The GhMYB36 transcription factor confers resistance to biotic and abiotic stress by enhancing PR1 gene expression in plants

The MYB transcription factor OsMYBxoc1 regulates resistance to Xoc by directly repressing transcription of the iron transport gene OsNRAMP5 in rice

Bacterial leaf streak caused by Xanthomonas oryzae pv. oryzicola (Xoc) is a continuous threat to rice cultivation, leading to substantial yield losses with socioeconomic implications. Iron ions are essential mineral nutrients for plant growth, but little information is available on how they influence mechanisms of rice immunity against Xoc. Here, we investigated the role of the myeloblastosis-related (MYB) transcriptional repressor OsMYBxoc1 in modulation of rice resistance through control of iron ion transport. Overexpression of OsMYBxoc1 significantly increased rice resistance, whereas OsMYBxoc1 RNA-interference lines and knockout mutants showed the opposite result. Suppression of OsMYBxoc1 expression dampened the immune response induced by pathogen-associated molecular patterns. We demonstrated that OsMYBxoc1 binds specifically to the OsNRAMP5 promoter and represses transcription of OsNRAMP5. OsNRAMP5, a negative regulator of rice resistance to bacterial leaf streak, possesses metal ion transport activity, and inhibition of OsMYBxoc1 expression increased the iron ion content in rice. Activity of the ion-dependent H2O2 scavenging enzyme catalase was increased in plants with suppressed expression of OsMYBxoc1 or overexpression of OsNRAMP5. We found that iron ions promoted Xoc infection and interfered with the production of reactive oxygen species induced by Xoc. The type III effector XopAK directly inhibited OsMYBxoc1 transcription, indicating that the pathogen may promote its own proliferation by relieving restriction of iron ion transport in plants. In addition, iron complemented the pathogenicity defects of the RS105_ΔXopAK mutant strain, further confirming that iron utilization by Xoc may be dependent upon XopAK. In conclusion, our study reveals a novel mechanism by which OsMYBxoc1 modulates rice resistance by regulating iron accumulation and demonstrates that Xoc can accumulate iron ions by secreting the effector XopAK to promote its own infection.

Pathogenesis related-1 proteins in plant defense: regulation and functional diversity

Climate change-related environmental stresses can negatively impact crop productivity and pose a threat to sustainable agriculture. Plants have a remarkable innate ability to detect a broad array of environmental cues, including stresses that trigger stress-induced regulatory networks and signaling pathways. Transcriptional activation of plant pathogenesis related-1 (PR-1) proteins was first identified as an integral component of systemic acquired resistance in response to stress. Consistent with their central role in immune defense, overexpression of PR-1s in diverse plant species is frequently used as a marker for salicylic acid (SA)-mediated defense responses. Recent advances demonstrated how virulence effectors, SA signaling cascades, and epigenetic modifications modulate PR-1 expression in response to environmental stresses. We and others showed that transcriptional regulatory networks involving PR-1s could be used to improve plant resilience to stress. Together, the results of these studies have re-energized the field and provided long-awaited insights into a possible function of PR-1s under extreme environmental stress.

The MYB Transcription Factor GmMYB78 Negatively Regulates Phytophthora sojae Resistance in Soybean

Phytophthora root rot is a devastating disease of soybean caused by Phytophthora sojae. However, the resistance mechanism is not yet clear. Our previous studies have shown that GmAP2 enhances sensitivity to P. sojae in soybean, and GmMYB78 is downregulated in the transcriptome analysis of GmAP2-overexpressing transgenic hairy roots. Here, GmMYB78 was significantly induced by P. sojae in susceptible soybean, and the overexpressing of GmMYB78 enhanced sensitivity to the pathogen, while silencing GmMYB78 enhances resistance to P. sojae, indicating that GmMYB78 is a negative regulator of P. sojae. Moreover, the jasmonic acid (JA) content and JA synthesis gene GmAOS1 was highly upregulated in GmMYB78-silencing roots and highly downregulated in overexpressing ones, suggesting that GmMYB78 could respond to P. sojae through the JA signaling pathway. Furthermore, the expression of several pathogenesis-related genes was significantly lower in GmMYB78-overexpressing roots and higher in GmMYB78-silencing ones. Additionally, we screened and identified the upstream regulator GmbHLH122 and downstream target gene GmbZIP25 of GmMYB78. GmbHLH122 was highly induced by P. sojae and could inhibit GmMYB78 expression in resistant soybean, and GmMYB78 was highly expressed to activate downstream target gene GmbZIP25 transcription in susceptible soybean. In conclusion, our data reveal that GmMYB78 triggers soybean sensitivity to P. sojae by inhibiting the JA signaling pathway and the expression of pathogenesis-related genes or through the effects of the GmbHLH122-GmMYB78-GmbZIP25 cascade pathway.

StoMYB41 positively regulates the Solanum torvum response to Verticillium dahliae in an ABA dependent manner

MYB transcription factor despite their solid involvement in growth are potent regulator of plant stress response. Herein, we identified a MYB gene named as StoMYB41 in a wild eggplant species Solanum torvum. The expression level of StoMYB41 was higher in root than the tissues including stem, leaf, and seed. It induced significantly by Verticillium dahliae inoculation. StoMYB41 was localized in the nucleus and exhibited transcriptional activation activity. Silencing of StoMYB41 enhanced susceptibility of Solanum torvum against Verticillium dahliae, accompanied by higher disease index. The significant down-regulation of resistance marker gene StoABR1 comparing to the control plants was recorded in the silenced plants. Moreover, transient expression of StoMYB41 could trigger intense hypersensitive reaction mimic cell death, darker DAB and trypan blue staining, higher ion leakage, and induced the expression levels of StoABR1 and NbDEF1 in the leaves of Solanum torvum and Nicotiana benthamiana. Taken together, our data indicate that StoMYB41 acts as a positive regulator in Solanum torvum against Verticillium wilt.

A systematic analysis of ARM genes revealed that GhARM144 regulates the resistance against Verticillium dahliae via interaction with GhOSM34

Proteins of the armadillo repeat gene family play important roles in plant pathogen response. Here, 169 armadillo (ARM) genes were identified in upland cotton (Gossypium hirsutum). Phylogenetic analysis grouped these into 11 subfamilies, with conserved protein structures within each subfamily. The results signify that the expansion of the gene family occurred via whole genome duplication and dispersed duplication. Expression profiling and network analysis suggest that GhARM144 may regulate cotton resistance to Verticillium dahliae. GhARM144 was upregulated in roots by V. dahliae infection or salicylic acid treatment. This upregulation indicates a negative regulatory role of GhARM144' in the cotton immune responses, potentially by manipulating salicylic acid biosynthesis. Protein interaction studies found that GhARM144 associates with an osmotin-like protein, GhOSM34, at the plasma membrane. Silencing GhOSM34 reduced the resistance to V. dahliae, suggesting it may play a positive regulatory role. The results demonstrate that GhARM144 modulates cotton immunity through interaction with GhOSM34 and salicylic acid signalling. Further study of these proteins may yield insights into disease resistance mechanisms in cotton and other plants.

Improvement of qualitative and quantitative traits in cotton under normal and stressed environments using genomics and biotechnological tools: A review

Due to the increasing demand for high-quality and high fiber-yielding cotton (Gossypium spp.), research into the development of stress-resilient cotton cultivars has acquired greater significance. Various biotic and abiotic stressors greatly affect cotton production and productivity, posing challenges to the future of the textile industry. Moreover, the content and quality of cottonseed oil can also potentially be influenced by future environmental conditions. Apart from conventional methods, genetic engineering has emerged as a potential tool to improve cotton fiber quality and productivity. Identification and modification of genome sequences and the expression levels of yield-related genes using genetic engineering approaches have enabled to increase both the quality and yields of cotton fiber and cottonseed oil. Herein, we evaluate the significance and molecular mechanisms associated with the regulation of cotton agronomic traits under both normal and stressful environmental conditions. In addition, the importance of gossypol, a toxic phenolic compound in cottonseed that can limit consumption by animals and humans, is reviewed and discussed.

Characterization and transformation of TtMYB1 transcription factor from Tritipyrum to improve salt tolerance in wheat

BACKGROUND

Common wheat (Triticum aestivum L.) is a worldwide cereal crop, which is an integral part of the diets of many countries. In addition, the MYB gene of wheat plays a role in the response to salt stress.

RESULTS

"Y1805" is a Tritipyrum variety that is relatively tolerant to salt. We used transcriptome analysis to show that the "Y1805" MYB gene was both highly expressed and sensitive to salt stress. Compared with control roots, the level of MYB expression during salt stress was higher, which rapidly decreased to control levels during the recovery process. MYB gene relative expression showed the highest levels in "Y1805" roots during salt stress, with the stems and then leaves being the next highest stressed tissues. The novel MYB gene (TtMYB1) was successfully cloned from "Y1805". It showed a coding sequence length of 783 bp with 95.79% homology with Tel2E01G633100 from Thinopyrum elongatum. TtMYB1 and MYB from Th. elongatum were clustered in the same branch using phylogenetic analysis, which indicated high similarities. The TtMYB1 gene is located in the nucleus. The coleoptile method was employed when a TtMYB1 overexpression vector was used during transformation into "1718" (common wheat). Under high salt stress, TtMYB1 leaves of overexpression lines had decreased wilting, when compared with wild-type (WT) plants. During normal conditions, salt stress, and recovery, the lengths of the roots and the heights of seedlings from the overexpression lines were found to be significantly greater than roots and seedlings of WT plants. In addition, during high salt stress, the overexpression lines showed that proline and soluble sugar levels were higher than that of WT plants, but with lower malondialdehyde levels. Forty-three proteins that interacted with TtMYB1 were identified using the yeast two-hybrid assay. Protein-protein interaction analyses indicated that most were SANT domain-containing and Wd repeat region domain-containing proteins. Among these proteins, ribosomal proteins were the main node. Abiotic stress-related terms (such as "carbonate dehydratase activity", "protein targeting peroxisomes", and "glutathione peroxidase activity") were enriched in GO analysis. In KEGG analysis, "carbohydrate metabolism", "environmental information processing", "genetic information processing", "signaling and cell precursors", and "energy metabolism" pathways were enriched.

CONCLUSION

The TtMYB1 gene might enhance salt tolerance by increasing proline and soluble sugar content and antioxidase activity in transgenic wheat. It therefore has the potential to enhance high salt tolerance in plants.

Cloning, Expression, and Functional Analysis of the MYB Transcription Factor SlMYB86-like in Tomato

MYB transcription factors (TFs) have been shown to play a key role in plant growth and development and are in response to various types of biotic and abiotic stress. Here, we clarified the structure, expression patterns, and function of a MYB TF, SlMYB86-like (Solyc06g071690) in tomato using an inbred tomato line exhibiting high resistance to bacterial wilt (Hm 2-2 (R)) and one susceptible line (BY 1-2 (S)). The full-length cDNA sequence of this gene was 1226 bp, and the open reading frame was 966 bp, which encoded 321 amino acids; its relative molecular weight was 37.05055 kDa; its theoretical isoelectric point was 7.22; it was a hydrophilic nonsecreted protein; and it had no transmembrane structures. The protein also contains a highly conserved MYB DNA-binding domain and was predicted to be localized to the nucleus. Phylogenetic analysis revealed that SlMYB86-like is closely related to SpMYB86-like in Solanum pennellii and clustered with other members of the family Solanaceae. Quantitative real-time PCR (qRT-PCR) analysis revealed that the expression of the SlMYB86-like gene was tissue specific and could be induced by Ralstonia solanacearum, salicylic acid, and jasmonic acid. The results of virus-induced gene silencing (VIGS) revealed that SlMYB86-like silencing decreased the resistance of tomato plants to bacterial wilt, suggesting that it positively regulates the resistance of tomatoes to bacterial wilt. Overall, these findings indicate that SlMYB86-like plays a key role in regulating the resistance of tomatoes to bacterial wilt.

RcMYB8 enhances salt and drought tolerance in rose (Rosa chinensis) by modulating RcPR5/1 and RcP5CS1

Plant Myeloblastosis (MYB) proteins function crucially roles upon variegated abiotic stresses. Nonetheless, their effects and mechanisms in rose (Rosa chinensis) are not fully clarified. In this study, we characterized the effects of rose RcMYB8 under salt and drought tolerances. For induction of the RcMYB8 expression, NaCl and drought stress treatment were adopted. Rose plants overexpressing RcMYB8 displayed enhanced tolerance to salinity and drought stress, while silencing RcMYB8 resulted in decreased tolerance, as evidenced by lowered intra-leaf electrolyte leakage and callose deposition, as well as photosynthetic sustainment under stressed conditions. Here, we further show that RcMYB8 binds similarly to the promoters of RcPR5/1 and RcP5C51 in vivo and in vitro. Inhibiting RcP5CS1 by virus-induced gene silencing led to decreased drought tolerance through the reactive oxygen species (ROS) homeostatic regulation. RcP5CS1-silenced plants showed an increase in ion leakage and reduce of proline content, together with the content of malondialdehyde (MDA) increased, lowered activities of Catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD). Our study highlights the transcriptional modulator role of RcMYB8 in drought and salinity tolerances, which bridges RcPR5/1 and RcP5CS1 by promoting ROS scavenging. Besides, it is probably applicable to the rose plant engineering for enhancing their abiotic stress tolerances.

GhTLP1, a thaumatin-like protein 1, improves Verticillium wilt resistance in cotton via JA, ABA and MAPK signaling pathway-plant pathways

Verticillium wilt of cotton is a very serious soil-borne disease and there is no effective control method. The mechanism of Gossypium hirsutum thaumatin-like protein 1(GhTLP1) in upland cotton regulating Verticillium wilt resistance has been an uncovered research approach. GhTLP1 is mainly localized in the cell wall. Overexpression of GhTLP1 significantly enhanced Arabidopsis plants resistance to Verticillium dahliae, while its homologous mutant tlp1 in Arabidopsis was more susceptible to the pathogen, and the heterologous complement line (EC) recovered resistance to V. dahliae. GhTLP1 responds to jasmonate acid (JA) and abscisic acid (ABA) hormones and regulates mitogen-activated protein kinase (MAPK) signaling pathway-plant pathway to enhance Arabidopsis plants resistance to V. dahliae. Silencing GhTLP1 resulted decrease in cotton plants resistance to V. dahliae. Moreover, the mutation of GhTLP1 at site Tyr97 and Tyr199 with the phosphorylation also decreased plant resistance to V. dahliae. Therefore, GhTLP1 phosphorylation was observed important in cotton plants against V. dahliae. Further analysis demonstrated that GhTLP1 interacted with gossypium hirsutum laccase 14 (GhLAC14) to enhance plants resistance to V. dahliae. Silencing GhLAC14 resulted decrease in cotton plants resistance to V. dahliae. Here, we propose that GhTLP1 is a potential molecular target for improving resistance to Verticillium wilt in cotton.

A module centered on the transcription factor Msn2 from arbuscular mycorrhizal fungus Rhizophagus irregularis regulates drought stress tolerance in the host plant

Arbuscular mycorrhizal (AM) fungi can form mutualistic endosymbiosis with > 70% of land plants for obtaining fatty acids and sugars, in return, AM fungi promote plant nutrients and water acquisition to enhance plant fitness. However, how AM fungi orchestrate its own signaling components in response to drought stress remains elusive. Here, we identify a transcription factor containing C2H2 zinc finger domains, RiMsn2 from Rhizophagus irregularis. To characterize the RiMsn2, we combined heterologous expression, subcellular localization in yeasts, and biochemical and molecular studies with reverse genetics approaches during the in planta phase. The results indicate that RiMsn2 is highly conserved across AM fungal species and induced during the early stages of symbiosis. It is significantly upregulated in mycorrhizal roots under severe drought conditions. The nucleus-localized RiMsn2 regulates osmotic homeostasis and trehalose contents of yeasts. Importantly, gene silencing analyses indicate that RiMsn2 is essential for arbuscule formation and enhances plant tolerance to drought stress. Results from yeasts and biochemical experiments suggest that the RiHog1-RiMsn2-STREs module controls the drought stress-responsive genes in AM fungal symbiont. In conclusion, our findings reveal that a module centered on the transcriptional activator RiMsn2 from AM fungus regulates drought stress tolerance in host plant.

A comprehensive overview of cotton genomics, biotechnology and molecular biological studies

Cotton is an irreplaceable economic crop currently domesticated in the human world for its extremely elongated fiber cells specialized in seed epidermis, which makes it of high research and application value. To date, numerous research on cotton has navigated various aspects, from multi-genome assembly, genome editing, mechanism of fiber development, metabolite biosynthesis, and analysis to genetic breeding. Genomic and 3D genomic studies reveal the origin of cotton species and the spatiotemporal asymmetric chromatin structure in fibers. Mature multiple genome editing systems, such as CRISPR/Cas9, Cas12 (Cpf1) and cytidine base editing (CBE), have been widely used in the study of candidate genes affecting fiber development. Based on this, the cotton fiber cell development network has been preliminarily drawn. Among them, the MYB-bHLH-WDR (MBW) transcription factor complex and IAA and BR signaling pathway regulate the initiation; various plant hormones, including ethylene, mediated regulatory network and membrane protein overlap fine-regulate elongation. Multistage transcription factors targeting CesA 4, 7, and 8 specifically dominate the whole process of secondary cell wall thickening. And fluorescently labeled cytoskeletal proteins can observe real-time dynamic changes in fiber development. Furthermore, research on the synthesis of cotton secondary metabolite gossypol, resistance to diseases and insect pests, plant architecture regulation, and seed oil utilization are all conducive to finding more high-quality breeding-related genes and subsequently facilitating the cultivation of better cotton varieties. This review summarizes the paramount research achievements in cotton molecular biology over the last few decades from the above aspects, thereby enabling us to conduct a status review on the current studies of cotton and provide strong theoretical support for the future direction.

Integrated transcriptomic and metabolomic analysis reveals the molecular basis of tissue-specific accumulation of bioactive steroidal alkaloids in Fritillaria unibracteata

Fritillaria unibracteata is an endangered medicinal plant whose bulb has been used as a Chinese herb to suppress cough, asthma and excessive phlegm for centuries. Steroidal alkaloids, which are synthesized via the steroid synthesis pathways, are their significant bioactive constituents. However, few studies on genes involved in steroidal alkaloid biosynthesis in F. unibracteata have been reported, mainly due to the lack of the F. unibracteata genome. In this paper, comparative transcriptomic and metabolomic analyses of four different tissues of F. unibracteata (leaves, flowers, stems, and bulbs) were performed. Imperialine, peiminine, and peimisine were among the significant bioactive compounds that were considerably abundant in bulb tissue, according to the metabolomic findings. Then, 83.60 Gb transcriptome sequencing of four different tissues was performed, of which one gene encoding phosphomevalonate kinase was directly functionally characterized to verify the accuracy of sequences obtained from the transcriptome. A total of 9217 differentially expressed unigenes (DEGs) were identified in four different tissues of F. unibracteata. GO and KEGG enrichments revealed that phenylpropanoid biosynthesis, MVA-mediated terpenoid backbone biosynthesis, and steroid biosynthesis were enriched in bulb tissue, whereas enrichment of MEP-mediated terpenoid backbone biosynthesis, photosynthesis, photosynthesis-antenna protein and carotenoid biosynthesis was observed in aerial tissues. Moreover, clustering analysis indicated that the downstream steroid biosynthesis pathway was more important in steroidal alkaloid biosynthesis compared to the upstream terpenoid backbone biosynthesis pathway. Hence, MVA-mediated biosynthesis of steroidal alkaloids was proposed, in which 15 bulb-clustered DEGs were positively correlated with a high accumulation of bioactive steroid alkaloids, further validating our proposal. In addition, 36 CYP450s showing a positive correlation with bioactive steroidal alkaloids provided candidate enzymes to catalyze the subsequent steps of steroidal alkaloid biosynthesis. In addition, the transcription factors and ABC transporters clustered in bulb tissue might be responsible for the regulation and transportation of steroidal alkaloid biosynthesis. Protein-protein interaction analysis implied a highly complex steroid alkaloid biosynthesis network in which delta (24)-sterol reductase might be one of the central catalysts. Based on the integrated transcriptome and metabolome, this current study is a first step in understanding the tissue-specific biosynthesis of steroidal alkaloids in F. unibracteata. Furthermore, key genes and regulators identified herein could facilitate metabolic engineering to improve steroidal alkaloids in F. unibracteata.

Functional study of BpCOI1 reveals its role in affecting disease resistance in birch

Plants interact with biotic and abiotic environments. Some of these interactions are detrimental including herbivory consumption and infections by microbial pathogens. The COI1 (coronatine insensitive 1) protein is the master controller of JA-regulated plant responses and plays a regulatory role in the plant defense response. However, there is little information on COI1 function in birch (Betula platyphylla × Betula pendula). Herein, we studied the F-box protein BpCOI1 which is located in the nucleus. To validate the function of this protein, we developed transgenic birch plants with overexpression or repression of BpCOI1 gene. Growth traits, such as tree height, ground diameter, number of lateral branches, did not change significantly among transgenic lines. Alternaria alternata treatment experiments indicated that low expression of BpCOI1 reduced disease resistance in birch. Furthermore, our results showed that low expression of BpCOI1 significantly reduced the sensitivity of plants to exogenous MeJA. Co-expression analysis showed gene expression patterns with similar characteristics. These genes may be closely related in function, or members involved in the same signaling pathway or physiological process with BpCOI 1. The results of transcriptome sequencing and co-expression analysis showed that BpCOI1 affects plant defense against Alternaria alternata by regulating jasmonates. This study reveals the role of BpCOI1 in disease resistance and proposes the possibility of controlling diseases through molecular breeding in birch.

The cotton miR171a-SCL6 module mediates plant resistance through regulating GhPR1 expression

Plants have developed intricate defense mechanisms in response to fluctuating environmental cues, including the use of microRNA (miRNA) as post-transcriptional regulators. However, the specific mechanisms through which miRNA contributes to disease resistance remain largely elusive. While the miR171-SCLs have been investigated in an eclectic array of plants, there has been a notable scarcity of research specifically focused on cotton (Gossypium hirsutum). In our previous miRNA-sequencing analysis, we found that ghr-miR171a displayed a differential response to infections by Verticillium dahliae. In this study, we further investigated the function of the miR171a-SCL6 module in cotton during V. dahliae infection. The ghr-miR171a was confirmed to direct the cleavage of GhSCL6 mRNA in the post-transcriptional process, as evidenced by 5' RLM-RACE, β-glucuronidase (GUS) histochemical staining and enzyme activity assay. Interestingly, we found that overexpressing ghr-miR171a reduced cotton plants' resistance to V. dahliae, while suppressing ghr-miR171a increased the plants' defense capacity. The GhSCL6 protein, when fused with green fluorescent protein (GFP), localizes in the cell nucleus, indicating its potential role in gene regulation. This was further corroborated by yeast two-hybrid assays, which verified GhSCL6's transcriptional activation ability. Through quantitative reverse transcriptase PCR (qRT-PCR), luciferase (LUC) fluorescence, and yeast one-hybrid assays, we found that GhSCL6 binds to the GT-box element of the GhPR1 promoter, activating its expression and thereby enhancing plant disease resistance. Taken together, our findings demonstrate that the cotton miR171a-SCL6 module regulates Verticillium wilt resistance in plants through the post-transcriptional process. This insight may offer new perspectives for disease resistance strategies in cotton.

BrMYB108 confers resistance to Verticillium wilt by activating ROS generation in Brassica rapa

Increasing plant resistance to Verticillium wilt (VW), which causes massive losses of Brassica rapa crops, is a challenge worldwide. However, few causal genes for VW resistance have been identified by forward genetic approaches, resulting in limited application in breeding. We combine a genome-wide association study in a natural population and quantitative trait locus mapping in an F2 population and identify that the MYB transcription factor BrMYB108 regulates plant resistance to VW. A 179 bp insertion in the BrMYB108 promoter alters its expression pattern during Verticillium longisporum (VL) infection. High BrMYB108 expression leads to high VL resistance, which is confirmed by disease resistance tests using BrMYB108 overexpression and loss-of-function mutants. Furthermore, we verify that BrMYB108 confers VL resistance by regulating reactive oxygen species (ROS) generation through binding to the promoters of respiratory burst oxidase genes (Rboh). A loss-of-function mutant of AtRbohF in Arabidopsis shows significant susceptibility to VL. Thus, BrMYB108 and its target ROS genes could be used as targets for genetic engineering for VL resistance of B. rapa.

The pivotal role of MYB transcription factors in plant disease resistance

MAIN CONCLUSION

MYB transcription factors are essential for diverse biology processes in plants. This review has focused on the potential molecular actions of MYB transcription factors in plant immunity. Plants possess a variety of molecules to defend against disease. Transcription factors (TFs) serve as gene connections in the regulatory networks controlling plant growth and defense against various stressors. As one of the largest TF families in plants, MYB TFs coordinate molecular players that modulate plant defense resistance. However, the molecular action of MYB TFs in plant disease resistance lacks a systematic analysis and summary. Here, we describe the structure and function of the MYB family in the plant immune response. Functional characterization revealed that MYB TFs often function either as positive or negative modulators towards different biotic stressors. Moreover, the MYB TF resistance mechanisms are diverse. The potential molecular actions of MYB TFs are being analyzed to uncover functions by controlling the expression of resistance genes, lignin/flavonoids/cuticular wax biosynthesis, polysaccharide signaling, hormone defense signaling, and the hypersensitivity response. MYB TFs have a variety of regulatory modes that fulfill pivotal roles in plant immunity. MYB TFs regulate the expression of multiple defense genes and are, therefore, important for increasing plant disease resistance and promoting agricultural production.

Acetylation of GhCaM7 enhances cotton resistance to Verticillium dahliae

Protein lysine acetylation is an important post-translational modification mechanism involved in cellular regulation in eukaryotes. Calmodulin (CaM) is a ubiquitous Ca²⁺ sensor in eukaryotes and is crucial for plant immunity, but it is so far unclear whether acetylation is involved in CaM-mediated plant immunity. Here, we found that GhCaM7 is acetylated upon Verticillium dahliae (V. dahliae) infection and a positive regulator of V. dahliae resistance. Overexpressing GhCaM7 in cotton and Arabidopsis enhances V. dahliae resistance and knocking-down GhCaM7 makes cotton more susceptible to V. dahliae. Transgenic Arabidopsis plants overexpressing GhCaM7 with mutation at the acetylation site are more susceptible to V. dahliae than transgenics overexpressing the wild-type GhCaM7, implying the importance of the acetylated GhCaM7 in response to V. dahliae infection. Yeast two-hybrid, bimolecular fluorescent complementation, luciferase complementation imaging, and coimmunoprecipitation assays demonstrated interaction between GhCaM7 and an osmotin protein GhOSM34 that was shown to have a positive role in V. dahliae resistance. GhCaM7 and GhOSM34 are co-localized in the cell membrane. Upon V. dahliae infection, the Ca²⁺ content reduces almost instantly in plants with downregulated GhCaM7 or GhOSM34. Down regulating GhOSM34 enhances accumulation of Na⁺ and increases cell osmotic pressure. Comparative transcriptomic analyses between cotton plants with an increased or reduced expression level of GhCaM7 and wild-type plants indicate the involvement of jasmonic acid signaling pathways and reactive oxygen species in GhCaM7-enabled disease resistance. Together, these results demonstrate the involvement of CaM protein in the interaction between cotton and V. dahliae, and more importantly, the involvement of the acetylated CaM in the interaction.

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.

GhMYB44 enhances stomatal closure to confer drought stress tolerance in cotton and Arabidopsis

MYB genes play crucial roles in plant response to abiotic stress. However, the function of MYB genes in cotton during abiotic stress is less well elucidated. Here, we found an R2R3-type MYB gene, GhMYB44, was induced by simulated drought (PEG6000) and ABA in three cotton varieties. After drought stress, the GhMYB44-silenced plants showed substantial changes at the physiological level, including significantly increased malondialdehyde content and decreased SOD activity. Silencing the GhMYB44 gene increased stomatal aperture and water loss rate, reduced plant drought tolerance. Transgenic Arabidopsis thaliana over-expressed GhMYB44 (GhMYB44-OE) enhanced resistance to mannitol-simulated osmotic stress. The stomatal aperture of the GhMYB44-OE Arabidopsis was significantly smaller than those of the wild type (WT), and the GhMYB44-OE Arabidopsis increased tolerance to drought stress. Transgenic Arabidopsis had higher germination rate under ABA treatment compared to WT, and the transcript levels of AtABI1, AtPP2CA and AtHAB1 were suppressed in GhMYB44-OE plants, indicating a potential role of GhMYB44 in the ABA signal pathway. These results showed that GhMYB44 acts as a positive regulator in plant response to drought stress, potentially useful for engineering drought-tolerant cotton.

Identification of the Function of the Pathogenesis-Related Protein GmPR1L in the Resistance of Soybean to Cercospora sojina Hara

Pathogenesis-related proteins, often used as molecular markers of disease resistance in plants, can enable plants to obtain systemic resistance. In this study, a gene encoding a pathogenesis-related protein was identified via RNA-seq sequencing analysis performed at different stages of soybean seedling development. Because the gene sequence showed the highest similarity with PR1L sequence in soybean, the gene was named GmPR1-9-like (GmPR1L). GmPR1L was either overexpressed or silenced in soybean seedlings through Agrobacterium-mediated transformation to examine the resistance of soybean to infection caused by Cercospora sojina Hara. The results revealed that GmPR1L-overexpressing soybean plants had a smaller lesion area and improved resistance to C. sojina infection, whereas GmPR1L-silenced plants had low resistance to C. sojina infection. Fluorescent real-time PCR indicated that overexpression of GmPR1L induced the expression of genes such as WRKY, PR9, and PR14, which are more likely to be co-expressed during C. sojina infection. Furthermore, the activities of SOD, POD, CAT, and PAL were significantly increased in GmPR1L-overexpressing soybean plants after seven days of infection. The resistance of the GmPR1L-overexpressing lines OEA1 and OEA2 to C. sojina infection was significantly increased from a neutral level in wild-type plants to a moderate level. These findings predominantly reveal the positive role of GmPR1L in inducing resistance to C. sojina infection in soybean, which may facilitate the production of improved disease-resistant soybean cultivars in the future.

GhMYB102 promotes drought resistance by regulating drought-responsive genes and ABA biosynthesis in cotton (Gossypium hirsutum L.)

The MYB transcription factor (TF) family is among the largest TF families and plays an important role in plant growth and stress response. However, few studies have investigated the role of the MYB gene in drought resistance in cotton. In this study, we analysed the drought transcriptomic data of cotton and identified that the GhMYB102 gene was significantly upregulated in upland cotton during the early stages of drought stress. Bioinformatics analysis showed that the amino acid sequence encoded by GhMYB102 contained two highly conserved MYB binding domains belonging to R2R3-MYB TFs. GhMYB102 was most closely related to AtMYB102. GhMYB102 is mainly expressed in roots and is induced by abiotic stresses and abscisic acid (ABA); it is localised in the nucleus and has transcriptional activation activity. Silencing of GhMYB102 decreased plant drought resistance. In addition, dual-luciferase assays and yeast single hybridisation analysis showed that GhMYB102 could directly bind the MYB motif elements in the promoter regions of GhNCED1 and GhZAT10. These results indicate that GhMYB102 plays a positive role in drought tolerance by regulating the expression of GhNCED1 and GhZAT10. Thus, GhMYB102 enhances drought resistance by participating in ABA biosynthesis or regulating the expression of drought-responsive genes.

Comprehensive Analysis of the INDETERMINATE DOMAIN (IDD) Gene Family and Their Response to Abiotic Stress in Zea mays

Transcription factors (TFs) are important regulators of numerous gene expressions due to their ability to recognize and combine cis-elements in the promoters of target genes. The INDETERMINATE DOMAIN (IDD) gene family belongs to a subfamily of C2H2 zinc finger proteins and has been identified only in terrestrial plants. Nevertheless, little study has been reported concerning the genome-wide analysis of the IDD gene family in maize. In total, 22 ZmIDD genes were identified, which can be distributed on 8 chromosomes in maize. On the basis of evolutionary relationships and conserved motif analysis, ZmIDDs were categorized into three clades (1, 2, and 3), each owning 4, 6, and 12 genes, respectively. We analyzed the characteristics of gene structure and found that 3 of the 22 ZmIDD genes do not contain an intron. Cis-element analysis of the ZmIDD promoter showed that most ZmIDD genes possessed at least one ABRE or MBS cis-element, and some ZmIDD genes owned the AuxRR-core, TCA-element, TC-rich repeats, and LTR cis-element. The Ka:Ks ratio of eight segmentally duplicated gene pairs demonstrated that the ZmIDD gene families had undergone a purifying selection. Then, the transcription levels of ZmIDDs were analyzed, and they showed great differences in diverse tissues as well as abiotic stresses. Furthermore, regulatory networks were constructed through the prediction of ZmIDD-targeted genes and miRNAs, which can inhibit the transcription of ZmIDDs. In total, 6 ZmIDDs and 22 miRNAs were discovered, which can target 180 genes and depress the expression of 9 ZmIDDs, respectively. Taken together, the results give us valuable information for studying the function of ZmIDDs involved in plant development and climate resilience in maize.

Genome-wide identification of the TIFY family reveals JAZ subfamily function in response to hormone treatment in Betula platyphylla

BACKGROUND

The TIFY family is a plant-specific gene family and plays an important role in plant growth and development. But few reports have been reported on the phylogenetic analysis and gene expression profiling of TIFY family genes in birch (Betula platyphylla).

RESULTS

In this study, we characterized TIFY family and identified 12 TIFY genes and using phylogeny and chromosome mapping analysis in birch. TIFY family members were divided into JAZ, ZML, PPD and TIFY subfamilies. Phylogenetic analysis revealed that 12 TIFY genes were clustered into six evolutionary branches. The chromosome distribution showed that 12 TIFY genes were unevenly distributed on 5 chromosomes. Some TIFY family members were derived from gene duplication in birch. We found that six JAZ genes from JAZ subfamily played essential roles in response to Methyl jasmonate (MeJA), the JAZ genes were correlated with COI1 under MeJA. Co-expression and GO enrichment analysis further revealed that JAZ genes were related to hormone. JAZ proteins involved in the ABA and SA pathways. Subcellular localization experiments confirmed that the JAZ proteins were localized in the nucleus. Yeast two-hybrid assay showed that the JAZ proteins may form homologous or heterodimers to regulate hormones.

CONCLUSION

Our results provided novel insights into biological function of TIFY family and JAZ subfamily in birch. It provides the theoretical reference for in-depth analysis of plant hormone and molecular breeding design for resistance.

SiMYBS3, Encoding a Setaria italica Heterosis-Related MYB Transcription Factor, Confers Drought Tolerance in Arabidopsis

Drought is a major limiting factor affecting grain production. Drought-tolerant crop varieties are required to ensure future grain production. Here, 5597 DEGs were identified using transcriptome data before and after drought stress in foxtail millet (Setaria italica) hybrid Zhangza 19 and its parents. A total of 607 drought-tolerant genes were screened through WGCNA, and 286 heterotic genes were screened according to the expression level. Among them, 18 genes overlapped. One gene, Seita.9G321800, encoded MYBS3 transcription factor and showed upregulated expression after drought stress. It is highly homologous with MYBS3 in maize, rice, and sorghum and was named SiMYBS3. Subcellular localization analysis showed that the SiMYBS3 protein was located in the nucleus and cytoplasm, and transactivation assay showed SiMYBS3 had transcriptional activation activity in yeast cells. Overexpression of SiMYBS3 in Arabidopsis thaliana conferred drought tolerance, insensitivity to ABA, and earlier flowering. Our results demonstrate that SiMYBS3 is a drought-related heterotic gene and it can be used for enhancing drought resistance in agricultural crop breeding.

Overexpression of the cotton trihelix transcription factor GhGT23 in Arabidopsis mediates salt and drought stress tolerance by binding to GT and MYB promoter elements in stress-related genes

Cotton (Gossypium hirsutum L.) is the world's most economically valuable textile crop. However, cotton plants are often subjected to numerous abiotic stresses that can dramatically limit yield. Trihelix transcription factors (TTFs) play important roles in abiotic stress responses in many plant species, and efforts to better understand their roles in cotton abiotic stress responses are ongoing. In this study, a member of the cotton TTF family (GhGT23) was functionally characterized. This protein contains a SANT domain and is a member of the SIP subfamily of TTF proteins. GhGT23 was significantly (p < 0.05) and highly expressed in cotton fiber compared to relatively low expression in other tissues. A significant (p < 0.05) increase in GhGT23 expression occurred in cotton seedlings within 12 hours of drought, salt, and ABA exposure. The GhGT23 protein localized in the nucleus but exhibited no signs of transactivation activity. GhGT23 overexpression in Arabidopsis conferred enhanced drought and salt stress tolerance. The expression of stress-related genes was higher in transgenic Arabidopsis expressing GhGT23 than in wild-type plants subjected to salt stress. The results of electrophoretic mobility shift assay revealed that GhGT23 could bind to the GT cis-elements GT-1Box (Box II), GT2-Box, GT3-Box, GT-3a (Site1-type), GT-3b, and Box as well as the MYB cis-elements MBS1 and MRE4. Our results demonstrate that GhGT23 positively regulates salt and drought stress responses, possibly by enhancing the expression of stress-related genes.

Overexpression of CaMYB78 transcription factor enhances resistance response in chickpea against Fusarium oxysporum and negatively regulates anthocyanin biosynthetic pathway

Chickpea, an important grain legume, suffers from considerable loss of yield due to Fusarium wilt disease. Inaccessibility of resistant gene pool among cultivars and lack of report of resistance, genes from alien sources have been the major constraints for resistance development in this valuable crop. However, along with some other transcription factors, MYB78 was significantly upregulated during chickpea-Fusarium interplay in resistant chickpea genotype. Being a highly recalcitrant species, the transformation of this important crop remained non-reproducible until recently. Following a tissue culture independent plumular meristem transformation protocol, introgression of CaMYB78 TF finally became feasible in chickpea. The overexpressed plants developed resistance against the pathogen but the anthocyanin production in transformed flowers was perturbed. In silico analyses of the anthocyanin biosynthetic key gene promoters reported the occurrence of multiple MYB-binding cis elements. Detailed molecular analyses establish the differential regulatory roles of CaMYB78, resistance response against Foc1 on one hand and suppression of pigmentation during flower development on the other, which is an innovative finding of its kind.

RcbHLH59-RcPRs module enhances salinity stress tolerance by balancing Na+/K+ through callose deposition in rose (Rosa chinensis)

Basic helix-loop-helix (bHLH) proteins play pivotal roles in plant growth, development, and stress responses. However, the molecular and functional properties of bHLHs have not been fully characterized. In this study, a novel XI subgroup of the bHLH protein gene RcbHLH59 was isolated and identified in rose (Rosa sp.). This gene was induced by salinity stress in both rose leaves and roots, and functioned as a transactivator. Accordingly, silencing RcbHLH59 affected the antioxidant system, Na ⁺/K ⁺ balance, and photosynthetic system, thereby reducing salt tolerance, while the transient overexpression of RcbHLH59 improved salinity stress tolerance. Additionally, RcbLHLH59 was found to regulate the expression of sets of pathogenesis-related (PR) genes in RcbHLH59-silenced (TRV-RcbHLH59) and RcbHLH59-overexpressing (RcbHLH59-OE) rose plants. The RcPR4/1 and RcPR5/1 transcript levels showed opposite changes in the TRV-RcbHLH59 and RcbHLH59-OE lines, suggesting that these two genes are regulated by RcbHLH59. Further analysis revealed that RcbHLH59 binds to the promoters of RcPR4/1 and RcPR5/1, and that the silencing of RcPR4/1 or RcPR5/1 led to decreased tolerance to salinity stress. Moreover, callose degradation- and deposition-related genes were impaired in RcPR4/1- or RcPR5/1-silenced plants, which displayed a salt tolerance phenotype by balancing the Na⁺/K⁺ ratio through callose deposition. Collectively, our data highlight a new RcbLHLH59-RcPRs module that positively regulates salinity stress tolerance by balancing Na⁺/K⁺ and through callose deposition in rose plants.

Recent progression and future perspectives in cotton genomic breeding

Upland cotton is an important global cash crop for its long seed fibers and high edible oil and protein content. Progress in cotton genomics promotes the advancement of cotton genetics, evolutionary studies, functional genetics, and breeding, and has ushered cotton research and breeding into a new era. Here, we summarize high-impact genomics studies for cotton from the last 10 years. The diploid Gossypium arboreum and allotetraploid Gossypium hirsutum are the main focus of most genetic and genomic studies. We next review recent progress in cotton molecular biology and genetics, which builds on cotton genome sequencing efforts, population studies, and functional genomics, to provide insights into the mechanisms shaping abiotic and biotic stress tolerance, plant architecture, seed oil content, and fiber development. We also suggest the application of novel technologies and strategies to facilitate genome-based crop breeding. Explosive growth in the amount of novel genomic data, identified genes, gene modules, and pathways is now enabling researchers to utilize multidisciplinary genomics-enabled breeding strategies to cultivate "super cotton", synergistically improving multiple traits. These strategies must rise to meet urgent demands for a sustainable cotton industry.

Transgenic Improvement for Biotic Resistance of Crops

Biotic constraints, including pathogenic fungi, viruses and bacteria, herbivory insects, as well as parasitic nematodes, cause significant yield loss and quality deterioration of crops. The effect of conventional management of these biotic constraints is limited. The advances in transgenic technologies provide a direct and directional approach to improve crops for biotic resistance. More than a hundred transgenic events and hundreds of cultivars resistant to herbivory insects, pathogenic viruses, and fungi have been developed by the heterologous expression of exogenous genes and RNAi, authorized for cultivation and market, and resulted in a significant reduction in yield loss and quality deterioration. However, the exploration of transgenic improvement for resistance to bacteria and nematodes by overexpression of endogenous genes and RNAi remains at the testing stage. Recent advances in RNAi and CRISPR/Cas technologies open up possibilities to improve the resistance of crops to pathogenic bacteria and plant parasitic nematodes, as well as other biotic constraints.

Advanced genes expression pattern greatly contributes to divergence in Verticillium wilt resistance between Gossypium barbadense and Gossupium hirsutum

Verticillium, representing one of the world's major pathogens, causes Verticillium wilt in important woody species, ornamentals, agricultural, etc., consequently resulting in a serious decline in production and quality, especially in cotton. Gossupium hirutum and Gossypium barbadense are two kinds of widely cultivated cotton species that suffer from Verticillium wilt, while G. barbadense has much higher resistance toward it than G. hirsutum. However, the molecular mechanism regarding their divergence in Verticillium wilt resistance remains largely unknown. In the current study, G. barbadense cv. Hai7124 and G. hirsutum acc. TM-1 were compared at 0, 12, 24, 48, 72, 96, 120, and 144 h post-inoculation (hpi) utilizing high throughput RNA-Sequencing. As a result, a total of 3,549 and 4,725 differentially expressed genes (DEGs) were identified, respectively. In particular, the resistant type Hai7124 displayed an earlier and faster detection and signaling response to the Verticillium dahliae infection and demonstrated higher expression levels of defense-related genes over TM-1 with respect to transcription factors, plant hormone signal transduction, plant-pathogen interaction, and nucleotide-binding leucine-rich repeat (NLR) genes. This study provides new insights into the molecular mechanisms of divergence in Verticillium wilt resistance between G. barbadense and G. hirsutum and important candidate genes for breeding V. dahliae resistant cotton cultivars.

Comparative transcriptome analysis unveiling reactive oxygen species scavenging system of Sonneratia caseolaris under salinity stress

Many mangrove forests have undergone major changes as a result of human activity and global climate change. Sonneratia caseolaris is a common tree located in inner mangroves, and its range extends inland along tidal creeks, as far as the influence of salinity extends. This study investigated the physiological and molecular response mechanisms of S. caseolaris by analyzing its antioxidant defense capacity, including its differentially expressed genes (DEGs) under similar salt stress conditions. Salt treatment significantly affected the osmoprotectants and lipid peroxidation in S. caseolaris seedlings, which increased proline (Pro) content by 31.01-54.90% during all sample periods and decreased malonaldehyde (MDA) content by 12.81 and 18.17% at 25 and 40 days under 3.0% NaCl treatment. Antioxidant enzyme activities increased significantly following 3.0% NaCl treatment. Transcriptome analysis following De novo assembly showed 26,498 matched unigenes. The results showed that 1,263 DEGs responded to transcription factors (TFs) and plant phytohormones and mediated oxidoreductase activity to scavenge reactive oxygen species (ROS) in the control vs. 3.0% NaCl comparison. In addition, the transcription levels of genes associated with auxin and ethylene signal transduction also changed. Under salt stress, ROS scavenging genes (POD, CAT, and APX) and part of AP2, MYB, NAC, C2C2, bHLH, and WRKY TFs were upregulated. This study identified important pathways and candidate genes involved in S. caseolaris salinity tolerance and provided suggestions for further research into the mechanisms of salt tolerance in S. caseolaris.

The heat shock factor GhHSFA4a positively regulates cotton resistance to Verticillium dahliae

Heat shock factors (HSFs) play a crucial role in the environmental stress responses of numerous plant species, including defense responses to pathogens; however, their role in cotton resistance to Verticillium dahliae remains unclear. We have previously identified several differentially expressed genes (DEGs) in Arabidopsis thaliana after inoculation with V. dahliae. Here, we discovered that GhHSFA4a in Gossypium hirsutum (cotton) after inoculation with V. dahliae shares a high identity with a DEG in A. thaliana in response to V. dahliae infection. Quantitative real-time PCR (qRT-PCR) analysis indicated that GhHSFA4a expression was rapidly induced by V. dahliae and ubiquitous in cotton roots, stems, and leaves. In a localization analysis using transient expression, GhHSFA4a was shown to be localized to the nucleus. Virus-induced gene silencing (VIGS) revealed that downregulation of GhHSFA4a significantly increased cotton susceptibility to V. dahliae. To investigate GhHSFA4a-mediated defense, 814 DEGs were identified between GhHSFA4a-silenced plants and controls using comparative RNA-seq analysis. The Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that DEGs were enriched in "flavonoid biosynthesis", "sesquiterpenoid and triterpenoid biosynthesis", "linoleic acid metabolism" and "alpha-linolenic acid metabolism". The expression levels of marker genes for these four pathways were triggered after inoculation with V. dahliae. Moreover, GhHSFA4a-overexpressing lines of A. thaliana displayed enhanced resistance against V. dahliae compared to that of the wild type. These results indicate that GhHSFA4a is involved in the synthesis of secondary metabolites and signal transduction, which are indispensable for innate immunity against V. dahliae in cotton.