gene expression to investigate the morphogenetic processes and regulatory mechanisms of anemone-type chrysanthemum.

RESULT

Scanning electron microscopy (SEM) observation showed that morphological differences between non-anemone-type disc florets and anemone-type disc florets occurred mainly during the petal elongation period. The anemone-type disc florets elongated rapidly in the later stages of development. Longitudinal paraffin section analysis revealed that the anemone-type disc florets were formed by a great number of cells in the middle layer of the petals with vigorous division. We investigated the differentially expressed genes (DEGs) using ray and disc florets of two chrysanthemum cultivars, 082 and 068, for RNA-Seq and their expression patterns of non-anemone-type and anemone-type disc florets. The result suggested that the CYCLOIDEA2 (CYC2s), MADS-box genes, and phytohormone signal-related genes appeared significantly different in both types of disc florets and might have important effects on the formation of anemone-type disc florets. In addition, it is noteworthy that the auxin and jasmonate signaling pathways might play a vital role in developing anemone-type disc florets.

CONCLUSIONS

Based on our findings, we propose a regulatory network for forming non-anemone-type and anemone-type disc florets. The results of this study lead the way to further clarify the mechanism of the anemone-type chrysanthemum formation and lay the foundation for the directive breeding of chrysanthemum petal types.

The involvement of the phenylpropanoid and jasmonate pathways in methyl jasmonate-induced soft rot resistance in kiwifruit (Actinidia chinensis)

Botryosphaeria dothidea is a major postharvest causal agent of soft rot in kiwifruit. Methyl jasmonate (MeJA) is an important plant hormone that participates as a plant defense against pathogens from a signal molecule. However, the impact and regulatory mechanism of MeJA on the attenuation of kiwifruit fungal decay remains unknown. This work investigated the effects of exogenous MeJA on the enzyme activity, metabolite content and gene expression of the phenylpropanoid and jasmonate pathways in kiwifruit. The results revealed that MeJA inhibited the expansion of B. dothidea lesion diameter in kiwifruit (Actinidia chinensis cv. 'Hongyang'), enhanced the activity of enzymes (phenylalanine ammonia lyase, cinnamate 4-hydroxylase, 4-coumarate: coenzyme A ligase, cinnamyl alcohol dehydrogenase, peroxidase and polyphenol oxidase), and upregulated the expression of related genes (AcPAL, AcC4H, Ac4CL, and AcCAD). The accumulation of metabolites (total phenolics, flavonoids, chlorogenic acid, caffeic acid and lignin) with inhibitory effects on pathogens was promoted. Moreover, MeJA enhanced the expression of AcLOX, AcAOS, AcAOC, AcOPR3, AcJAR1, AcCOI1 and AcMYC2 and reduced the expression of AcJAZ. These results suggest that MeJA could display a better performance in enhancing the resistance of disease in kiwifruit by regulating the phenylpropanoid pathway and jasmonate pathway.

Direct toxicity of the herbicide florasulam against Chlorella vulgaris: An integrated physiological and metabolomic analysis

Herbicides are the agents of choice for use in weed control; however, they can enter the aquatic environment, with potentially serious consequences for non-target organisms. Despite the possible deleterious effects, little information is available regarding the ecotoxicity of the herbicide florasulam toward aquatic organisms. Accordingly, in this study, we investigated the toxic effect of florasulam on the freshwater microalga Chlorella vulgaris and sought to identify the underlying mechanisms. For this, we employed a growth inhibition toxicity test, and then assessed the changes in physiological and metabolomic parameters, including photosynthetic pigment content, antioxidant system, intracellular structure and complexity, and metabolite levels. The results showed that treatment with florasulam for 96 h at the concentration of 2 mg/L, 2.84 mg/L, and 6 mg/L in medium significantly inhibited algal growth and photosynthetic pigment content. Moreover, the levels of reactive oxygen species were also increased, resulting in oxidative damage and the upregulation of the activities of several antioxidant enzymes. Transmission electron microscopic and flow cytometric analysis further demonstrated that exposure to florasulam (6 mg/L) for 96 h disrupted the cell structure of C. vulgaris, characterized by the loss of cell membrane integrity and alterations in cell morphology. Changes in amino acid metabolism, carbohydrate metabolism, and the antioxidant system were also observed and contributed to the suppressive effect of florasulam on the growth of this microalga. Our findings regarding the potential risks of florasulam in aquatic ecosystems provide a reference for the safe application of this herbicide in the environment.

Ectopic Expression of HbRPW8-a from Hevea brasiliensis Improves Arabidopsis thaliana Resistance to Powdery Mildew Fungi (Erysiphe cichoracearum UCSC1)

The RPW8s (Resistance to Powdery Mildew 8) are atypical broad-spectrum resistance genes that provide resistance to the powdery mildew fungi. Powdery mildew of rubber tree is one of the serious fungal diseases that affect tree growth and latex production. However, the RPW8 homologs in rubber tree and their role of resistance to powdery mildew remain unclear. In this study, four RPW8 genes, HbRPW8-a, b, c, d, were identified in rubber tree, and phylogenetic analysis showed that HbRPW8-a was clustered with AtRPW8.1 and AtRPW8.2 of Arabidopsis. The HbRPW8-a protein was localized on the plasma membrane and its expression in rubber tree was significantly induced upon powdery mildew infection. Transient expression of HbRPW8-a in tobacco leaves induced plant immune responses, including the accumulation of reactive oxygen species and the deposition of callose in plant cells, which was similar to that induced by AtRPW8.2. Consistently, overexpression of HbRPW8-a in Arabidopsis thaliana enhanced plant resistance to Erysiphe cichoracearum UCSC1 and Pseudomonas syringae pv. tomato DC30000 (PstDC3000). Moreover, such HbRPW8-a mediated resistance to powdery mildew was in a salicylic acid (SA) dependent manner. Taken together, we demonstrated a new RPW8 member in rubber tree, HbRPW8-a, which could potentially contribute the resistance to powdery mildew.

Integrative Analysis of Metabolome and Transcriptome Reveals the Role of Strigolactones in Wounding-Induced Rice Metabolic Re-Programming

Plants have evolved mechanisms to adapt to wounding, a threat occurring separately or concomitantly with other stresses. During the last decades, many efforts have been made to elucidate the wounding signaling transduction. However, we know little about the metabolic re-programming under wounding, let alone whether and how strigolactones (SLs) participate in this progress. Here, we reported a metabolomic and transcriptomic analysis of SLs synthetic and signal mutants in rice before and after wounding. A series of metabolites differentially responded to wounding in the SLs mutants and wild-type rice, among which flavones were enriched. Besides, the SLs mutants accumulated more jasmonic acid (JA) and jasmonyl isoleucine (JA-lle) than the wild-type rice after wounding, suggesting an interplay of SLs and JAs during responding to wounding. Further transcriptome data showed that cell wall, ethylene, and flavones pathways might be affected by wounding and SLs. In addition, we identified candidate genes regulated by SLs and responding to wounding. In conclusion, our work provides new insights into wounding-induced metabolic re-programming and the SLs’ function.