CottonFGD: an integrated functional genomics database for cotton

Genome-wide identification unravels the role of the arabinogalactan peptide (AGP) gene family in cotton plant architecture

KEY MESSAGE

In our study, we identified the gene Gohir.A08G240900 as a potential target for regulating cotton plant height, providing a genetic basis for enhancing cotton morphology. Arabinogalactan peptides are a class of hydroxyproline-rich proteins widely distributed in plants that participate in many life processes, including growth and development, cell division and even plant reproductive development. In this study, we identified 122 members of the AGP gene family via genome-wide identification in six cotton species. Through phylogenetic tree analysis, the AGP family was divided into six different subgroups. A core yet variable region composed of proline, hydroxyproline, serine, threonine, and alanine (PAST) was identified among these members. Furthermore, Ka/Ks analysis revealed that the AGP gene family underwent multiple fragment duplication events. Additionally, we analyzed the 1.5 kb upstream cis-acting elements of all upland cotton family members and identified numerous functional elements associated with growth and development, suggesting a close relationship among the family members. The results of RT‒qPCR analysis revealed that the expression level of Gohir.A08G240900 was significantly different among the four upland cotton varieties, with significant differences in plant height. Virus-induced gene silencing (VIGS) experiments revealed that the height of Gohir.A08G240900 gene-silenced plants significantly decreased. The results revealed that Gohir.A08G240900 may affect plant growth and development and may be a potential functional gene regulating cotton plant height.

CRISPR/Cas9-mediated knockout of GhAMS11 and GhMS188 reveals key roles in tapetal development and pollen exine formation in upland cotton

The ABORTED MICROSPORES (AMS) gene is crucial for tapetal cell development and pollen formation, but its role in Upland cotton (Gossypium hirsutum) has not been previously documented. This study identified GhAMS11 as a key transcription factor, with its high expression specifically observed during the S4-S6 stages of anther development, a critical period for tapetal activity and pollen formation. Subcellular localization confirmed that GhAMS11 was located in the nucleus. CRISPR/Cas9 knockout of GhAMS11 resulted in pollen inviability, with mutants displaying abnormal tapetal development and defective pollen exine formation. TUNEL assays highlighted GhAMS11's involvement in proper tapetal programmed cell death (PCD). Additionally, GhAMS11 was found to activate GhMS188 expression, as demonstrated by dual-luciferase assays and EMSA assays, with their interaction confirmed through LCI assays, yeast two-hybrid assays and GST pull down assays. Deletion of GhMS188 led to pollen sterility, grain collapse, and impaired pollen exine formation. Thus, this research identified the bHLH transcription factor GhAMS11, addressing a gap in AMS gene research in Upland cotton, and elucidated its key regulatory role in pollen development in cooperation with GhMS188.

Identification of the cysteine-rich transmembrane module CYSTM family in upland cotton and functional analysis of GhCYSTM5_A in cold and drought stresses

Abiotic stress poses adverse impacts on cotton production, raising demands for a better understanding of stress-response mechanisms and developing strategies to improve plant performance to cope with stress. CYSTM (Cysteine-rich transmembrane module) is a widely distributed and conserved family in eukaryotes that performs potential functions in stress tolerance. However, CYSTM genes and their role in stress response is uncharacterized in cotton. Herein, we identified a total of 23 CYSTM genes from upland cotton. They underwent mainly segmental duplications and experienced purifying selection during evolution. Expression profiles revealed GhCYSTMs were closely related to abiotic stress response. Furthermore, GhCYSTM5_A overexpression enhanced the cold and drought tolerance of cotton, while RNAi-mediated knockdown of GhCYSTM5_A decreased stress tolerance. Transcriptome analysis revealed GhCYSTM5_A may contribute to cold and drought tolerance by regulating the expression of oxidative stress-related genes through MAPK signaling. GhCYSTM5_A, localized in the nucleus and cytoplasm interacted with a secreted cysteine-rich peptide GhGASA14. Moreover, GhGASA14 silencing rendered cotton plants vulnerable to cold and drought. These results suggested the potential functions of GhCYSTM genes in abiotic stress and a positive role of GhCYSTM5_A in cold and drought tolerance. This study sheds light on comprehensive characteristics of GhCYSTM, and provides candidate genes for genetic breeding.

Time-course RNA-seq analysis of upland cotton (Gossypium hirsutum L.) responses to Southern root-knot nematode (Meloidogyne incognita) during compatible and incompatible interactions

BACKGROUND

The Southern root-knot nematode (Meloidogyne incognita) poses a substantial threat to cotton (Gossypium hirsutum L.) by causing significant agricultural losses. Host plant resistance is the most plausible approach for minimizing these losses. QTL mapping and early transcriptomic studies have identified candidate genes within the QTL regions on chromosome 11 (qMi-C11) and chromosome 14 (qMi-C14). Although these QTL regions have been fine-mapped and candidate genes identified, expression profiling of Meloidogyne-Gossypium interactions across different stages of infection could further refine the list of candidate genes. This study advances our understanding of the molecular mechanisms underlying the resistance conferred by qMi-C11 and qMi-C14 against Southern root-knot nematode.

RESULTS

Using time-course RNA-seq analyses across nematode developmental phases, we uncovered transcriptomic events-both genome-wide and within QTL intervals-underlying defense responses during compatible interactions (with Cocker 201, a susceptible line) and incompatible interactions (with M-120 RNR, a resistant line). Basal defense responses were observed in both compatible and incompatible interactions, with stronger expression in the incompatible interaction. Nematode-responsive genes associated with defense pathways showed distinct dynamics, characterized by repression during compatible interactions and early induction, greater diversity, and heightened upregulation during incompatible interactions. This study uncovers a broad repertoire of disease resistance and putative resistance genes, as well as pathogenesis-related genes, ligands, and receptors, that are differentially expressed in response to nematode parasitism. Mapping of these genes across the cotton genome identified promising candidates, including Gh_A11G3090 (PUB21) and Gh_A11G2836 (RPPL1) within the chromosome 11 QTL region, andGh_D02G0257 (RLP12) and Gh_D02G0259 (RLP12) within the chromosome 14 QTL region.

CONCLUSIONS

The findings of this study deepen our understanding of host-nematode interactions, identify candidate genes for downstream applications, and contribute to advancements in resistance breeding and sustainable nematode management strategies.

Insights into the Role of GhTAT2 Genes in Tyrosine Metabolism and Drought Stress Tolerance in Cotton

Gossypium hirsutum is a key fiber crop that is sensitive to environmental factors, particularly drought stress, which can reduce boll size, increase flower shedding, and impair photosynthesis. The aminotransferase (AT) gene is essential for abiotic stress tolerance. A total of 3 Gossypium species were analyzed via genome-wide analysis, and the results unveiled 103 genes in G. hirsutum, 47 in G. arboreum, and 53 in G. raimondii. Phylogenetic analysis, gene structure examination, motif analysis, subcellular localization prediction, and promoter analysis revealed that the GhAT genes can be classified into five main categories and play key roles in abiotic stress tolerance. Using RNA-seq expression and KEGG enrichment analysis of GhTAT2, a coexpression network was established, followed by RT-qPCR analysis to identify hub genes. The RT-qPCR results revealed that the genes Gh_A13G1261, Gh_D13G1562, Gh_D10G1155, Gh_A10G1320, and Gh_D06G1003 were significantly upregulated in the leaf and root samples following drought stress treatment, with Gh_A13G1261 identified as the hub gene. The GhTAT2 genes were considerably enriched for tyrosine, cysteine, methionine, and phenylalanine metabolism and isoquinoline alkaloid, tyrosine, tryptophan, tropane, piperidine, and pyridine alkaloid biosynthesis. Under drought stress, KEGG enrichment analysis manifested significant upregulation of amino acids such as L-DOPA, L-alanine, L-serine, L-homoserine, L-methionine, and L-cysteine, whereas metabolites such as maleic acid, p-coumaric acid, quinic acid, vanillin, and hyoscyamine were significantly downregulated. Silencing the GhTAT2 gene significantly affected the shoot and root fresh weights of the plants compared with those of the wild-type plants under drought conditions. RT-qPCR analysis revealed that GhTAT2 expression in VIGS-treated seedlings was lower than that in both wild-type and positive control plants, indicating that silencing GhTAT2 increases sensitivity to drought stress. In summary, this thorough analysis of the gene family lays the groundwork for a detailed study of the GhTAT2 gene members, with a specific focus on their roles and contributions to drought stress tolerance.

Identification of UDP-glucosyltransferase involved in the biosynthesis of phloridzin in Gossypium hirsutum

Phloridzin has various functions, including antioxidant properties and the treatment of diabetes, and has long been used in pharmaceutical and physiological research. The glycosylation of phloretin is a key step in the biosynthesis of phloridzin. In this study, a genome-wide association study (GWAS) based on phloridzin content was applied, and the key gene GhUGT88F3 for phloridzin-specific biosynthesis was identified in cotton. A single-base deletion in GhUGT88F3 in haplotype I caused a frameshift mutation, leading to premature translation termination and a significant reduction in phloridzin content. Molecular docking revealed important amino acid residues for GhUGT88F3's UDP-glucose transfer activity. Additionally, the transcription factor GhMYB330 was found to positively regulate GhUGT88F3 expression through population transcriptome analysis and LUC experiment. Moreover, phloridzin content was significantly elevated in both GhUGT88F3 and GhMYB330 overexpression transgenic plants. This study expands the diversity of UDP-glucosyltransferases in plants and offers a potential strategy for the sustainable production of bioactive compounds with therapeutic potential.

Comprehensive analysis of amino acid/auxin permease family genes reveal the positive role of GhAAAP128 in cotton tolerance to cold stress

Amino acid/auxin permeases (AAAPs) play crucial roles in plant development and response to environmental stimuli. They have been characterized at genome-wide levels in several plant species. However, little is known about the AAAP genes in Gossypium. Here, we identified 149, 141, 73, and 70 AAAPs from G. hirsutum, G. barbadense, G. arboreum, and G. raimondii, respectively. All the AAAPs were categorized into eight subfamilies (Groups I-VIII). Moreover, we found that 182 and 179 AAAP paralogous gene pairs existed within G. hirsutum and G. barbadense genomes, respectively, and whole genome duplication (WGD) or segmental duplication contributed to the expansion of these AAAPs during evolution. Additionally, many cis-elements related to abiotic stress responses were detected in the promoter regions of GhAAAPs and GbAAAPs. Consistently, the expression of multiple AAAPs was significantly induced by NaCl, polyethylene glycol 6000, and especially cold stress. Among these GhAAAPs, GhAAAP128 had clearly positive roles in cotton and Arabidopsis seedling tolerance to cold stress. It may improve plant cold tolerance by up-regulating the expression of some anthocyanin synthesis genes rather than CBF (C-repeat binding factor) signaling genes. Our findings provide important information for further functional analysis of GhAAAPs in response to stressful cues, particularly cold stress in cotton plants.

GhRAP2.4 enhances drought tolerance by positively regulating the strigolactone receptor GhD14 expression in cotton (Gossypium hirsutum L.)

Drought poses significant challenges to crop productivity, necessitating a deeper understanding of plant adaptive mechanisms. Strigolactones (SLs), a class of phytohormones, have been recognized as crucial regulators in plant responses to drought, yet the specific role of SL receptor in drought tolerance in cotton (Gossypium hirsutum L.) remains underexplored. In this study, we identified and characterized DWARF14 (GhD14), a SL receptor in cotton. Silencing GhD14 in cotton compromised drought tolerance by reducing leaf relative water content and chlorophyll content, slowing stomatal closure, increasing reactive oxygen species levels, and decreasing antioxidant enzyme activities. Conversely, overexpression of GhD14 in Arabidopsis d14 mutants rescued their drought-sensitive phenotype. Further, we identified a 197-bp fragment (-697 to -894 bp) in the GhD14 promoter that plays a crucial role in the drought stress response. RELATED TO APETALA 2.4 (GhRAP2.4), a dehydration responsive element binding protein (DREB) transcription factor, binds directly to the GhD14 promoter, enhancing its transcription under drought conditions. Silencing GhRAP2.4 in cotton resulted in reduced drought tolerance. This study not only elucidates the molecular interplay between GhRAP2.4 and GhD14 in cotton's drought response but also provides a potential target for genetic modification to improve drought resilience in crops.

Exploring the differences in traits and genes between brown cotton and white cotton hybrid offspring (Gossypium hirsutum L.)

Brown cotton and white cotton are two important raw materials used in the cotton fiber industry. Clarifying the differences in morphology, agronomic traits, and fiber pigments between these varieties can facilitate the implementation of corresponding cultivation and breeding techniques. Therefore, we obtained F2 generation brown cotton plants through hybridization and compared them with their parents. In terms of agronomic traits, plant morphology and leaf shape were similar, but brown cotton presented more villi on the main stem. The first fruiting branch node was within the range of 4-6 cm, and the first fruiting branch node height was greater than that of TM-1, i.e., between 13.25 cm and 22.79 cm, with no difference compared with that of P26. The plant height was greater than that of the parents, and the number of bolls was essentially the same as that in TM-1 and greater than that in P26. The lint percentage and average fiber length were lower in TM-1 than in P26, and the seed index was greater than that in TM-1 and P26. Pigment measurements revealed that the chlorophyll a content in brown cotton during the boll stage was lower than that in white cotton, and the content of proanthocyanidin in the cotton fibers was greater in brown cotton than in white cotton. At 15 days after pollination, the highest content was 159.8 mg/g. To determine the differences in gene expression levels, we conducted transcriptome sequencing. Gene Ontology (GO) analysis revealed that the differentially expressed genes (DEGs) were enriched in pathways related to the cell wall and enzyme activity, whereas Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that the DEGs were enriched in flavonoid synthesis pathways. Transcription factor analysis revealed that the expression of the MYB3 transcription factor (Ghir_D07G002110) was higher in brown cotton, and bioinformatics analysis revealed that this gene has regulatory effects on the CHS, CHI1, and F3H genes.

Identification of the MAP4K gene family reveals GhMAP4K13 regulates drought and salt stress tolerance in cotton

Mitogen-activated protein kinase kinase kinase kinases (MAP4Ks) are a class of highly conserved serine/threonine-protein kinases in eukaryotes. They participate in the typical MAPK cascade system and various signal transduction pathways regulating biological processes in plants, during stressful conditions. To date, genome-wide identification of MAP4Ks in cotton has not been reported. In this study, 77 MAP4K genes were identified in four Gossypium species. Protein characteristics, gene structures, conserved motifs and gene expression analysis were carried out. Genome-wide or fragment duplication has played an important role in the expansion of the GhMAP4K. Promoter cis-acting elements and expression patterns indicated that GhMAP4Ks are related to plant hormones (ABA, MeJA, GA, IAA, SA) and various stresses (drought, hypothermia and wound). Overexpressing GhMAP4K13 in Arabidopsis showed higher stem length in response to drought and salt stress. The wilting degree in virus-induced GhMAP4K13 gene silenced plants was substantially greater than wild type plants under drought and salt stress. Transcriptomic analysis showed that most differentially expressed genes were involved in the MAPK signaling pathway, carbon metabolism and porphyrin metabolism. Additionally, transgenic Arabidopsis and VIGS cotton showed that GhMAP4K13 was positively responsive to drought and salt stresses. This study will play an important role in understanding the function of the MAP4K gene family in response to abiotic stress in cotton.

A GWAS identified loci and candidate genes associated with fiber quality traits in a new cotton MAGIC population

KEY MESSAGE

GWAS of a new MAGIC population containing alleles from five tetraploid Gossypium species identified novel fiber QTL and confirmed previously identified stable QTL. Identification of loci and underlying genes for fiber quality traits will facilitate genetic improvement in cotton fiber quality. In this research, a genome-wide association study (GWAS) was carried out for fiber quality attributes using a new multi-parent advanced generation inter-cross (MAGIC) population consisting of 372 recombinant inbred lines (RILs). Sixteen parents including 12 exotic germplasm lines derived from five tetraploid Gossypium species and 4 Upland cotton varieties were intercrossed to develop the population. Both RILs and parental lines were evaluated at three locations, College Station, Texas; Las Cruses, New Mexico; and Stoneville, Mississippi, from 2016 through 2023. Fiber length (UHM) had positive correlation with strength (STR) and length uniformity (UNI) and a negative correlation with micronaire (MIC) and elongation (ELO). By combining all the data from all locations, we identified significant SNPs for ELO, UHM, and UNI while STR and MIC were location dependent. These results suggest an important role of genotype by environment interaction in a GWAS of fiber traits. Twenty possible novel fiber QTL were identified: 10 for STR, three for UNI, and seven for MIC. The QTL for ELO (Chr.D04: 53-Mb), UHM (Chr.D11: 24-Mb), and UNI (Chr.D04: 34-Mb) were stable across multiple environments and may be useful for marker-assisted selection to improve fiber quality. For STR, we found candidate genes Gh_A07G1574 and Gh_A07G1581 to be present in the previously identified QTL region (Chr.A07: 77-Mb) on chromosome A07. Identified loci and their corresponding candidate genes will be useful to improve fiber quality via marker-assisted selection in a cotton breeding.

Disrupted oxylipin biosynthesis mitigates pathogen infections and pest infestations in cotton (Gossypium hirsutum)

Cotton (Gossypium hirsutum) is the world's most important fiber crop, critical to global textile industries and agricultural economies. However, cotton yield and harvest quality are undermined by the challenges introduced from invading pathogens and pests. Plant-synthesized oxylipins, specifically 9-hydroxy fatty acids resulting from 9-lipoxygenase activity (9-LOX), enhance the growth and development of many microbes and pests. We hypothesized that targeted disruption of 9-LOX-encoding genes in cotton could bolster crop resilience against prominent agronomic threats. Fusarium oxysporum f. sp. vasinfectum (FOV), Aphis gossypii (cotton aphid), and tobacco rattle virus induced the expression of 9-oxylipin biosynthesis genes, suggesting that the 9-LOX gene products were susceptibility factors to these stressors. Transiently disrupting the expression of the 9-LOX-encoding genes by virus-induced gene silencing significantly reduced target transcript accumulation, and this correlated with impaired progression of FOV infections and a significant decrease in the fecundity of cotton aphids. These findings emphasize that the cotton 9-LOX-derived oxylipins are leveraged by multiple pathogens and pests to enhance their virulence in cotton, and reducing the expression of 9-LOX-encoding genes can benefit cotton crop vitality.

Histone deacetylase GhHDA5 negatively regulates Verticillium wilt resistance in cotton

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

GhLCYε-3 characterized as a lycopene cyclase gene responding to drought stress in cotton

Drought stress significantly affects crop productivity. Carotenoids are essential photosynthetic pigment for plants, bacteria, and algae, with signaling and antioxidant functions. Lutein is a crucial branch product in the carotenoid synthesis pathway, which effectively improves the stress tolerance of higher plants. lycopene cyclase, a central enzyme for lutein synthesis, holds great significance in regulating lutein production. This research establishes a correlation between lutein content and stress resistance by measuring the drought resistance and lutein content of various cotton materials. To identify which crucial genes are associated with lutein, the lycopene cyclase family (LCYs) was analyzed. The research found that LCYs form a highly conserved family divided into two subfamilies, LCY-ε (lycopene ε-cyclase) and LCY-β (lycopene β-cyclase). Most members of the LCY family contain photoresponsive elements and abscisic acid elements. qRT-PCR demonstrates showed that most genes responded positively to drought stress, and GhLCYε-3 was expressed significantly differently under drought stress. Virus-induced gene silencing (VIGS) assay showed that the content of GhLCYε-3 was significantly increased with MDA and PRO, and the contents of chlorophyll and lutein were significantly decreased in pYL156 plants. The decrease in GhLCYε-3 expression is speculated to lead to reduced lutein content in vivo, resulting in the accumulation of reactive oxygen species (ROS) and decreased drought tolerance. This research enriched the understanding of LCY gene family and lutein function, and provided a new reference for cotton planting in arid areas.

Synopsis

Lycopene cyclase plays an important role in enhancing the ability of scavenging ROS and drought resistance of plants.

Integrating physiological and transcriptomic analyses explored the regulatory mechanism of cold tolerance at seedling emergence stage in upland cotton (Gossypium hirsutum L.)

Cold stress is one of the major abiotic stressor that profoundly impacts plant growth. Cotton, a widely cultivated variety, is particularly susceptible to cold stress. Unraveling the responses to cold stress is critical for cotton demand. In this investigation, we conducted comparative physiological and transcriptomic analyses of the cold-tolerant variety XLZ16 and cold-sensitive variety XLZ84 at seedling emergence stage under cold stress. Following exposure to cold stress, XLZ16 exhibited a markedly higher growth phenotype and increased activity of antioxidant enzymes, while simultaneously showing reduced cellular oxidative damage and apoptosis. Furthermore, the levels of auxin (IAA), cytokinin (CTK), and salicylic acid (SA) significantly increased during cold stress, whereas the contents of catendorsterol (TY), brassinosterone (CS), and jasmonic acid (JA) significantly decreased. Integrated with stoichiometric analysis, these findings definitively demonstrated significant differences in antioxidant capacity and hormone content between the two varieties during their response to cold stress. A total of 6207 potential cold-responsive differentially expressed genes (DEGs) were identified through transcriptome sequencing analysis. Enrichment analyses of these DEGs revealed that pathways related to "hormones biosynthesis and signaling" as well as "circadian rhythm" were associated with cold response. Notably, the hub gene Gh_D12G2567 (GhJAZ3), encoding jasmonate ZIM-domain (JAZ) proteins, was found to influence the JA signal transduction pathway and regulate cotton growth under cold stress within the MEred module network. Furthermore, suppressing the expression level of GhJAZ3 by virus-induced gene silencing led to the reduction of cold resistance, implying GhJAZ3 as a positive regulator of cold tolerance. This study provides valuable insights into the response mechanisms of cotton under cold stress. It also serves as a reference and foundation for further enhancing cold tolerance of new cotton varieties.

Membrane Interactions of GET1 and GET2 Facilitate Fiber Cell Initiation through the Guided Entry of the TA Protein Pathway in Cotton

The guided entry of TA proteins (GET) pathway, which is responsible for the post-translational targeting and insertion of the tail-anchored (TA) protein into the endoplasmic reticulum (ER), plays an important role in physiological processes such as protein sorting, vesicle trafficking, cell apoptosis, and enzymatic reactions in which the GET1/2 complex is indispensable. However, a comprehensive study of the GET1 and GET2 genes and the GET pathway in cotton has not yet been carried out. Here, 12 GET1 and 21 GET2 genes were identified in nine representative plant species, and the phylogenetic relationships, gene structures, protein motifs, cis-regulatory elements (CREs), and temporal and spatial expression profiles were analyzed thoroughly. Our study indicated that GhGET1s and GhGET2s might be localized on ER membranes. According to expression profiling and CREs analysis, GhGET2-A02 was identified as a promising candidate for fiber cell development, interacting with two GhGET1s in the membrane, with a binding bias toward GhGET1-A06. Silencing of GhGET1-A06 or GhGET2-A02 reduced fiber initiation and elongation. In summary, our research provides important evidence for understanding the gene families and functions of GET1 and GET2 in cotton and provides clues for molecular breeding of high-quality cotton fiber varieties.

Natural variation at the cotton HIC locus increases trichome density and enhances resistance to aphids

Plant trichomes are an excellent model for studying cell differentiation and development, providing crucial defenses against biotic and abiotic stresses. There is a well-established inverse relationship between trichome density and aphid prevalence, indicating that higher trichome density leads to reduced aphid infestations. Here we present the cloning and characterization of a dominant quantitative trait locus, HIC (hirsute cotton), which significantly enhances cotton trichome density. This enhancement leads to markedly improved resistance against cotton aphids. The HIC encodes an HD-ZIP IV transcriptional activator, crucial for trichome initiation. Overexpression of HIC leads to a substantial increase in trichome density, while knockdown of HIC results in a marked decrease in density, confirming its role in trichome regulation. We identified a variant in the HIC promoter (-810 bp A to C) that increases transcription of HIC and trichome density in hirsute cotton compared with Gossypium hirsutum cultivars with fewer or no trichomes. Interestingly, although the -810 variant in the HIC promoter is the same in G. barbadense and hirsute cotton, the presence of a copia-like retrotransposon insertion in the coding region of HIC in G. barbadense causes premature transcription termination. Further analysis revealed that HIC positively regulates trichome density by directly targeting the EXPANSIN A2 gene, which is involved in cell wall development. Taken together, our results underscore the pivotal function of HIC as a primary regulator during the initial phases of trichome formation, and its prospective utility in enhancing aphid resistance in superior cotton cultivars via selective breeding.

Genome-Wide Analysis of Caffeoyl-CoA-O-methyltransferase (CCoAOMT) Family Genes and the Roles of GhCCoAOMT7 in Lignin Synthesis in Cotton

Caffeoyl coenzyme A-O-methyltransferase (CCoAOMT) has a critical function in the lignin biosynthesis pathway. However, its functions in cotton are not clear. In this research, we observed 50 CCoAOMT genes from four cotton species, including two diploids (Gossypium arboretum, 9, and Gossypium raimondii, 8) and two tetraploids (Gossypium hirsutum, 16, and Gossypium barbadense, 17), performed bioinformatic analysis, and focused on the involvement and functions of GhCCoAOMT7 in lignin synthesis of Gossypium hirsutum. CCoAOMT proteins were divided into four subgroups based on the phylogenetic tree analysis. Motif analysis revealed that all CCoAOMT proteins possess conserved Methyltransf_3 domains, and conserved structural features were identified based on the genes' exon-intron organization. A synteny analysis suggested that segmental duplications were the primary cause in the expansion of the CCoAOMT genes family. Transcriptomic data analysis of GhCCoAOMTs revealed that GhCCoAOMT2, GhCCoAOMT7, and GhCCoAOMT14 were highly expressed in stems. Subcellular localization experiments of GhCCoAOMT2, GhCCoAOMT7, and GhCCoAOMT14 showed that GhCCoAOMT2, GhCCoAOMT7, and GhCCoAOMT14 were localized in the nucleus and plasma membrane. However, there are no cis-regulatory elements related to lignin synthesis in the GhCCoAOMT7 gene promoter. GhCCoAOMT7 expression was inhibited by virus-induced gene silencing technology to obtain gene silencing lines, the suppression of GhCCoAOMT7 expression resulted in a 56% reduction in the lignin content in cotton stems, and the phloroglucinol staining area corresponding to the xylem was significantly decreased, indicating that GhCCoAOMT7 positively regulates lignin synthesis. Our results provided fundamental information regarding CCoAOMTs and highlighted their potential functions in cotton lignin biosynthesis and lignification.

Characterization and expression analysis of the MADS-box gene AGL8 in cotton: insights into gene function differentiation in plant growth and stress resistance

BACKGROUND

AGAMOUS-LIKE 8 (AGL8) belongs to the MADS-box family, which plays important roles in transcriptional regulation, sequence-specific DNA binding and other biological processes and molecular functions. The genome of cotton, a representative polyploid plant, contains multiple AGL8 genes. However, their functional differentiation is still unclear.

METHODS AND RESULTS

In this study, a comprehensive genomic analysis of AGL8 genes was conducted. Cotton AGL8s were subdivided into four subgroups (Groups 1, 2, 3, and 4) based on phylogenetic analysis, and different subgroups of AGL8s presented different characteristics, including different structures and conserved motifs. With respect to the promoter regions of the GhAGL8 genes, we successfully predicted cis-elements that respond to phytohormone signal transduction and the stress response of plants. Transcriptome data and real-time quantitative PCR validation indicated that three genes, namely, GH_D07G0744, GH_A03G0856 and GH_A07G0749, were highly induced by methyl jasmonate (MeJA), salicylic acid (SA), and abscisic acid (ABA), which indicated that they function in plant resistance to abiotic and biotic stresses.

CONCLUSIONS

The information from the gene structure, number and types of conserved domains, tissue-specific expression levels, and expression patterns under different treatments highlights the differences in sequence and function of the cotton AGL8 genes. Different AGL8s play roles in vegetative growth, reproductive development, and plant stress resistance. These results lay a foundation for further study of GhAGL8s in cotton.

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.

Characterization, Evolution, Expression and Functional Divergence of the DMP Gene Family in Plants

The DMP (DOMAIN OF UNKNOWN FUNCTION 679 membrane protein) domain, containing a family of membrane proteins specific to green plants, is involved in numerous biological functions including physiological processes, reproductive development and senescence in Arabidopsis, but their evolutionary relationship and biological function in most crops remains unknown. In this study, we scrutinized phylogenetic relationships, gene structure, conserved domains and motifs, promoter regions, gene loss/duplication events and expression patterns. Overall, 240 DMPs were identified and analyzed in 24 plant species selected from lower plants to angiosperms. Comprehensive evolutionary analysis revealed that these DMPs underwent purifying selection and could be divided into five groups (I-V). DMP gene structure showed that it may have undergone an intron loss event during evolution. The five DMP groups had the same domains, which were distinct from each other in terms of the number of DMPs; group III was the largest, closely followed by group V. The DMP promotor region with various cis-regulatory elements was predicted to have a potential role in development, hormone induction and abiotic stresses. Based on transcriptomic data, expression profiling revealed that DMPs were primarily expressed in reproductive organs and were moderately expressed in other tissues. Evolutionary analysis suggested that gene loss events occurred more frequently than gene duplication events among all groups. Overall, this genome-wide study elucidates the potential function of the DMP gene family in selected plant species, but further research is needed in many crops to validate their biological roles.

QTL Mapping of Fiber- and Seed-Related Traits in Chromosome Segment Substitution Lines Derived from Gossypium hirsutum × Gossypium darwinii

A narrow genetic basis limits further the improvement of modern Gossypium hirsutum cultivar. The abundant genetic diversity of wild species provides available resources to solve this dilemma. In the present study, a chromosome segment substitution line (CSSL) population including 553 individuals was established using G. darwinii accession 5-7 as the donor parent and G. hirsutum cultivar CCRI35 as the recipient parent. After constructing a high-density genetic map with the BC1 population, the genotype and phenotype of the CSSL population were investigated. A total of 235 QTLs, including 104 QTLs for fiber-related traits and 132 QTLs for seed-related traits, were identified from four environments. Among these QTLs, twenty-seven QTLs were identified in two or more environments, and twenty-five QTL clusters consisted of 114 QTLs. Moreover, we identified three candidate genes for three stable QTLs, including GH_A01G1096 (ARF5) and GH_A10G0141 (PDF2) for lint percentage, and GH_D01G0047 (KCS4) for seed index or oil content. These results pave way for understanding the molecular regulatory mechanism of fiber and seed development and would provide valuable information for marker-assisted genetic improvement in cotton.

Genome-wide association study of fiber quality traits in US upland cotton (Gossypium hirsutum L.)

KEY MESSAGE

A GWAS in an elite diversity panel, evaluated across 10 environments, identified genomic regions regulating six fiber quality traits, facilitating genomics-assisted breeding and gene discovery in upland cotton. In this study, an elite diversity panel of 348 upland cotton accessions was evaluated in 10 environments across the US Cotton Belt and genotyped with the cottonSNP63K array, for a genome-wide association study of six fiber quality traits. All fiber quality traits, upper half mean length (UHML: mm), fiber strength (FS: g tex-1), fiber uniformity (FU: %), fiber elongation (FE: %), micronaire (MIC) and short fiber content (SFC: %), showed high broad-sense heritability (> 60%). All traits except FE showed high genomic heritability. UHML, FS and FU were all positively correlated with each other and negatively correlated with FE, MIC and SFC. GWAS of these six traits identified 380 significant marker-trait associations (MTAs) including 143 MTAs on 30 genomic regions. These 30 genomic regions included MTAs identified in at least three environments, and 23 of them were novel associations. Phenotypic variation explained for the MTAs in these 30 genomic regions ranged from 6.68 to 11.42%. Most of the fiber quality-associated genomic regions were mapped in the D-subgenome. Further, this study confirmed the pleiotropic region on chromosome D11 (UHML, FS and FU) and identified novel co-localized regions on D04 (FU, SFC), D05 (UHML, FU, and D06 UHML, FU). Marker haplotype analysis identified superior combinations of fiber quality-associated genomic regions with high trait values (UHML = 32.34 mm; FS = 32.73 g tex-1; FE = 6.75%). Genomic analyses of traits, haplotype combinations and candidate gene information described in the current study could help leverage genetic diversity for targeted genetic improvement and gene discovery for fiber quality traits in cotton.

GhJUB1_3-At positively regulate drought and salt stress tolerance under control of GhHB7, GhRAP2-3 and GhRAV1 in Cotton

Climate change severely affects crop production. Cotton is one of the primary fiber crops in the world and its production is susceptible to various environmental stresses, especially drought and salinity. Development of stress tolerant genotypes is the only way to escape from these environmental constraints. We identified sixteen homologs of the Arabidopsis JUB1 gene in cotton. Expression of GhJUB1_3-At was significantly induced in the temporal expression analysis of GhJUB1 genes in the roots of drought tolerant (H177) and susceptible (S9612) cotton genotypes under drought. The silencing of the GhJUB1_3-At gene alone and together with its paralogue GhJUB1_3-Dt reduced the drought tolerance in cotton plants. The transgenic lines exhibited tolerance to the drought and salt stress as compared to the wildtype (WT). The chlorophyll and relative water contents of wildtype decreased under drought as compared to the transgenic lines. The transgenic lines showed decreased H2O2 and increased proline levels under drought and salt stress, as compared to the WT, indicating that the transgenic lines have drought and salt stress tolerance. The expression analysis of the transgenic lines and WT revealed that GAI was upregulated in the transgenic lines in normal conditions as compared to the WT. Under drought and salt treatment, RAB18 and RD29A were strongly upregulated in the transgenic lines as compared to the WT. Conclusively, GhJUB1_3-At is not an auto activator and it is regulated by the crosstalk of GhHB7, GhRAP2-3 and GhRAV1. GhRAV1, a negative regulator of abiotic stress tolerance and positive regulator of leaf senescence, suppresses the expression of GhJUB1_3-At under severe circumstances leading to plant death.

Identification of cotton PIP5K genes and role of GhPIP5K9a in primary root development

Phosphatidylinositol 4 phosphate 5-kinase (PIP5K) is crucial for the phosphatidylinositol (PI) signaling pathway. It plays a significant role in plant growth and development, as well as stress response. However, its effects on cotton are unknown. This study identified PIP5K genes from four cotton species and conducted bioinformatic analyses, with a particular emphasis on the functions of GhPIP5K9a in primary roots. The results showed that cotton PIP5Ks were classified into four subgroups. Analysis of gene structure and motif composition showed obvious conservation within each subgroup. Synteny analysis suggested that the PIP5K gene family experienced significant expansion due to both whole-genome duplication (WGD) and segmental duplication. Transcriptomic data analysis revealed that the majority of GhPIP5K genes had the either low or undetectable levels of expression. Moreover, GhPIP5K9a is highly expressed in the root and was located in plasmalemma. Suppression of GhPIP5K9a transcripts resulted in longer primary roots, longer primary root cells and increased auxin polar transport-related genes expression, and decreased abscisic acid (ABA) content, indicating that GhPIP5K9a negatively regulates cotton primary root growth. This study lays the foundation for further exploration of the role of the PIP5K genes in cotton.

GhHDZ76, a cotton HD-Zip transcription factor, involved in regulating the initiation and early elongation of cotton fiber development in G. hirsutum

In this study, the whole HD-Zip family members of G. hirsutum were identified, and GhHDZ76 was classified into the HD-Zip IV subgroup. GhHDZ76 was predominantly expressed in the 0-5 DPA of fiber development stage and localized in the nucleus. Overexpression of GhHDZ76 significantly increased the length and density of trichomes in Arabidopsis thaliana. The fiber length of GhHDZ76 knockout lines by CRISPR/Cas9 was significantly shorter than WT at the early elongation and mature stage, indicating that GhHDZ76 positively regulate the fiber elongation. Scanning electron microscopy showed that the number of ovule surface protrusion of 0 DPA of GhHDZ76 knockout lines was significantly lower than WT, suggesting that GhHDZ76 can also promote the initiation of fiber development. The transcript level of GhWRKY16, GhRDL1, GhEXPA1 and GhMYB25 genes related to fiber initiation and elongation in GhHDZ76 knockout lines were significantly decreased. Yeast two-hybrid and Luciferase complementation imaging (LCI) assays showed that GhHDZ76 can interact with GhWRKY16 directly. As a transcription factor, GhHDZ76 has transcriptional activation activity, which could bind to L1-box elements of the promoters of GhRDL1 and GhEXPA1. Double luciferase reporter assay showed that the GhWRKY16 could enhance the transcriptional activity of GhHDZ76 to pGhRDL1, but it did not promote the transcriptional activity of GhHDZ76 to pGhEXPA1. GhHDZ76 protein may also promote the transcriptional activity of GhWRKY16 to the downstream target gene GhMYB25. Our results provided a new gene resource for fiber development and a theoretical basis for the genetic improvement of cotton fiber quality.

Integrative Transcriptomic and Metabolic Analyses Reveal That Flavonoid Biosynthesis Is the Key Pathway Regulating Pigment Deposition in Naturally Brown Cotton Fibers

Brown cotton is a major cultivar of naturally colored cotton, and brown cotton fibers (BCFs) are widely utilized as raw materials for textile industry production due to their advantages of being green and dyeing-pollution-free. However, the mechanisms underlying the pigmentation in fibers are still poorly understood, which significantly limits their extensive applications in related fields. In this study, we conducted a multidimensional comparative analysis of the transcriptomes and metabolomes between brown and white fibers at different developmental periods to identify the key genes and pathways regulating the pigment deposition. The transcriptomic results indicated that the pathways of flavonoid biosynthesis and phenylpropanoid biosynthesis were significantly enriched regulatory pathways, especially in the late development periods of fiber pigmentation; furthermore, the genes distributed in the pathways of PAL, CHS, F3H, DFR, ANR, and UFGT were identified as significantly up-regulated genes. The metabolic results showed that six metabolites, namely (-)-Epigallocatechin, Apiin, Cyanidin-3-O-glucoside, Gallocatechin, Myricetin, and Poncirin, were significantly accumulated in brown fibers but not in white fibers. Integrative analysis of the transcriptomic and metabolomic data demonstrated a possible regulatory network potentially regulating the pigment deposition, in which three MYB transcription factors promote the expression levels of flavonoid biosynthesis genes, thereby inducing the content increase in (-)-Epigallocatechin, Cyanidin-3-O-glucoside, Gallocatechin, and Myricetin in BCFs. Our findings provide new insights into the pigment deposition mechanism in BCFs and offer references for genetic engineering and breeding of colored cotton materials.

Genome-Wide Identification of the Alfin-like Gene Family in Cotton (Gossypium hirsutum) and the GhAL19 Gene Negatively Regulated Drought and Salt Tolerance

Alfin-like (AL) is a small plant-specific gene family characterized by a PHD-finger-like structural domain at the C-terminus and a DUF3594 structural domain at the N-terminus, and these genes play prominent roles in plant development and abiotic stress response. In this study, we conducted genome-wide identification and analyzed the AL protein family in Gossypium hirsutum cv. NDM8 to assess their response to various abiotic stresses for the first time. A total of 26 AL genes were identified in NDM8 and classified into four groups based on a phylogenetic tree. Moreover, cis-acting element analysis revealed that multiple phytohormone response and abiotic stress response elements were highly prevalent in AL gene promoters. Further, we discovered that the GhAL19 gene could negatively regulate drought and salt stresses via physiological and biochemical changes, gene expression, and the VIGS assay. The study found there was a significant increase in POD and SOD activity, as well as a significant change in MDA in VIGS-NaCl and VIGS-PEG plants. Transcriptome analysis demonstrated that the expression levels of the ABA biosynthesis gene (GhNCED1), signaling genes (GhABI1, GhABI2, and GhABI5), responsive genes (GhCOR47, GhRD22, and GhERFs), and the stress-related marker gene GhLEA14 were regulated in VIGS lines under drought and NaCl treatment. In summary, GhAL19 as an AL TF may negatively regulate tolerance to drought and salt by regulating the antioxidant capacity and ABA-mediated pathway.

Genome-Wide Identification of the WRKY Gene Family in Four Cotton Varieties and the Positive Role of GhWRKY31 in Response to Salt and Drought Stress

The WRKY gene family is ubiquitously distributed in plants, serving crucial functions in stress responses. Nevertheless, the structural organization and evolutionary dynamics of WRKY genes in cotton have not been fully elucidated. In this study, a total of 112, 119, 217, and 222 WRKY genes were identified in Gossypium arboreum, Gossypium raimondii, Gossypium hirsutum, and Gossypium barbadense, respectively. These 670 WRKY genes were categorized into seven distinct subgroups and unequally distributed across chromosomes. Examination of conserved motifs, domains, cis-acting elements, and gene architecture collectively highlighted the evolutionary conservation and divergence within the WRKY gene family in cotton. Analysis of synteny and collinearity further confirmed instances of expansion, duplication, and loss events among WRKY genes during cotton evolution. Furthermore, GhWRKY31 transgenic Arabidopsis exhibited heightened germination rates and longer root lengths under drought and salt stress. Silencing GhWRKY31 in cotton led to reduced levels of ABA, proline, POD, and SOD, along with downregulated expression of stress-responsive genes. Yeast one-hybrid and molecular docking assays confirmed the binding capacity of GhWRKY31 to the W box of GhABF1, GhDREB2, and GhRD29. The findings collectively offer a systematic and comprehensive insight into the evolutionary patterns of cotton WRKYs, proposing a suitable regulatory framework for developing cotton cultivars with enhanced resilience to drought and salinity stress.

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.

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 β, 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.

Decoding drought resilience: a comprehensive exploration of the cotton Eceriferum (CER) gene family and its role in stress adaptation

BACKGROUND

The cuticular wax serves as a primary barrier that protects plants from environmental stresses. The Eceriferum (CER) gene family is associated with wax production and stress resistance.

RESULTS

In a genome-wide identification study, a total of 52 members of the CER family were discovered in four Gossypium species: G. arboreum, G. barbadense, G. raimondii, and G. hirsutum. There were variations in the physicochemical characteristics of the Gossypium CER (GCER) proteins. Evolutionary analysis classified the identified GCERs into five groups, with purifying selection emerging as the primary evolutionary force. Gene structure analysis revealed that the number of conserved motifs ranged from 1 to 15, and the number of exons varied from 3 to 13. Closely related GCERs exhibited similar conserved motifs and gene structures. Analyses of chromosomal positions, selection pressure, and collinearity revealed numerous fragment duplications in the GCER genes. Additionally, nine putative ghr-miRNAs targeting seven G. hirsutum CER (GhCER) genes were identified. Among them, three miRNAs, including ghr-miR394, ghr-miR414d, and ghr-miR414f, targeted GhCER09A, representing the most targeted gene. The prediction of transcription factors (TFs) and the visualization of the regulatory TF network revealed interactions with GhCER genes involving ERF, MYB, Dof, bHLH, and bZIP. Analysis of cis-regulatory elements suggests potential associations between the CER gene family of cotton and responses to abiotic stress, light, and other biological processes. Enrichment analysis demonstrated a robust correlation between GhCER genes and pathways associated with cutin biosynthesis, fatty acid biosynthesis, wax production, and stress response. Localization analysis showed that most GCER proteins are localized in the plasma membrane. Transcriptome and quantitative reverse transcription-polymerase chain reaction (qRT-PCR) expression assessments demonstrated that several GhCER genes, including GhCER15D, GhCER04A, GhCER06A, and GhCER12D, exhibited elevated expression levels in response to water deficiency stress compared to control conditions. The functional identification through virus-induced gene silencing (VIGS) highlighted the pivotal role of the GhCER04A gene in enhancing drought resistance by promoting increased tissue water retention.

CONCLUSIONS

This investigation not only provides valuable evidence but also offers novel insights that contribute to a deeper understanding of the roles of GhCER genes in cotton, their role in adaptation to drought and other abiotic stress and their potential applications for cotton improvement.

Comparative analysis, diversification, and functional validation of plant nucleotide-binding site domain genes

Nucleotide-binding site (NBS) domain genes are one of the superfamily of resistance genes involved in plant responses to pathogens. The current study identified 12,820 NBS-domain-containing genes across 34 species covering from mosses to monocots and dicots. These identified genes are classified into 168 classes with several novel domain architecture patterns encompassing significant diversity among plant species. Several classical (NBS, NBS-LRR, TIR-NBS, TIR-NBS-LRR, etc.) and species-specific structural patterns (TIR-NBS-TIR-Cupin_1-Cupin_1, TIR-NBS-Prenyltransf, Sugar_tr-NBS etc.) were discovered. We observed 603 orthogroups (OGs) with some core (most common orthogroups; OG0, OG1, OG2, etc.) and unique (highly specific to species; OG80, OG82, etc.) OGs with tandem duplications. The expression profiling presented the putative upregulation of OG2, OG6, and OG15 in different tissues under various biotic and abiotic stresses in susceptible and tolerant plants to cotton leaf curl disease (CLCuD). The genetic variation between susceptible (Coker 312) and tolerant (Mac7) Gossypium hirsutum accessions identified several unique variants in NBS genes of Mac7 (6583 variants) and Coker312 (5173 variants). The protein-ligand and proteins-protein interaction showed a strong interaction of some putative NBS proteins with ADP/ATP and different core proteins of the cotton leaf curl disease virus. The silencing of GaNBS (OG2) in resistant cotton through virus-induced gene silencing (VIGS) demonstrated its putative role in virus tittering. The presented study will be further helpful in understanding the plant adaptation mechanism.

Genome-wide identification and analysis of the cotton ALDH gene family

BACKGROUND

Aldehyde dehydrogenases (ALDHs) are a family of enzymes that catalyze the oxidation of aldehyde molecules into the corresponding carboxylic acid, regulate the balance of aldehydes and protect plants from the poisoning caused by excessive accumulation of aldehydes; however, this gene family has rarely been studied in cotton.

RESULTS

In the present study, genome-wide identification was performed, and a total of 114 ALDH family members were found in three cotton species, Gossypium hirsutum, Gossypium arboreum and Gossypium raimondii. The ALDH genes were divided into six subgroups by evolutionary analysis. ALDH genes in the same subgroup showed similar gene structures and conserved motifs, but some genes showed significant differences, which may result in functional differences. Chromosomal location analysis and selective pressure analysis revealed that the ALDH gene family had experienced many fragment duplication events. Cis-acting element analysis revealed that this gene family may be involved in the response to various biotic and abiotic stresses. The RT‒qPCR results showed that the expression levels of some members of this gene family were significantly increased under salt stress conditions. Gohir.A11G040800 and Gohir.D06G046200 were subjected to virus-induced gene silencing (VIGS) experiments, and the sensitivity of the silenced plants to salt stress was significantly greater than that of the negative control plants, suggesting that Gohir.A11G040800 and Gohir.D06G046200 may be involved in the response of cotton to salt stress.

CONCLUSIONS

In total, 114 ALDH genes were identified in three Gossypium species by a series of bioinformatics analysis. Gene silencing of the ALDH genes of G. hirsutum revealed that ALDH plays an important role in the response of cotton to salt stress.

GhVIM28, a negative regulator identified from VIM family genes, positively responds to salt stress in cotton

The VIM (belonged to E3 ubiquitin ligase) gene family is crucial for plant growth, development, and stress responses, yet their role in salt stress remains unclear. We analyzed phylogenetic relationships, chromosomal localization, conserved motifs, gene structure, cis-acting elements, and gene expression patterns of the VIM gene family in four cotton varieties. Our findings reveal 29, 29, 17, and 14 members in Gossypium hirsutum (G.hirsutum), Gossypium barbadense (G.barbadense), Gossypium arboreum (G.arboreum), and Gossypium raimondii (G. raimondii), respectively, indicating the maturity and evolution of this gene family. motifs among GhVIMs genes were observed, along with the presence of stress-responsive, hormone-responsive, and growth-related elements in their promoter regions. Gene expression analysis showed varying patterns and tissue specificity of GhVIMs genes under abiotic stress. Silencing GhVIM28 via virus-induced gene silencing revealed its role as a salt-tolerant negative regulator. This work reveals a mechanism by which the VIM gene family in response to salt stress in cotton, identifying a potential negative regulator, GhVIM28, which could be targeted for enhancing salt tolerance in cotton. The objective of this study was to explore the evolutionary relationship of the VIM gene family and its potential function in salt stress tolerance, and provide important genetic resources for salt tolerance breeding of cotton.

GhTKPR1_8 functions to inhibit anther dehiscence and reduce pollen viability in cotton

Sporopollenin, as the main component of the pollen exine, is a highly resistant polymer that provides structural integrity under unfavourable environmental conditions. Tetraketone α-pyrone reductase 1 (TKPR1) is essential for sporopollenin formation, catalyzing the reduction of tetraketone carbonyl to hydroxylated α-pyrone. The functional role of TKPR1 in male sterility has been reported in flowering plants such as maize, rice, and Arabidopsis. However, the molecular cloning and functional characterization of TKPR1 in cotton remain unaddressed. In this study, we identified 68 TKPR1s from four cotton species, categorized into three clades. Transcriptomics and RT-qPCR demonstrated that GhTKPR1_8 exhibited typical expression patterns in the tetrad stage of the anther. GhTKPR1_8 was localized to the endoplasmic reticulum. Moreover, ABORTED MICROSPORES (GhAMS) transcriptionally activated GhTKPR1_8 as indicated by luciferase complementation tests. GhTKPR1_8-knockdown inhibited anther dehiscence and reduced pollen viability in cotton. Additionally, overexpression of GhTKPR1_8 in the attkpr1 mutant restored its male sterile phenotype. This study offers novel insights into the investigation of TKPR1 in cotton while providing genetic resources for studying male sterility.

Genome-Wide Identification of Calmodulin-Binding Protein 60 Gene Family and the Function of GhCBP60B in Cotton Growth and Development and Abiotic Stress Response

The calmodulin-binding protein 60 (CBP60) family is a gene family unique to plants, and its members play a crucial role in plant defense responses to pathogens and growth and development. Considering that cotton is the primary source of natural cotton textile fiber, the functional study of its CBP60 gene family members is critical. In this research, we successfully identified 162 CBP60 members from the genomes of 21 species. Of these, 72 members were found in four cotton species, divided into four clades. To understand the function of GhCBP60B in cotton in depth, we conducted a detailed analysis of its sequence, structure, cis-acting elements, and expression patterns. Research results show that GhCBP60B is located in the nucleus and plays a crucial role in cotton growth and development and response to salt and drought stress. After using VIGS (virus-induced gene silencing) technology to conduct gene silencing experiments, we found that the plants silenced by GhCBP60B showed dwarf plants and shortened stem nodes, and the expression of related immune genes also changed. In further abiotic stress treatment experiments, we found that GhCBP60B-silenced plants were more sensitive to drought and salt stress, and their POD (peroxidase) activity was also significantly reduced. These results imply the vital role of GhCBP60B in cotton, especially in regulating plant responses to drought and salt stress. This study systematically analyzed CBP60 gene family members through bioinformatics methods and explored in depth the biological function of GhCBP60B in cotton. These research results lay a solid foundation for the future use of the GhCBP60B gene to improve cotton plant type and its drought and salt resistance.

A Genome-Wide Analysis of the CEP Gene Family in Cotton and a Functional Study of GhCEP46-D05 in Plant Development

C-TERMINALLY ENCODED PEPTIDEs (CEPs) are a class of peptide hormones that have been shown in previous studies to play an important role in regulating the development and response to abiotic stress in model plants. However, their role in cotton is not well understood. In this study, we identified 54, 59, 34, and 35 CEP genes from Gossypium hirsutum (2n = 4x = 52, AD1), G. barbadense (AD2), G. arboreum (2n = 2X = 26, A2), and G. raimondii (2n = 2X = 26, D5), respectively. Sequence alignment and phylogenetic analyses indicate that cotton CEP proteins can be categorized into two subgroups based on the differentiation of their CEP domain. Chromosomal distribution and collinearity analyses show that most of the cotton CEP genes are situated in gene clusters, suggesting that segmental duplication may be a critical factor in CEP gene expansion. Expression pattern analyses showed that cotton CEP genes are widely expressed throughout the plant, with some genes exhibiting specific expression patterns. Ectopic expression of GhCEP46-D05 in Arabidopsis led to a significant reduction in both root length and seed size, resulting in a dwarf phenotype. Similarly, overexpression of GhCEP46-D05 in cotton resulted in reduced internode length and plant height. These findings provide a foundation for further investigation into the function of cotton CEP genes and their potential role in cotton breeding.

Fingerprint Finder: Identifying Genomic Fingerprint Sites in Cotton Cohorts for Genetic Analysis and Breeding Advancement

Genomic data in Gossypium provide numerous data resources for the cotton genomics community. However, to fill the gap between genomic analysis and breeding field work, detecting the featured genomic items of a subset cohort is essential for geneticists. We developed FPFinder v1.0 software to identify a subset of the cohort's fingerprint genomic sites. The FPFinder was developed based on the term frequency-inverse document frequency algorithm. With the short-read sequencing of an elite cotton pedigree, we identified 453 pedigree fingerprint genomic sites and found that these pedigree-featured sites had a role in cotton development. In addition, we applied FPFinder to evaluate the geographical bias of fiber-length-related genomic sites from a modern cotton cohort consisting of 410 accessions. Enriching elite sites in cultivars from the Yangtze River region resulted in the longer fiber length of Yangze River-sourced accessions. Apart from characterizing functional sites, we also identified 12,536 region-specific genomic sites. Combining the transcriptome data of multiple tissues and samples under various abiotic stresses, we found that several region-specific sites contributed to environmental adaptation. In this research, FPFinder revealed the role of the cotton pedigree fingerprint and region-specific sites in cotton development and environmental adaptation, respectively. The FPFinder can be applied broadly in other crops and contribute to genetic breeding in the future.

Exploring the role of GhN/AINV23: implications for plant growth, development, and drought tolerance

BACKGROUND

Neutral/alkaline invertases (N/AINVs) play a crucial role in plant growth, development, and stress response, by irreversibly hydrolyzing sucrose into glucose and fructose. However, research on cotton in this area is limited. This study aims to investigate GhN/AINV23, a neutral/alkaline invertase in cotton, including its characteristics and biological functions.

RESULTS

In our study, we analyzed the sequence information, three-dimensional (3D) model, phylogenetic tree, and cis-elements of GhN/AINV23. The localization of GhN/AINV23 was determined to be in the cytoplasm and cell membrane. Quantitative real-time polymerase chain reaction (qRT-PCR) results showed that GhN/AINV23 expression was induced by abscisic acid (ABA), exogenous sucrose and low exogenous glucose, and inhibited by high exogenous glucose. In Arabidopsis, overexpression of GhN/AINV23 promoted vegetative phase change, root development, and drought tolerance. Additionally, the virus-induced gene silencing (VIGS) assay indicated that the inhibition of GhN/AINV23 expression made cotton more susceptible to drought stress, suggesting that GhN/AINV23 positively regulates plant drought tolerance.

CONCLUSION

Our research indicates that GhN/AINV23 plays a significant role in plant vegetative phase change, root development, and drought response. These findings provide a valuable foundation for utilizing GhN/AINV23 to improve cotton yield.

Genome-Wide and Expression Pattern Analysis of the HIT4 Gene Family Uncovers the Involvement of GHHIT4_4 in Response to Verticillium Wilt in Gossypium hirsutum

Chromatin remodelers are essential for regulating plant growth, development, and responses to environmental stresses. HIT4 (HEAT-INTOLERANT 4) is a novel stress-induced chromatin remodeling factor that has been less studied in abiotic stress and stress resistance, particularly in cotton. In this study, we conducted a comprehensive analysis of the members of the HIT4 gene family in Gossypium hirsutum using bioinformatics methods, including phylogenetic relationships, gene organization, transcription profiles, phylogenetic connections, selection pressure, and stress response. A total of 18 HIT4 genes were identified in four cotton species, with six HIT4 gene members in upland cotton. Based on the evolutionary relationships shown in the phylogenetic tree, the 18 HIT4 protein sequences were classified into four distinct subgroups. Furthermore, we conducted chromosome mapping to determine the genomic locations of these genes and visually represented the structural characteristics of HIT4 in G. hirsutum. In addition, we predicted the regulatory elements in HIT4 in G. hirsutum and conducted an analysis of repetitive sequences and gene collinearity among HIT4 in four cotton species. Moreover, we calculated the Ka/Ks ratio for homologous genes to assess the selection pressure acting on HIT4. Using RNA-seq, we explored the expression patterns of HIT4 genes in G. hirsutum and Gossypium barbadense. Through weighted gene co-expression network analysis (WGCNA), we found that GHHIT4_4 belonged to the MEblue module, which was mainly enriched in pathways such as DNA replication, phagosome, pentose and glucuronate interconversions, steroid biosynthesis, and starch and sucrose metabolism. This module may regulate the mechanism of upland cotton resistance to Verticillium wilt through DNA replication, phagosome, and various metabolic pathways. In addition, we performed heterologous overexpression of GH_D11G0591 (GHHIT4_4) in tobacco, and the results showed a significant reduction in disease index compared to the wild type, with higher expression levels of disease resistance genes in the transgenic tobacco. After conducting a VIGS (virus-induced gene silencing) experiment in cotton, the results indicated that silencing GHHIT4_4 had a significant impact, the resistance to Verticillium wilt weakened, and the internode length of the plants significantly decreased by 30.7% while the number of true leaves increased by 41.5%. qRT-PCR analysis indicated that GHHIT4_4 mainly enhanced cotton resistance to Verticillium wilt by indirectly regulating the PAL, 4CL, and CHI genes. The subcellular localization results revealed that GHHIT4_4 was predominantly distributed in the mitochondria and nucleus. This study offers preliminary evidence for the involvement of the GHHIT4_4 in cotton resistance to Verticillium wilt and lays the foundation for further research on the disease resistance mechanism of this gene in cotton.

GhWRKY4 binds to the histone deacetylase GhHDA8 promoter to regulate drought and salt tolerance in Gossypium hirsutum

Soil drought and salinization, caused by water deficiency, have become the greatest concerns limiting crop production. Up to now, the WRKY transcription factor and histone deacetylase have been shown to be involved in drought and salt responses. However, the molecular mechanism underlying their interaction remains unclear in cotton. Herein, we identified GhWRKY4, a member of WRKY gene family, which is induced by drought and salt stress and is located in the nucleus. The ectopic expression of GhWRKY4 in Arabidopsis enhanced drought and salt tolerance, and suppressing GhWRKY4 in cotton increased susceptibility to drought and salinity. Subsequently, DAP-seq analysis revealed that the W box element in the promoter of stress-induced genes could potentially be the binding target for GhWRKY4 protein. GhWRKY4 binds to the promoters of GhHDA8 and GhNHX7 via W box element, and the expression level of GhHDA8 was increased in GhWRKY4-silenced plants. In addition, GhHDA8-overexpressed Arabidopsis were found to be hypersensitive to drought and salt stress, while silencing of GhHDA8 enhanced drought and salt tolerance in cotton. The stress-related genes, such as GhDREB2A, GhRD22, GhP5CS, and GhNHX7, were induced in GhHDA8-silenced plants. Our findings indicate that the GhWRKY4-GhHDA8 module regulates drought and salt tolerance in cotton. Collectively, the results provide new insights into the coordination of transcription factors and histone deacetylases in regulating drought and salt stress responses in plants.

Genome-Wide Identification and Expression Analysis Unveil the Involvement of the Cold Shock Protein (CSP) Gene Family in Cotton Hypothermia Stress

Cold shock proteins (CSPs) are DNA/RNA binding proteins with crucial regulatory roles in plant growth, development, and stress responses. In this study, we employed bioinformatics tools to identify and analyze the physicochemical properties, conserved domains, gene structure, phylogenetic relationships, cis-acting elements, subcellular localization, and expression patterns of the cotton CSP gene family. A total of 62 CSP proteins were identified across four cotton varieties (Gossypium arboreum, Gossypium raimondii, Gossypium barbadense, Gossypium hirsutum) and five plant varieties (Arabidopsis thaliana, Brassica chinensis, Camellia sinensis, Triticum aestivum, and Oryza sativa). Phylogenetic analysis categorized cotton CSP proteins into three evolutionary branches, revealing similar gene structures and motif distributions within each branch. Analysis of gene structural domains highlighted the conserved CSD and CCHC domains across all cotton CSP families. Subcellular localization predictions indicated predominant nuclear localization for CSPs. Examination of cis-elements in gene promoters revealed a variety of elements responsive to growth, development, light response, hormones, and abiotic stresses, suggesting the potential regulation of the cotton CSP family by different hormones and their involvement in diverse stress responses. RT-qPCR results suggested that GhCSP.A1, GhCSP.A2, GhCSP.A3, and GhCSP.A7 may play roles in cotton's response to low-temperature stress. In conclusion, our findings underscore the significant role of the CSP gene family in cotton's response to low-temperature stress, providing a foundational basis for further investigations into the functional aspects and molecular mechanisms of cotton's response to low temperatures.

Rapidly mining candidate cotton drought resistance genes based on key indicators of drought resistance

BACKGROUND

Focusing on key indicators of drought resistance is highly important for quickly mining candidate genes related to drought resistance in cotton.

RESULTS

In the present study, drought resistance was identified in drought resistance-related RIL populations during the flowering and boll stages, and multiple traits were evaluated; these traits included three key indicators: plant height (PH), single boll weight (SBW) and transpiration rate (Tr). Based on these three key indicators, three groups of extreme mixing pools were constructed for BSA-seq. Based on the mapping interval of each trait, a total of 6.27 Mb QTL intervals were selected on chromosomes A13 (3.2 Mb), A10 (2.45 Mb) and A07 (0.62 Mb) as the focus of this study. Based on the annotation information and qRT‒PCR analysis, three key genes that may be involved in the drought stress response of cotton were screened: GhF6'H1, Gh3AT1 and GhPER55. qRT‒PCR analysis of parental and extreme germplasm materials revealed that the expression of these genes changed significantly under drought stress. Cotton VIGS experiments verified the important impact of key genes on cotton drought resistance.

CONCLUSIONS

This study focused on the key indicators of drought resistance, laying the foundation for the rapid mining of drought-resistant candidate genes in cotton and providing genetic resources for directed molecular breeding of drought resistance in cotton.

GhBRX.1, GhBRX.2, and GhBRX4.3 improve resistance to salt and cold stress in upland cotton

Introduction

Abiotic stress during growth readily reduces cotton crop yield. The different survival tactics of plants include the activation of numerous stress response genes, such as BREVIS RADIX (BRX).

Methods

In this study, the BRX gene family of upland cotton was identified and analyzed by bioinformatics method, three salt-tolerant and cold-resistant GhBRX genes were screened. The expression of GhBRX.1, GhBRX.2 and GhBRXL4.3 in upland cotton was silenced by virus-induced gene silencing (VIGS) technique. The physiological and biochemical indexes of plants and the expression of related stress-response genes were detected before and after gene silencing. The effects of GhBRX.1, GhBRX.2 and GhBRXL4.3 on salt and cold resistance of upland cotton were further verified.

Results and discussion

We discovered 12, 6, and 6 BRX genes in Gossypium hirsutum, Gossypium raimondii and Gossypium arboreum, respectively. Chromosomal localization indicated that the retention and loss of GhBRX genes on homologous chromosomes did not have a clear preference for the subgenomes. Collinearity analysis suggested that segmental duplications were the main force for BRX gene amplification. The upland cotton genes GhBRX.1, GhBRX.2 and GhBRXL4.3 are highly expressed in roots, and GhBRXL4.3 is also strongly expressed in the pistil. Transcriptome data and qRT‒PCR validation showed that abiotic stress strongly induced GhBRX.1, GhBRX.2 and GhBRXL4.3. Under salt stress and low-temperature stress conditions, the activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) and the content of soluble sugar and chlorophyll decreased in GhBRX.1-, GhBRX.2- and GhBRXL4.3-silenced cotton plants compared with those in the control (TRV: 00). Moreover, GhBRX.1-, GhBRX.2- and GhBRXL4.3-silenced cotton plants exhibited greater malondialdehyde (MDA) levels than did the control plants. Moreover, the expression of stress marker genes (GhSOS1, GhSOS2, GhNHX1, GhCIPK6, GhBIN2, GhSnRK2.6, GhHDT4D, GhCBF1 and GhPP2C) decreased significantly in the three target genes of silenced plants following exposure to stress. These results imply that the GhBRX.1, GhBRX.2 and GhBRXL4.3 genes may be regulators of salt stress and low-temperature stress responses in upland cotton.

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

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

GhVOZ1-AVP1 module positively regulates salt tolerance in upland cotton (Gossypium hirsutum L.)

Vascular Plant One‑zinc Finger (VOZ) transcription factor can respond to a variety of abiotic stresses, however its function in cotton and the molecular mechanisms of response to salt tolerance remained unclear. In this study, we found that GhVOZ1 is highly expressed in stamen and stem of cotton under normal conditions. The expression of GhVOZ1 increased significantly after 3 h of salt treatment in three-leaf staged upland cotton. Overexpressed transgenic lines of GhVOZ1 in Arabidopsis and upland cotton were treated with salt stress and we found that GhVOZ1 could respond positively to salt stress. GhVOZ1 can regulate Arabidopsis Vacuolar Proton Pump Pyrophosphatase (H+-PPase) gene (AVP1) expression through specific binding to GCGTCTAAAGTACGC site on GhAVP1 promoter, which was examined through Dual-luciferase assay and Electrophoretic mobility shift assay (EMSA). AVP1 expression was significantly increased in Arabidopsis with GhVOZ1 overexpression, while GhAVP1 expression was decreased in virus induced gene silenced (VIGS) cotton plants of GhVOZ1. Knockdown of GhAVP1 expression in cotton plants by VIGS showed decreased superoxide dismutase (SOD) and peroxidase (POD) activities, whereas an increased malondialdehyde (MDA) content and ultimately decreased salt tolerance. The GhVOZ1-AVP1 module could maintain sodium ion homeostasis through cell ion transport and positively regulate the salt tolerance in cotton, providing new ideas and insights for the study of salt tolerance.

The Silencing of GhPIP5K2 and GhPIP5K22 Weakens Abiotic Stress Tolerance in Upland Cotton (Gossypium hirsutum)

Phosphatidylinositol 4-phosphate 5-kinases (PIP5Ks), essential enzymes in the phosphatidylinositol signaling pathway, are crucial for the abiotic stress responses and the overall growth and development of plants. However, the GhPIP5Ks had not been systematically studied, and their function in upland cotton was unknown. This study identified a total of 28 GhPIP5Ks, and determined their chromosomal locations, gene structures, protein motifs and cis-acting elements via bioinformatics analysis. A quantitative real-time PCR (qRT‒PCR) analysis showed that most GhPIP5Ks were upregulated under different stresses. A virus-induced gene silencing (VIGS) assay indicated that the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activities were significantly decreased, while malondialdehyde (MDA) content were significantly increased in GhPIP5K2- and GhPIP5K22-silenced upland cotton plants under abiotic stress. Furthermore, the expression of the stress marker genes GhHSFB2A, GhHSFB2B, GhDREB2A, GhDREB2C, GhRD20-1, GhRD29A, GhBIN2, GhCBL3, GhNHX1, GhPP2C, GhCBF1, GhSnRK2.6 and GhCIPK6 was significantly decreased in the silenced plants after exposure to stress. These results revealed that the silencing of GhPIP5K2 and GhPIP5K22 weakened the tolerance to abiotic stresses. These discoveries provide a foundation for further inquiry into the actions of the GhPIP5K gene family in regulating the response and resistance mechanisms of cotton to abiotic stresses.

Genome-Wide and Expression Pattern Analysis of the DVL Gene Family Reveals GhM_A05G1032 Is Involved in Fuzz Development in G. hirsutum

DVL is one of the small polypeptides which plays an important role in regulating plant growth and development, tissue differentiation, and organ formation in the process of coping with stress conditions. So far, there has been no comprehensive analysis of the expression profile and function of the cotton DVL gene. According to previous studies, a candidate gene related to the development of fuzz was screened, belonging to the DVL family, and was related to the development of trichomes in Arabidopsis thaliana. However, the comprehensive identification and systematic analysis of DVL in cotton have not been conducted. In this study, we employed bioinformatics approaches to conduct a novel analysis of the structural characteristics, phylogenetic tree, gene structure, expression pattern, evolutionary relationship, and selective pressure of the DVL gene family members in four cotton species. A total of 117 DVL genes were identified, including 39 members in G. hirsutum. Based on the phylogenetic analysis, the DVL protein sequences were categorized into five distinct subfamilies. Additionally, we successfully mapped these genes onto chromosomes and visually represented their gene structure information. Furthermore, we predicted the presence of cis-acting elements in DVL genes in G. hirsutum and characterized the repeat types of DVL genes in the four cotton species. Moreover, we computed the Ka/Ks ratio of homologous genes across the four cotton species and elucidated the selective pressure acting on these homologous genes. In addition, we described the expression patterns of the DVL gene family using RNA-seq data, verified the correlation between GhMDVL3 and fuzz development through VIGS technology, and found that some DVL genes may be involved in resistance to biotic and abiotic stress conditions through qRT-PCR technology. Furthermore, a potential interaction network was constructed by WGCNA, and our findings demonstrated the potential of GhM_A05G1032 to interact with numerous genes, thereby playing a crucial role in regulating fuzz development. This research significantly contributed to the comprehension of DVL genes in upland cotton, thereby establishing a solid basis for future investigations into the functional aspects of DVL genes in cotton.

PRMD: an integrated database for plant RNA modifications

The scope and function of RNA modifications in model plant systems have been extensively studied, resulting in the identification of an increasing number of novel RNA modifications in recent years. Researchers have gradually revealed that RNA modifications, especially N6-methyladenosine (m6A), which is one of the most abundant and commonly studied RNA modifications in plants, have important roles in physiological and pathological processes. These modifications alter the structure of RNA, which affects its molecular complementarity and binding to specific proteins, thereby resulting in various of physiological effects. The increasing interest in plant RNA modifications has necessitated research into RNA modifications and associated datasets. However, there is a lack of a convenient and integrated database with comprehensive annotations and intuitive visualization of plant RNA modifications. Here, we developed the Plant RNA Modification Database (PRMD; http://bioinformatics.sc.cn/PRMD and http://rnainformatics.org.cn/PRMD) to facilitate RNA modification research. This database contains information regarding 20 plant species and provides an intuitive interface for displaying information. Moreover, PRMD offers multiple tools, including RMlevelDiff, RMplantVar, RNAmodNet and Blast (for functional analyses), and mRNAbrowse, RNAlollipop, JBrowse and Integrative Genomics Viewer (for displaying data). Furthermore, PRMD is freely available, making it useful for the rapid development and promotion of research on plant RNA modifications.