A cell wall-localized β-1,3-glucanase promotes fiber cell elongation and secondary cell wall deposition

Inheritance of resilience: genetic Mapping of transgenerational and intergenerational drought stress memory in wheat

Drought stress is a critical challenge for global wheat production, threatening food security by reducing crop yields and quality. The ability of wheat to adapt to and survive under drought conditions is largely dependent on its genetic makeup. Therefore, understanding the genetic associations controlling the effects of intergenerational and transgenerational stress memory underlying drought exposure histories in a diverse collection of 111 wheat accessions using a genome-wide association study (GWAS) plays a significant role in sustaining yields. In this study, we conducted a comprehensive comparison between seeds from the second-generation group that were not subjected to drought stress (C1C2) and seeds from groups that experienced drought stress in one generation, either two generations prior (D1C2; transgenerational drought memory) or in the preceding generation (C1D2; intergenerational drought memory). Additionally, we analyzed seeds from the group exposed to drought stress in both generations (D1D2; combined drought memory). Our findings reveal that historical exposure to drought stress, irrespective of the specific generational context, led to significant alterations in several key plant characteristics, including spike length, the number of spikelets per spike, grain number per spike, grain weight per spike, thousand kernel weight, and levels of both enzymatic and non-enzymatic antioxidants. These results suggest that previous encounters with drought stress impart a lasting impact on the plant, potentially priming it for altered responses under future stress conditions. Using GWAS analysis, we identified highly significant associations and candidate genes associated with most of the traits evaluated, highlighting the genetic underpinnings that may drive these stress memory effects. Interestingly, the candidate gene TraesCS2A02G432800 on chromosome 2 A mapped as Leucine-rich repeat protein 1 (LRR) that harbors the variation of all the agronomical traits for the wheat genotypes that experienced drought stress over three generations. LRR proteins are involved in various physiological processes, including stress response, making them key players in the adaptation of wheat to drought stress. This research underscores the importance of understanding environmental stressors' transgenerational and intergenerational impact on crop performance, with potential implications for breeding and agricultural resilience.

GhMYB102 affects cotton fibre elongation and secondary wall thickening by regulating GhIRX10 in cotton

Upland cotton (Gossypium hirsutum) is a principal economic crop and a fundamental raw material for the textile industry. The quality of cotton fibres is significantly influenced by the synthesis of cell wall polysaccharides. This study focuses on GhIRX10, a beta-1,4-xylosyltransferase crucial for xylan backbone synthesis. Overexpression of GhIRX10 enhances xylan synthesis, which impacts fibre elongation and secondary cell wall thickening. GhMYB102, identified as a direct regulator of GhIRX10 expression, was confirmed through comprehensive validation. Overexpression of GhMYB102 resulted in a similar phenotype as OE-GhIRX10: increased cell wall thickness and reduced fibre length. Overexpression of GhMYB102 upregulated the expression of key cell wall synthesis-related genes, including GhCESA4/7/8, GhIRXs, GhCESAs, GhGUXs, GhTBLs, GhXTHs, and GhXXTs. Consequently, the cellulose and hemicellulose contents in OE-GhMYB102 lines were significantly increased. GhMYB102 was also validated as a target gene regulated by GhFSN1 and GhMYB7, with the ability to reciprocally regulate GhFSN1 expression. In summary, we propose a regulatory model where GhMYB102 promotes the expression of GhIRX10 and other cell wall-related genes, thereby affecting fibre quality. This study elucidates the regulatory network of secondary cell wall synthesis in cotton and provides potential targets for improving fibre quality through molecular breeding.

Modulation of morphogenesis and metabolism by plant cell biomechanics: from model plants to traditional herbs

The quality of traditional herbs depends on organ morphogenesis and the accumulation of active pharmaceutical ingredients. While recent research highlights the significance of cell mechanobiology in model plant morphogenesis, our understanding of mechanical signal initiation and transduction in traditional herbs remains incomplete. Recent studies reveal a close correlation between cell wall (CW) biosynthesis and active ingredient production, yet the role of cell mechanics in balancing morphogenesis and secondary metabolism is often overlooked. This review explores how the cell wall, plasma membrane, cytoskeleton, and vacuole collaborate to regulate cell mechanics and respond to mechanical changes. We propose CW biosynthesis as a hub in connecting cell mechanics with secondary metabolism and emphasize that understanding the relationship between mechanical remodeling and secondary metabolism could provide new insights into plant cell mechanobiology and the breeding of high-quality herbs.

Genome-wide analysis of Class III peroxidase (PRX) family core genes and functional mechanism of GhPRXR1-A for seed development in Gossypium hirsutum

Class III peroxidases (PRXs) play critical roles in plant growth and development by oxidizing various substrates with H2O2. Although many PRXs have been identified and their roles in biotic and abiotic stress responses have extensively investigated in plants. However, functional mechanisms of PRXs in seed development remain poorly understood. In this study, 14, 17, 9, and 13 PRX core genes were identified in Gossypium hirsutum, Gossypium barbadense, Gossypium arboreum, and Gossypium raimondii, respectively. Phylogenetic analysis categorized PRXs core genes of cotton into five groups. Six of the GhPRX genes co-localized with quantitative trait loci (QTLs) associated with oil or seed size, and GhPRXR1-A showed significant high expression levels in developing ovules. Heterologous overexpression of GhPRXR1-A in Arabidopsis thaliana resulted in a significant increase in thousand seed weight (Col-0: 0.015 ± 0.00085 g vs. OE-GhPRXR1-A: 0.022 ± 0.0019 g). In addition, molecular mechanism assays revealed that GhPRXR1-A is directly activated by GhGATA1 and interacts with GhNFYC4, a transcription factor of the nuclear factor Y, C subunit family that has previously been reported to mediate seed development. Collectively, these findings suggest that GhPRXR1-A is a regulator of seed development in Arabidopsis and may have similar functional role in cotton seed contributing traits.

COBRA-LIKE 9 modulates cotton cell wall development via regulating cellulose deposition

Plant cell walls are complex and dynamic cellular structures critical for plant growth, development, physiology, and adaptation. Cellulose is one of the most important components of the cell wall. However, how cellulose microfibrils deposit and assemble into crystalline cellulose remains elusive. The COBRA-LIKE plant-specific protein family plays a vital role in modulating the deposition and orientation of cellulose microfibril in plant cell walls. Here, we investigate the role of GhCOBL9 in cotton (Gossypium hirsutum) fiber development, an ideal model for studying cell elongation and cell wall thickening. The expression period of GhCOBL9 is consistent with the thickening stage of the secondary wall of cotton fibers. Overexpression of GhCOBL9 results in increased cellulose content in the cell wall and produces shorter, thicker, and stronger fibers, while RNA interference (RNAi)-mediated downregulation of GhCOBL9 leads to the opposite phenotypes, indicating its crucial role in cell wall development. Subcellular localization and binding activity assays reveal that GhCOBL9 targets the cell wall and binds to crystalline cellulose with high affinity. Transcriptomic analysis of GhCOBL9 transgenic lines uncovers expression alterations in genes related to cellulose and monosaccharide biosynthesis. Furthermore, we identify a fasciclin-like arabinogalactan protein 9 (GhFLA9) as an interacting partner of GhCOBL9 to modulate cell wall development. Additionally, the R2R3-MYB transcription factor GhMYB46-5 activates GhCOBL9 expression by binding to the MYB46-responsive cis-regulatory element in the GhCOBL9 promoter. These findings broaden our knowledge of COBL function in modulating plant cell wall development.

A single-nucleotide polymorphism in PvPW1 encoding β-1,3-glucanase 9 is associated with pod width in Phaseolus vulgaris L

Pod width influences pod size, shape, yield, and consumer preference in snap beans (Phaseolus vulgaris L.). In this study, we map PvPW1, a quantitative trait locus associated with pod width in snap beans, through genotyping and phenotyping of recombinant plants. We identify Phvul.006G072800, encoding the β-1,3-glucanase 9 protein, as the causal gene for PvPW1. The PvPW1G3555 allele is found to positively regulate pod width, as revealed by an association analysis between pod width phenotype and the PvPW1G3555C genotype across 17 bi-parental F2 populations. In total, 97.7% of the 133 wide pod accessions carry PvPW1G3555, while 82.1% of the 78 narrow pod accessions carry PvPW1C3555, indicating strong selection pressure on PvPW1 during common bean breeding. Re-sequencing data from 59 common bean cultivars identify an 8-bp deletion in the intron linked to PvPW1C3555, leading to the development of the InDel marker of PvM436. Genotyping 317 common bean accessions with PvM436 demonstrated that accessions with PvM436247 and PvM436227 alleles have wider pods compared to those with PvM436219 allele, establishing PvM436 as a reliable marker for molecular breeding in snap beans. These findings highlight PvPW1 as a critical gene regulating pod width and underscore the utility of PvM436 in marker-assisted selection for snap bean breeding.

Daily glycome and transcriptome profiling reveals polysaccharide structures and correlated glycosyltransferases critical for cotton fiber growth

Cotton fiber is the most valuable naturally available material for the textile industry and the fiber length and strength are key determinants of its quality. Dynamic changes in the pectin, xyloglucan, xylan, and cellulose polysaccharide epitope content during fiber growth contribute to complex remodeling of fiber cell wall (CW) and quality. Detailed knowledge about polysaccharide compositional and structural alteration in the fiber during fiber elongation and strengthening is important to understand the molecular dynamics of fiber development and improve its quality. Here, large-scale glycome profiling coupled with fiber phenotype and transcriptome profiling was conducted on fiber collected daily covering the most critical window of fiber development. The profiling studies with high temporal resolution allowed us to identify specific polysaccharide epitopes associated with distinct fiber phenotypes that might contribute to fiber quality. This study revealed the critical role of highly branched RG-I pectin epitopes such as β-1,4-linked-galactans, β-1,6-linked-galactans, and arabinogalactans, in addition to earlier reported homogalacturonans and xyloglucans in the formation of cotton fiber middle lamella and contributing to fiber plasticity and elongation. We also propose the essential role of heteroxylans (Xyl-MeGlcA and Xyl-3Ar), as a guiding factor for secondary CW cellulose microfibril arrangement, thus contributing to fiber strength. Correlation analysis of profiles of polysaccharide epitopes from glycome data and expression profiles of glycosyltransferase-encoding genes from transcriptome data identified several key putative glycosyltransferases that are potentially involved in synthesizing the critical polysaccharide epitopes. The findings of this study provide a foundation to identify molecular factors that dictate important fiber traits.

Arabidopsis PDLP7 modulated plasmodesmata function is related to BG10-dependent glucosidase activity required for callose degradation

The microdomains of plasmodesmata, specialized cell-wall channels responsible for communications between neighboring cells, are composed of various plasmodesmata-located proteins (PDLPs) and lipids. Here, we found that, among all PDLP or homologous proteins in Arabidopsis thaliana genome, PDLP5 and PDLP7 possessed a C-terminal sphingolipid-binding motif, with the latter being the only member that was significantly upregulated upon turnip mosaic virus and cucumber mosaic virus infections. pdlp7 mutant plants exhibited significantly reduced callose deposition, larger plasmodesmata diameters, and faster viral transmission. These plants exhibited increased glucosidase activity but no change in callose synthase activity. PDLP7 interacted specifically with glucan endo-1,3-β-glucosidase 10 (BG10). Consistently, higher levels of callose deposition and slower virus transmission in bg10 mutants were observed. The interaction between PDLP7 and BG10 was found to depend on the presence of the Gnk2-homologous 1 (GnK2-1) domain at the N terminus of PDLP7 with Asp-35, Cys-42, Gln-44, and Leu-116 being essential. In vitro supplementation of callose was able to change the conformation of the GnK2-1 domain. Our data suggest that the GnK2-1 domain of PDLP7, in conjunction with callose and BG10, plays a key role in plasmodesmata opening and closure, which is necessary for intercellular movement of various molecules.

Genome-wide identification of the grapevine β-1,3-glucanase gene (VviBG) family and expression analysis under different stresses

BACKGROUND

The β-1,3-glucanase gene is widely involved in plant development and stress defense. However, an identification and expression analysis of the grape β-1,3-glucanase gene (VviBG) family had not been conducted prior to this study.

RESULTS

Here, 42 VviBGs were identified in grapevine, all of which contain a GH-17 domain and a variable C-terminal domain. VviBGs were divided into three clades α, β and γ, and six subgroups A-F, with relatively conserved motifs/domains and intron/exon structures within each subgroup. The VviBG gene family contained four tandem repeat gene clusters. There were intra-species synteny relationships between two pairs of VviBGs and inter-species synteny relationships between 20 pairs of VviBGs and AtBGs. The VviBG promoter contained many cis-acting elements related to stress and hormone responses. Tissue-specific analysis showed that VviBGs exhibited distinct spatial and temporal expression patterns. Transcriptome analysis indicated that many VviBGs were induced by wounds, UV, downy mildew, cold, salt and drought, especially eight VviBGs in subgroup A of the γ clade. RT-qPCR analysis showed that these eight VviBGs were induced under abiotic stress (except for VviBG41 under cold stress), and most of them were induced at higher expression levels by PEG6000 and NaCl than under cold treatment.

CONCLUSIONS

The chromosome localization, synteny and phylogenetic analysis of the VviBG members were first conducted. The cis-acting elements, transcriptome data and RT-qPCR analysis showed that VviBG genes play a crucial role in grape growth and stress (hormone, biotic and abiotic) responses. Our study laid a foundation for understanding their functions in grape resistance to different stresses.

Deciphering the dynamic expression network of fiber elongation and the functional role of the GhTUB5 gene for fiber length in cotton based on an introgression population of upland cotton

INTRODUCTION

Interspecific introgression between Gossypium hirsutum and G. barbadense allows breeding cotton with outstanding fiber length (FL). However, the dynamic gene regulatory network of FL-related genes has not been characterized, and the functional mechanism through which the hub gene GhTUB5 mediates fiber elongation has yet to be determined.

METHODS

Coexpression analyses of 277 developing fiber transcriptomes integrated with QTL mapping using 250 introgression lines of different FL phenotypes were conducted to identify genes related to fiber elongation. The function of GhTUB5 was determined by ectopic expression of two TUB5 alleles in Arabidopsis and knockout of GhTUB5 in upland cotton. Yeast two-hybrid, split-luciferase and pull-down assays were conducted to screen for interacting proteins, and upstream genes were identified by yeast one-hybrid, dual-LUC and electrophoretic mobility shift assays.

RESULTS

The 32,612, 30,837 and 30,277 genes expressed at 5, 10 and 15 days postanthesis (dpa) were grouped into 19 distinct coexpression modules, and 988 genes in the MEblack module were enriched in the cell wall process and exhibited significant associations with FL. A total of 20 FL-QTLs were identified, each explaining 3.34-16.04 % of the phenotypic variance in the FL. Furthermore, several FL-QTLs contained 15 genes that were differentially expressed in the MEblack module including the tubulin beta gene (TUB5). Compared with the wild type, the overexpression of GhTUB5 and GbTUB5 in Arabidopsis suppressed root cell length but promoted cellulose synthesis. Knockout of GhTUB5 resulted in longer fiber lines. Protein-based experiments revealed that GhTUB5 interacts with GhZFP6. Additionally, GhTUB5 was directly activated by GhHD-ZIP7, a homeobox-leucine zipper transcription factor, and its paralogous gene was previously reported to mediate fiber elongation.

CONCLUSION

This study opens a new avenue to dissect functional mechanism of cotton fiber elongation. Our findings provide some molecular details on how GhTUB5 mediates the FL phenotype in cotton.

Counteracting Grey Mould (Botrytis cinerea) in Grapevine 'Glera' Using Three Putative Biological Control Agent Strains (Paraburkholderia sp., Pseudomonas sp., and Acinetobacter sp.): Impact on Symptoms, Yield, and Gene Expression

This study examined the potential use of three bacterial strains-Paraburkholderia sp. strain CRV74, Pseudomonas sp. strain CRV21, and Acinetobacter sp. strain CRV19-as biocontrol agents of Botrytis cinerea in grapevine. These strains were selected for their ability to inhibit B. cinerea growth in vitro and used in field conditions for the control of grey mould symptoms in 'Glera' grapes. To this end, after inoculating these microorganisms onto plants sprayed with B. cinerea spores, the final yield, the physicochemical characteristics of the must, disease incidence, and the possible influence on the expression of plant-defence proteins were evaluated. Strain CRV21 resulted as being the most effective in combating grey mould (-20% of disease incidence). Although yield was not affected, significantly different values of total soluble solids content was observed. Additionally, a significant up-regulation of the genes PR-1, PR-5, β-1,3-glucanase, and class III chitinase was observed. These findings highlight the potential application of strains with anti-botrytis activity as sustainable alternatives to chemical defence for the control of this pathogen.

Unraveling the lncRNA-miRNA-mRNA Regulatory Network Involved in Poplar Coma Development through High-Throughput Sequencing

Poplar coma, the fluff-like appendages of seeds originating from the differentiated surface cells of the placenta and funicle, aids in the long-distance dispersal of seeds in the spring. However, it also poses hazards to human safety and causes pollution in the surrounding environment. Unraveling the regulatory mechanisms governing the initiation and development of coma is essential for addressing this issue comprehensively. In this study, strand-specific RNA-seq was conducted at three distinct stages of coma development, revealing 1888 lncRNAs and 52,810 mRNAs. The expression profiles of lncRNAs and mRNAs during coma development were analyzed. Subsequently, potential target genes of lncRNAs were predicted through co-localization and co-expression analyses. Integrating various types of sequencing data, lncRNA-miRNA-TF regulatory networks related to the initiation of coma were constructed. Utilizing identified differentially expressed genes encoding kinesin and actin, lncRNA-miRNA-mRNA regulatory networks associated with the construction and arrangement of the coma cytoskeleton were established. Additionally, relying on differentially expressed genes encoding cellulose synthase, sucrose synthase, and expansin, lncRNA-miRNA-mRNA regulatory networks related to coma cell wall synthesis and remodeling were developed. This study not only enhances the comprehension of lncRNA but also provides novel insights into the molecular mechanisms governing the initiation and development of poplar coma.

Genome-Wide Identification of TLP Gene Family in Populus trichocarpa and Functional Characterization of PtTLP6, Preferentially Expressed in Phloem

Thaumatin-like proteins (TLPs) in plants are involved in diverse biotic and abiotic stresses, including antifungal activity, low temperature, drought, and high salinity. However, the roles of the TLP genes are rarely reported in early flowering. Here, the TLP gene family was identified in P. trichocarpa. The 49 PtTLP genes were classified into 10 clusters, and gene structures, conserved motifs, and expression patterns were analyzed in these PtTLP genes. Among 49 PtTLP genes, the PtTLP6 transcription level is preferentially high in stems, and GUS staining signals were mainly detected in the phloem tissues of the PtTLP6pro::GUS transgenic poplars. We generated transgenic Arabidopsis plants overexpressing the PtTLP6 gene, and its overexpression lines showed early flowering phenotypes. However, the expression levels of main flowering regulating genes were not significantly altered in these PtTLP6-overexpressing plants. Our data further showed that overexpression of the PtTLP6 gene led to a reactive oxygen species (ROS) burst in Arabidopsis, which might advance the development process of transgenic plants. In addition, subcellular localization of PtTLP6-fused green fluorescent protein (GFP) was in peroxisome, as suggested by tobacco leaf transient transformation. Overall, this work provides a comprehensive analysis of the TLP gene family in Populus and an insight into the role of TLPs in woody plants.

GhMYB30-GhMUR3 affects fiber elongation and secondary wall thickening in cotton

Xyloglucan, an important hemicellulose, plays a crucial role in maintaining cell wall structure and cell elongation. However, the effects of xyloglucan on cotton fiber development are not well understood. GhMUR3 encodes a xyloglucan galactosyltransferase that is essential for xyloglucan synthesis and is highly expressed during fiber elongation. In this study, we report that GhMUR3 participates in cotton fiber development under the regulation of GhMYB30. Overexpression GhMUR3 affects the fiber elongation and cell wall thickening. Transcriptome showed that the expression of genes involved in secondary cell wall synthesis was prematurely activated in OE-MUR3 lines. In addition, GhMYB30 was identified as a key regulator of GhMUR3 by Y1H, Dual-Luc, and electrophoretic mobility shift assay (EMSA) assays. GhMYB30 directly bound the GhMUR3 promoter and activated GhMUR3 expression. Furthermore, DAP-seq of GhMYB30 was performed to identify its target genes in the whole genome. The results showed that many target genes were associated with fiber development, including cell wall synthesis-related genes, BR-related genes, reactive oxygen species pathway genes, and VLCFA synthesis genes. It was demonstrated that GhMYB30 may regulate fiber development through multiple pathways. Additionally, GhMYB46 was confirmed to be a target gene of GhMYB30 by EMSA, and GhMYB46 was significantly increased in GhMYB30-silenced lines, indicating that GhMYB30 inhibited GhMYB46 expression. Overall, these results revealed that GhMUR3 under the regulation of GhMYB30 and plays an essential role in cotton fiber elongation and secondary wall thickening. Additionally, GhMYB30 plays an important role in the regulation of fiber development and regulates fiber secondary wall synthesis by inhibiting the expression of GhMYB46.