Molecular traits of MAPK kinases and the regulatory mechanism of GhMAPKK5 alleviating drought/salt stress in cotton.

Mitogen-activated protein kinase kinases (MAPKKs) play a critical role in the mitogen-activated protein kinase (MAPK) signaling pathway, transducing external stimuli into intracellular responses and enabling plant adaptation to environmental challenges. Most research has focused on the model plant Arabidopsis (Arabidopsis thaliana). The systematic analysis and characterization of MAPKK genes across different plant species, particularly in cotton (Gossypium hirsutum), are somewhat limited. Here, we identified MAPKK family members from 66 different species, which clustered into 5 different sub-groups, and MAPKKs from four cotton species clustered together. Through further bioinformatic and expression analysis, GhMAPKK5 was identified as the most responsive MAPKK member to salt and drought stress among the 23 MAPKKs identified in Gossypium hirsutum. Silencing GhMAPKK5 in cotton through virus-induced gene silencing (VIGS) led to quicker wilting under salt and drought conditions, while overexpressing GhMAPKK5 in Arabidopsis enhanced root growth and seed germination under these stresses, demonstrating GhMAPKK5's positive role in stress tolerance. Transcriptomics and Yeast-Two-Hybrid assays revealed a MAPK cascade signal module comprising GhMEKK (Mitogen-activated protein kinase kinase kinases)3/8/31-GhMAPKK5-GhMAPK11/23. This signaling cascade may play a role in managing drought and salt stress by regulating transcription factor genes, such as WRKYs, which are involved in the biosynthesis and transport pathways of ABA, proline, and RALF. This study is highly important for further understanding the regulatory mechanism of MAPKK in cotton, contributing to its stress tolerance and offering potential in targets for genetic enhancement.

Functional characterization of NBS-LRR genes reveals an NBS-LRR gene that mediates resistance against Fusarium wilt.

BACKGROUND: Most disease resistance (R) genes in plants encode proteins that contain leucine-rich-repeat (LRR) and nucleotide-binding site (NBS) domains, which belong to the NBS-LRR family. The sequenced genomes of Fusarium wilt-susceptible Vernicia fordii and its resistant counterpart, Vernicia montana, offer significant resources for the functional characterization and discovery of novel NBS-LRR genes in tung tree. RESULTS: Here, we identified 239 NBS-LRR genes across two tung tree genomes: 90 in V. fordii and 149 in V. montana. Five VmNBS-LRR paralogous were predicted in V. montana, and 43 orthologous were detected between V. fordii and V. montana. The orthologous gene pair Vf11G0978-Vm019719 exhibited distinct expression patterns in V. fordii and V. montana: Vf11G0978 showed downregulated expression in V. fordii, while its orthologous gene Vm019719 demonstrated upregulated expression in V. montana, indicating that this pair may be responsible for the resistance to Fusarium wilt in V. montana. Vm019719 from V. montana, activated by VmWRKY64, was shown to confer resistance to Fusarium wilt in V. montana by a virus-induced gene silencing (VIGS) experiment. However, in the susceptible V. fordii, its allelic counterpart, Vf11G0978, exhibited an ineffective defense response, attributed to a deletion in the promoter's W-box element. CONCLUSIONS: This study provides the first systematic analysis of NBS-LRR genes in the tung tree and identifies a candidate gene that can be utilized for marker-assisted breeding to control Fusarium wilt in V. fordii.

Transcriptomics and virus-induced gene silencing identify defence-related genes during Ralstonia solanacearum infection in resistant and susceptible tobacco.

Bacterial wilt (BW) caused by Ralstonia solanacearum is a globally prevalent bacterial soil-borne disease. In this study, transcriptome sequencing were subjected to roots after infection with the R. solanacearum in the resistant and susceptible tobacco variety. DEGs that responded to R. solanacearum infection in both resistant and susceptible tobacco contributed to pectinase and peroxidase development and were enriched in plant hormone signal transduction, signal transduction and MAPK signalling pathway KEGG terms. Core DEGs in the resistant tobacco response to R. solanacearum infection were enriched in cell wall, membrane, abscisic acid and ethylene terms. qRT-PCR indicated that Nitab4.5_0004899g0110, Nitab4.5_0004234g0080 and Nitab4.5_0001439g0050 contributed to the response to R. solanacearum infection in different resistant and susceptible tobacco. Silencing the p450 gene Nitab4.5_0001439g0050 reduced tobacco resistance to bacterial wilt. These results improve our understanding of the molecular mechanism of BW resistance in tobacco and solanaceous plants.

Genome-wide identification of the TIFY gene family in tobacco and expression analysis in response to Ralstonia solanacearum infection.

The TIFY gene family plays an essential role in plant development and abiotic and biotic stress responses. In this study, genome-wide identification of TIFY members in tobacco and their expression pattern analysis in response to Ralstonia solanacearum infection were performed. A total of 33 TIFY genes were identified, including the TIFY, PPD, ZIM&ZML and JAZ subfamilies. Promoter analysis results indicated that a quantity of light-response, drought-response, SA-response and JA-response cis-elements exist in promoter regions. The TIFY gene family exhibited expansion and possessed gene redundancy resulting from tobacco ploidy change. In addition, most NtTIFYs equivalently expressed in roots, stems and leaves, while NtTIFY1, NtTIFY4, NtTIFY18 and NtTIFY30 preferentially expressed in roots. The JAZ III clade showed significant expression changes after inoculation with R. solanacearum, and the expression of NtTIFY7 in resistant varieties, compared with susceptible varieties, was more stably induced. Furthermore, NtTIFY7-silenced plants, compared with the control plants, were more susceptible to bacterial wilt. These results lay a foundation for exploring the evolutionary history of TIFY gene family and revealing gene function of NtTIFYs in tobacco bacterial wilt resistance.

Interaction of Whitefly Effector G4 with Tomato Proteins Impacts Whitefly Performance.

The phloem-feeding insect Bemisia tabaci is an important pest, responsible for the transmission of several crop-threatening virus species. While feeding, the insect secretes a cocktail of effectors to modulate plant defense responses. Here, we present a set of proteins identified in an artificial diet on which B. tabaci was salivating. We subsequently studied whether these candidate effectors can play a role in plant immune suppression. Effector G4 was the most robust suppressor of an induced- reactive oxygen species (ROS) response in Nicotiana benthamiana. In addition, G4 was able to suppress ROS production in Solanum lycopersicum (tomato) and Capsicum annuum (pepper). G4 localized predominantly in the endoplasmic reticulum in N. benthamiana leaves and colocalized with two identified target proteins in tomato: REF-like stress related protein 1 (RSP1) and meloidogyne-induced giant cell protein DB141 (MIPDB141). Silencing of MIPDB141 in tomato reduced whitefly fecundity up to 40%, demonstrating that the protein is involved in susceptibility to B. tabaci. Together, our data demonstrate that effector G4 impairs tomato immunity to whiteflies by interfering with ROS production and via an interaction with tomato susceptibility protein MIPDB141. [Formula: see text] Copyright © 2024 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Comprehensive analysis of pepper (Capsicum annuum) RAV genes family and functional identification of CaRAV1 under chilling stress.

BACKGROUND: Despite its known significance in plant abiotic stress responses, the role of the RAV gene family in the response of Capsicum annuum to chilling stress remains largely unexplored. RESULTS: In this study, we identified and characterized six members of the CaRAV gene subfamily in pepper plants through genome-wide analysis. Subsequently, the CaRAV subfamily was classified into four branches based on homology with Arabidopsis thaliana, each exhibiting relatively conserved domains within the branch. We discovered that light response elements accounted for the majority of CaRAVs, whereas low-temperature response elements were specific to the NGA gene subfamily. After pepper plants were subjected to chilling stress, qRT‒PCR analysis revealed that CaRAV1, CaRAV2 and CaNGA1 were significantly induced in response to chilling stress, indicating that CaRAVs play a role in the response to chilling stress. Using virus-induced gene silencing (VIGS) vectors, we targeted key members of the CaRAV gene family. Under normal growth conditions, the MDA content and SOD enzyme activity of the silenced plants were slightly greater than those of the control plants, and the REC activity was significantly greater than that of the control plants. The levels of MDA and electrolyte leakage were greater in the silenced plants after they were exposed to chilling stress, and the POD and CAT enzyme activities were significantly lower than those in the control, which was particularly evident under repeated chilling stress. In addition, the relative expression of CaPOD and CaCAT was greater in V2 plants upon repeated chilling stress, especially CaCAT was significantly greater in V2 plants than in the other two silenced plants, with 3.29 and 1.10 increases within 12 and 24 h. These findings suggest that CaRAV1 and CaNGA1 positively regulate the response to chilling stress. CONCLUSIONS: Silencing of key members of the CaRAV gene family results in increased susceptibility to chilling damage and reduced antioxidant enzyme activity in plants, particularly under repeated chilling stress. This study provides valuable information for understanding the classification and putative functions of RAV transcription factors in pepper plants.

The HD-ZIP II gene PaHAT14 increases cuticle deposition by down-regulating ERF gene PaERF105 in Phalaenopsis.

To analyze the gene involved in orchid floral development, a HD-Zip II gene PaHAT14, which specifically and highly expressed in perianth during early flower development was identified from Phalaenopsis. Transgenic Arabidopsis plants expressing 35S::PaHAT14 and 35S::PaHAT14+SRDX (fused with the repressor motif SRDX) exhibited similar altered phenotypes, including small leaves, early flowering, and bending petals with increased cuticle production. This suggests that PaHAT14 acts as a repressor. In contrast, transgenic Arabidopsis plants expressing 35S::PaHAT14+VP16 (fused with the activation domain VP16) exhibited curled leaves, late flowering, and folded petals with decreased cuticle production within hardly opened flowers. Additionally, the expression of the ERF gene DEWAX2, which negatively regulates cuticular wax biosynthesis, was down-regulated in 35S::PaHAT14 and 35S::PaHAT14+SRDX transgenic Arabidopsis, while it was up-regulated in 35S::PaHAT14+VP16 transgenic Arabidopsis. Furthermore, transient overexpression of PaHAT14 in Phalaenopsis petal/sepal increased cuticle deposition due to the down-regulation of PaERF105, a Phalaenopsis DEWAX2 orthologue. On the other hand, transient overexpression of PaERF105 decreased cuticle deposition, whereas cuticle deposition increased and the rate of epidermal water loss was reduced in PaERF105 VIGS Phalaenopsis flowers. Moreover, ectopic expression of PaERF105 not only produced phenotypes similar to those in 35S::PaHAT14+VP16 Arabidopsis but also compensated for the altered phenotypes observed in 35S::PaHAT14 and 35S::PaHAT14+SRDX Arabidopsis. These results suggest that PaHAT14 promotes cuticle deposition by negatively regulating downstream gene PaERF105 in orchid flowers.

PaWOX3 and PaWOX3B Regulate Flower Number and the Lip Symmetry of Phalaenopsis.

The standout characteristic of the orchid perianth is the transformation of the upper median petal into a distinctively formed lip, which gives orchid flowers their typically zygomorphic symmetry and makes them the most popular ornamental plants worldwide. To study orchid flower development, two WUSCHEL-related homeobox (WOX) genes, PaWOX3 and PaWOX3B, were identified in Phalaenopsis. PaWOX3 and PaWOX3B mRNAs accumulate abundantly during early reproductive development and perianths of young buds, significantly decreasing in mature flowers and absent in vegetative leaves and roots. PaWOX3 and PaWOX3B virus-induced gene silencing (VIGS) knockdown in Phalaenopsis significantly reduces floral bud numbers, suggesting that PaWOX3/PaWOX3B may be involved in flower initiation. Transgenic Arabidopsis ectopically expressing repressor forms of PaWOX3/PaWOX3B and their Oncidium ortholog, OnPRS, exhibit lateral organ development defects, implicating these genes likely have function in regulating growth and differentiation for lateral organs. Neither PaWOX3, PaWOX3B single nor PaWOX3/PaWOX3B double VIGS Phalaenopsis altered the flower morphology. Interestingly, double silencing of PaWOX3 or PaWOX3B with OAGL6-2, which controlled the identity/formation of lips, altered the symmetry of 'BigLip' produced in OAGL6-2 VIGS. This result indicated that the levels of PaWOX3/PaWOX3B are still sufficient to maintain the symmetry for the OAGL6-2 VIGS 'BigLip'. However, the symmetry of the OAGL6-2 VIGS 'BigLip' cannot be maintained once the expression of PaWOX3 or PaWOX3B is further reduced. Thus, in addition to controlling lip identity, this study further found that OAGL6-2 could cooperate with functionally redundant PaWOX3/PaWOX3B in maintaining the symmetric axis of lip.

Genome­wide analysis of cotton SCAMP genes and functional characterization of GhSCAMP2 and GhSCAMP4 in salt tolerance.

BACKGROUND: Secretory carrier membrane proteins (SCAMPs) form a family of integral membrane proteins and play a crucial role in mediating exocytosis in both animals and plants. While SCAMP genes have been studied in several plant species, their functions in cotton, particularly in response to abiotic stress, have not yet been reported. RESULTS: In this study, a total of 53 SCAMP genes were identified in G. arboreum, G. raimondii, G. hirsutum, and G. barbadense. These genes were classified into five groups based on a phylogenetic analysis with SCAMPs from Arabidopsis thaliana. The main factor driving the expansion of the SCAMP gene family in G. hirsutum is tandem and segmental duplication events. Using MEME, in addition to the conserved SCAMP domain, we identified 3-13 other domains in each GhSCAMP. The cis-element analysis suggested that GhSCAMPs were widely involved in cotton growth and development, and responses to abiotic stresses. RNA sequencing (RNA-Seq) and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) results showed that most GhSCAMPs were expressed highly in many tissues and had differential expression responses to drought, cold, and heat stresses. Knock-down of GhSCAMP2 and GhSCAMP4 by virus-induced gene silencing (VIGS) lead to a salt-sensitive phenotype and had a lower content of CAT, POD, and SOD. CONCLUSIONS: This study identified SCAMP genes in four cotton species, enhancing our understanding of the potential biological functions of SCAMPs. Additionally, we demonstrated that GhSCAMP2 and GhSCAMP4 positively regulate cotton tolerance to salt stress.

Comprehensive identification and systematical characterization of BRX gene family and the functional of GhBRXL5A in response to salt stress.

BACKGROUND: BRVIS RADIX (BRX) family is a small gene family with the highly conserved plant-specific BRX domains, which plays important roles in plant development and response to abiotic stress. Although BRX protein has been studied in other plants, the biological function of cotton BRX-like (BRXL) gene family is still elusive. RESULT: In this study, a total of 36 BRXL genes were identified in four cotton species. Whole genome or segmental duplications played the main role in the expansion of GhBRXL gene family during evolutionary process in cotton. These BRXL genes were clustered into 2 groups, α and ß, in which structural and functional conservation within same groups but divergence among different groups were found. Promoter analysis indicated that cis-elements were associated with the phytohormone regulatory networks and the response to abiotic stress. Transcriptomic analysis indicated that GhBRXL2A/2D and GhBRXL5A/5D were up/down-regulated in response to the different stress. Silencing of GhBRXL5A gene via virus-induced gene silencing (VIGS) improved salt tolerance in cotton plants. Furthermore, yeast two hybrid analysis suggested homotypic and heterotypic interactions between GhBRXL1A and GhBRXL5D. CONCLUSIONS: Overall, these results provide useful and valuable information for understanding the evolution of cotton GhBRXL genes and their functions in salt stress.

Genome-wide expression analysis of LACS gene family implies GhLACS25 functional responding to salt stress in cotton.

BACKGROUND: Long-chain acyl-coenzyme A synthetase (LACS) is a type of acylating enzyme with AMP-binding, playing an important role in the growth, development, and stress response processes of plants. RESULTS: The research team identified different numbers of LACS in four cotton species (Gossypium hirsutum, Gossypium barbadense, Gossypium raimondii, and Gossypium arboreum). By analyzing the structure and evolutionary characteristics of the LACS, the GhLACS were divided into six subgroups, and a chromosome distribution map of the family members was drawn, providing a basis for further research classification and positioning. Promoter cis-acting element analysis showed that most GhLACS contain plant hormones (GA, MeJA) or non-biological stress-related cis-elements. The expression patterns of GhLACS under salt stress treatment were analyzed, and the results showed that GhLACS may significantly participate in salt stress response through different mechanisms. The research team selected 12 GhLACSs responsive to salt stress for tissue expression analysis and found that these genes are expressed in different tissues. CONCLUSIONS: There is a certain diversity of LACS among different cotton species. Analysis of promoter cis-acting elements suggests that GhLACS may be involved in regulating plant growth, development and stress response processes. GhLACS25 was selected for in-depth study, which confirmed its significant role in salt stress response through virus-induced gene silencing (VIGS) and induced expression in yeast cells.

H3K36 methyltransferase GhKMT3;1a and GhKMT3;2a promote flowering in upland cotton.

BACKGROUND: The SET domain group (SDG) genes encode histone lysine methyltransferases, which regulate gene transcription by altering chromatin structure and play pivotal roles in plant flowering determination. However, few studies have investigated their role in the regulation of flowering in upland cotton. RESULTS: A total of 86 SDG genes were identified through genome-wide analysis in upland cotton (Gossypium hirsutum). These genes were unevenly distributed across 25 chromosomes. Cluster analysis revealed that the 86 GhSDGs were divided into seven main branches. RNA-seq data and qRT‒PCR analysis revealed that lysine methyltransferase 3 (KMT3) genes were expressed at high levels in stamens, pistils and other floral organs. Using virus-induced gene silencing (VIGS), functional characterization of GhKMT3;1a and GhKMT3;2a revealed that, compared with those of the controls, the GhKMT3;1a- and GhKMT3;2a-silenced plants exhibited later budding and flowering and lower plant heightwere shorter. In addition, the expression of flowering-related genes (GhAP1, GhSOC1 and GhFT) significantly decreased and the expression level of GhSVP significantly increased in the GhKMT3;1a- and GhKMT3;2a-silenced plants compared with the control plants. CONCLUSION: A total of 86 SDG genes were identified in upland cotton, among which GhKMT3;1a and GhKMT3;2a might regulate flowering by affecting the expression of GhAP1, GhSOC1, GhFT and GhSVP. These findings will provide genetic resources for advanced molecular breeding in the future.

Pan-genome analysis of GT64 gene family and expression response to Verticillium wilt in cotton.

BACKGROUND: The GT64 subfamily, belonging to the glycosyltransferase family, plays a critical function in plant adaptation to stress conditions and the modulation of plant growth, development, and organogenesis processes. However, a comprehensive identification and systematic analysis of GT64 in cotton are still lacking. RESULTS: This study used bioinformatics techniques to conduct a detailed investigation on the GT64 gene family members of eight cotton species for the first time. A total of 39 GT64 genes were detected, which could be classified into five subfamilies according to the phylogenetic tree. Among them, six genes were found in upland cotton. Furthermore, investigated the precise chromosomal positions of these genes and visually represented their gene structure details. Moreover, forecasted cis-regulatory elements in GhGT64s and ascertained the duplication type of the GT64 in the eight cotton species. Evaluation of the Ka/Ks ratio for similar gene pairs among the eight cotton species provided insights into the selective pressures acting on these homologous genes. Additionally, analyzed the expression profiles of the GT64 gene family. Overexpressing GhGT64_4 in tobacco improved its disease resistance. Subsequently, VIGS experiments conducted in cotton demonstrated reduced disease resistance upon silencing of the GhGT64_4, may indicate its involvement in affecting lignin and jasmonic acid biosynthesis pathways, thus impacting cotton resistance. Weighted Gene Co-expression Network Analysis (WGCNA) revealed an early immune response against Verticillium dahliae in G. barbadense compared to G. hirsutum. Quantitative Reverse Transcription Polymerase Chain Reaction (qRT-PCR) analysis indicated that some GT64 genes might play a role under various biotic and abiotic stress conditions. CONCLUSIONS: These discoveries enhance our knowledge of GT64 family members and lay the groundwork for future investigations into the disease resistance mechanisms of this gene in cotton.

Cy-1, a major QTL for tomato leaf curl New Delhi virus resistance, harbors a gene encoding a DFDGD-Class RNA-dependent RNA polymerase in cucumber (Cucumis sativus).

BACKGROUND: Tomato leaf curl New Delhi virus (ToLCNDV) (family Geminiviridae, genus Begomovirus) is a significant threat to cucumber (Cucumis sativus) production in many regions. Previous studies have reported the genetic mapping of loci related to ToLCNDV resistance, but no resistance genes have been identified. RESULTS: We conducted map-based cloning of the ToLCNDV resistance gene in cucumber accession No.44. Agroinfiltration and graft-inoculation analyses confirmed the resistance of No.44 to ToLCNDV isolates from the Mediterranean and Asian countries. Initial mapping involving two rounds of phenotyping with two independent F2 populations generated by crossing the begomovirus-susceptible cultivar SHF and No.44 consistently detected major quantitative trait loci (QTLs) on chromosomes 1 and 2 that confer resistance to ToLCNDV. Fine-mapping of Cy-1, the dominant QTL on chromosome 1, using F3 populations narrowed the candidate region to a 209-kb genomic segment harboring 24 predicted genes. Among these genes, DFDGD-class RNA-dependent RNA polymerase (CsRDR3), an ortholog of Ty-1/Ty-3 of tomato and Pepy-2 of capsicum, was found to be a strong candidate conferring ToLCNDV resistance. The CsRDR3 sequence of No.44 contained multiple amino acid substitutions; the promoter region of CsRDR3 in No.44 had a large deletion; and the CsRDR3 transcript levels were greater in No.44 than in SHF. Virus-induced gene silencing (VIGS) of CsRDR3 using two chromosome segment substitution lines harboring chromosome 1 segments derived from No.44 compromised resistance to ToLCNDV. CONCLUSIONS: Forward and reverse genetic approaches identified CsRDR3, which encodes a DFDGD-class RNA-dependent RNA polymerase, as the gene responsible for ToLCNDV resistance at the major QTL Cy-1 on chromosome 1 in cucumber. Marker-assisted breeding of ToLCNDV resistance in cucumber will be expedited by using No.44 and the DNA markers developed in this study.

Identification and virus-induced gene silencing (VIGS) analysis of methyltransferase affecting tomato (Solanum lycopersicum) fruit ripening.

MAIN CONCLUSION: Six methyltransferase genes affecting tomato fruit ripening were identified through genome-wide screening, VIGS assay, and expression pattern analysis. The data provide the basis for understanding new mechanisms of methyltransferases. Fruit ripening is a critical stage for the formation of edible quality and seed maturation, which is finely modulated by kinds of factors, including genetic regulators, hormones, external signals, etc. Methyltransferases (MTases), important genetic regulators, play vital roles in plant development through epigenetic regulation, post-translational modification, or other mechanisms. However, the regulatory functions of numerous MTases except DNA methylation in fruit ripening remain limited so far. Here, six MTases, which act on different types of substrates, were identified to affect tomato fruit ripening. First, 35 MTase genes with relatively high expression at breaker (Br) stage of tomato fruit were screened from the tomato MTase gene database encompassing 421 genes totally. Thereafter, six MTase genes were identified as potential regulators of fruit ripening via virus-induced gene silencing (VIGS), including four genes with a positive regulatory role and two genes with a negative regulatory role, respectively. The expression of these six MTase genes exhibited diverse patterns during the fruit ripening process, and responded to various external ripening-related factors, including ethylene, 1-methylcyclopropene (1-MCP), temperature, and light exposure. These results help to further elaborate the biological mechanisms of MTase genes in tomato fruit ripening and enrich the understanding of the regulatory mechanisms of fruit ripening involving MTases, despite of DNA MTases.

Indole-3 acetic acid negatively regulates rose black spot disease resistance through antagonizing the salicylic acid signaling pathway via jasmonic acid.

MAIN CONCLUSION: IAA cooperates with JA to inhibit SA and negatively regulates rose black spot disease resistance. Black spot disease caused by the fungus Marssonina rosae is the most prevalent and severe ailment in rose cultivation, leading to the appearance of black spots on leaves and eventual leaf fall, significantly impacting the utilization of roses in gardens. Salicylic acid (SA) and jasmonic acid (JA) are pivotal hormones that collaborate with indole-3 acetic acid (IAA) in regulating plant defense responses; however, the detailed mechanisms underlying the induction of black spot disease resistance by IAA, JA, and SA remain unclear. In this study, transcript analysis was conducted on resistant (R13-54) and susceptible (R12-26) lines following M. rosae infection. In addition, the impact of exogenous interference with IAA on SA- and JA-mediated disease resistance was examined. The continuous accumulation of JA, in synergy with IAA, inhibited activation of the SA signaling pathway in the early infection stage, thereby negatively regulating the induction of effective resistance to black spot disease. IAA administration alleviated the inhibition of SA on JA to negatively regulate the resistance of susceptible strains by further enhancing the synthesis and accumulation of JA. However, IAA did not contribute to the negative regulation of black spot resistance when high levels of JA were inhibited. Virus-induced gene silencing of RcTIFY10A, an inhibitor of the JA signaling pathway, further suggested that IAA upregulation led to a decrease in disease resistance, a phenomenon not observed when the JA signal was inhibited. Collectively, these findings indicate that the IAA-mediated negative regulation of black spot disease resistance relies on activation of the JA signaling pathway.

Co-localization and analysis of miR477b with fiber length quantitative trait loci in cotton.

Cotton is an important cash crop for the textile industry. However, the understanding of natural genetic variation of fiber elongation in relation to miRNA is lacking. A miRNA gene (miR477b) was found to co-localize with a previously mapped fiber length (FL) quantitative trait locus (QTL). The miR477b was differentially expressed during fiber elongation between two backcross inbred lines (BILs) differing in FL and its precursor sequences. Bioinformatics and qRT-PCR analysis were further used to analyse the miRNA genes, which could produce mature miR477b. Cotton plants with virus-induced gene silencing (VIGS) constructs to over-express the allele of miR477b from the BIL with longer fibers had significantly longer fibers as compared with negative control plants, while the VIGS plants with suppressed miRNA expression had significantly shorter fibers. The expression level of the target gene (DELLA) and related genes (RDL1 and EXPA1 for DELLA through HOX3 protein) in the two BILs and/or the VIGS plants were generally congruent, as expected. This report represents one of the first comprehensive studies to integrate QTL linkage mapping and physical mapping of small RNAs with both small and mRNA transcriptome analysis, followed by VIGS, to identify candidate small RNA genes affecting the natural variation of fiber elongation in cotton.

Gene identification, expression analysis, and molecular docking of SAT and OASTL in the metabolic pathway of selenium in Cardamine hupingshanensis.

KEY MESSAGE: Identification of selenium stress-responsive expression and molecular docking of serine acetyltransferase (SAT) and O-acetyl serine (thiol) lyase (OASTL) in Cardamine hupingshanensis. A complex coupled with serine acetyltransferase (SAT) and O-acetyl serine (thiol) lyase (OASTL) is the key enzyme that catalyzes selenocysteine (Sec) synthesis in plants. The functions of SAT and OASTL genes were identified in some plants, but it is still unclear whether SAT and OASTL are involved in the selenium metabolic pathway in Cardamine hupingshanensis. In this study, genome-wide identification and comparative analysis of ChSATs and ChOASTLs were performed. The eight ChSAT genes were divided into three branches, and the thirteen ChOASTL genes were divided into four branches by phylogenetic analysis and sequence alignment, indicating the evolutionary conservation of the gene structure and its association with other plant species. qRT-PCR analysis showed that the ChSAT and ChOASTL genes were differentially expressed in different tissues under various selenium levels, suggesting their important roles in Sec synthesis. The ChSAT1;2 and ChOASTLA1;2 were silenced by the VIGS system to investigate their involvement in selenium metabolites in C. hupingshanensis. The findings contribute to understanding the gene functions of ChSATs and ChOASTLs in the selenium stress and provide a reference for further exploration of the selenium metabolic pathway in plants.

GhiPLATZ17 and GhiPLATZ22, zinc-dependent DNA-binding transcription factors, promote salt tolerance in upland cotton.

KEY MESSAGE: The utilization of transcriptome analysis, functional validation, VIGS, and DAB techniques have provided evidence that GhiPLATZ17 and GhiPLATZ22 play a pivotal role in improving the salt tolerance of upland cotton. PLATZ (Plant AT-rich sequences and zinc-binding proteins) are known to be key regulators in plant growth, development, and response to salt stress. In this study, we comprehensively analyzed the PLATZ family in ten cotton species in response to salinity stress. Gossypium herbaceum boasts 25 distinct PLATZ genes, paralleled by 24 in G. raimondii, 25 in G. arboreum, 46 in G. hirsutum, 48 in G. barbadense, 43 in G. tomentosum, 67 in G. mustelinum, 60 in G. darwinii, 46 in G. ekmanianum, and a total of 53 PLATZ genes attributed to G. stephensii. The PLATZ gene family shed light on the hybridization and allopolyploidy events that occurred during the evolutionary history of allotetraploid cotton. Ka/Ks analysis suggested that the PLATZ gene family underwent intense purifying selection during cotton evolution. Analysis of synteny and gene collinearity revealed a complex pattern of segmental and dispersed duplication events to expand PLATZ genes in cotton. Cis-acting elements and gene expressions revealed that GhiPLATZ exhibited salt stress resistance. Transcriptome analysis, functional validation, virus-induced gene silencing (VIGS), and diaminobenzidine staining (DAB) demonstrated that GhiPLATZ17 and GhiPLATZ22 enhance salt tolerance in upland cotton. The study can potentially advance our understanding of identifying salt-resistant genes in cotton.

GhGASA14 regulates the flowering time of upland cotton in response to GA3.

KEY MESSAGE: The silencing of GhGASA14 and the identification of superior allelic variation in its coding region indicate that GhGASA14 may positively regulate flowering and the response to GA3. Gibberellic acid-stimulated Arabidopsis (GASA), a member of the gibberellin-regulated short amino acid family, has been extensively investigated in several plant species and found to be critical for plant growth and development. However, research on this topic in cotton has been limited. In this study, we identified 38 GhGASAs that were dispersed across 18 chromosomes in upland cotton, and all of these genes had a GASA core domain. Transcriptome expression patterns and qRT-PCR results revealed that GhGASA9 and GhGASA14 exhibited upregulated expression not only in the floral organs but also in the leaves of early-maturing cultivars. The two genes were functionally characterized by virus-induced gene silencing (VIGS), and the budding and flowering times after silencing the target genes were later than those of the control (TRV:00). Compared with that in the water-treated group (MOCK), the flowering period of the different fruiting branches in the GA3-treated group was more concentrated. Interestingly, allelic variation was detected in the coding sequence of GhGASA14 between early-maturing and late-maturing accessions, and the frequency of this favorable allele was greater in high-latitude cotton cultivars than in low-latitude ones. Additionally, a significant linear relationship was observed between the expression level of GhGASA14 and flowering time among the 12 upland cotton accessions. Taken together, these results indicated that GhGASA14 may positively regulate flowering time and respond to GA3. These findings could lead to the use of valuable genetic resources for breeding early-maturing cotton cultivars in the future.