This study reveals genetic factors influencing macronutrient content in cottonseeds, identifying key loci and candidate genes for breeding strategies to improve seed nutrition. Macronutrients such as potassium (K), calcium (Ca), and magnesium (Mg) are essential for crop growth, seed quality, and nutrition and health of humans and animals. Insufficient levels of these macronutrients in cottonseeds can lead to malnutrition in animals consuming cottonseed meal-based products. However, the variation and genetic basis of macronutrient content in cottonseeds remain unclear. Here, we investigated the content of K, Ca, and Mg in cottonseeds from 276 cotton accessions grown across diverse ecological regions in China. All three macronutrients exhibited continuous and considerable large variation in the population, with broad-sense heritability values of 70.14

Sucrose transporters (SUTs) are essential for assimilate translocation from source to sink tissues, playing a vital role in plant growth and development. While the characteristics and biological functions of SUT genes have been extensively studied in various higher plants, their roles in Nicotiana tabacum remain poorly understood. In this study, eight NtSUT genes were identified in tobacco, which were classified into three distinct evolutionary clades. Members within the same clade exhibited similar exon-intron structures and motif patterns. Promoter analysis revealed cis-acting elements involved in regulating growth, phytohormone signaling, and abiotic stress responses. Subcellular localization showed that NtSUT proteins are predominantly localized to the plasma membrane. Yeast complementation assays confirmed their functional role in sucrose transport. Expression profiling under NaCl and PEG treatments indicated that NtSUT genes, especially NtSUT2, are crucial for stress responses. Further esculin absorption experiments conducted on yeast mutants and tobacco roots confirmed the role of NtSUT2-mediated sucrose transport in response to abiotic stress. Our research is the first to establish a method using esculin to study sucrose transport in tobacco, confirming the role of sucrose transport in the response of tobacco to abiotic stress.

Potassium (K+), an essential macronutrient for plant growth and stress adaptation, becomes physiologically stressful when overaccumulated in soil. While K fertilization enhances cotton (Gossypium hirsutum) fiber quality and yield, the consequential KCl-induced ionic stress has emerged as a critical agricultural challenge demanding molecular-level resolution. This study unveils the previously unexplored epigenetic mechanisms mediated by histone H3 lysine 27 trimethylation (H3K27me3) in cotton's adaptation to KCl stress. Through integrated cleavage under targets and tagmentation (CUT&Tag) chromatin profiling and transcriptome sequencing, we demonstrate that KCl stress triggers genome-wide attenuation of H3K27me3 deposition, concomitant with characteristic stress phenotypes in cotton seedlings. Suppression of H3K27me3 using RDS 3434 significantly ameliorated KCl-induced physiological damage, thereby supporting a functional correlation between this epigenetic mark and stress tolerance. Mechanistic analyses revealed 48 genes exhibiting inverse correlation between H3K27me3 enrichment and transcriptional activation, including 2 that encode pivotal salt-tolerance regulators: Glutathione Synthase1 (GhGSH1) and Salt-Related MYB1 (GhSRM1). Virus-induced gene silencing validation confirmed these H3K27me3-associated genes as essential components of cotton's ionic stress response network. Our findings delineate the epigenetic landscape associated with KCl stress adaptation and highlight H3K27me3-mediated chromatin remodeling as a critical regulatory layer in plant abiotic stress responses. This work provides insights into epigenetic engineering strategies for developing stress-resilient cotton cultivars.

Cotton fiber elongation is a complex developmental process regulated by hormonal and metabolic signals. Auxin (indole-3-acetic acid, IAA) and brassinosteroid (BR) play crucial roles in cotton fiber development, but the mechanism by which they coordinate to regulate fiber elongation remains unclear. In this study, we determined that IAA levels gradually increase during fiber development and are higher in long-fiber varieties. In vitro ovule culture experiments revealed that IAA promotes fiber elongation in a dose-dependent manner. Transcriptome analysis showed that IAA activates BR biosynthesis and the BR signaling pathway, implying crosstalk between the two hormones. Interestingly, IAA could partially rescue fiber elongation caused by BR deficiency due to brassinazole treatment and in pag1 mutants, and BR supplementation partially alleviated fiber inhibition resulting from impaired IAA transport or IAA deficiency. However, neither hormone fully compensated for the absence of the other, indicating that both serve non-redundant roles in fiber elongation. Additionally, inhibiting glucose signaling by suppressing hexokinase activity through N-acetylglucosamine impaired fiber growth, but this could be rescued by exogenous application of either IAA or BR, suggesting that glucose acts upstream of IAA and BR, which cooperatively regulate the elongation of cotton fibers.

SWEET (sugars will eventually be exported transporter) proteins are vital for sugar transport in plants, mediating the movement of glucose, fructose, and sucrose, and playing key roles in growth, development, and stress responses. This study identified 1246 SWEET proteins across 59 plant species, spanning from chlorophytes to eudicots. Phylogenetic analysis revealed that SWEET proteins originated in chlorophytes and diverged into four clades (I-IV). Chlorophyte SWEETs, classified in clade II, lacked transport activity and were localized on the vacuolar membrane. In charophytes, clade I SWEETs acquired the ability to transport glucose and fructose, marking a significant adaptation during the transition to terrestrial plants. In bryophytes, clade II SWEETs transport glucose and fructose, localized on the vacuolar membrane. In vascular plants, clade IV SWEETs, which emerged in lycophytes, exhibited fructose transport activity and localized to the plasma or vacuolar membranes. Clade III SWEETs, exclusive to seed plants, are specialized in sucrose transport, which is crucial for long-distance sugar distribution. Sequence and structural analysis revealed that the highly conserved transmembrane regions form the triple-helix bundle essential for sugar transport. In contrast, the N-terminal and C-terminal regions contribute to substrate specificity and structural folding. Functional assays confirmed that removal of these non-conserved regions abolishes transport activity. In conclusion, this study provides a comprehensive analysis of the evolutionary origins, functional diversification, and structural significance of SWEET proteins, underscoring their pivotal roles in carbohydrate metabolism and plant diversification. These findings offer valuable insights into the molecular mechanisms underlying sugar transport and its evolutionary adaptations in plants.

Histone methylation is pivotal in regulating the expression of numerous essential functional genes in plants. However, its specific function and mechanism in cotton fiber cell initiation remain poorly understood. The upland cotton (Gossypium hirsutum L.) variety Xuzhou142 (Xu142) and its fuzzless-lintless mutant Xu142 fl are ideal model materials for studying cotton fiber cell development. In vitro ovule culture analysis showed that the histone H3 lysine 27 trimethylation (H3K27me3) inhibitor RDS 3434 could inhibit fiber cell initiation and development. Cleavage under targets and tagmentation (CUT&Tag) and RNA sequencing (RNA-seq) data of-1, 0, and 1 day post-anthesis (DPA) ovules showed that H3K27me3 regulates fiber cell initiation by highly accumulating in Xu142 than in Xu142 fl. It was also found that H3K27me3 was negatively correlated with gene transcription, as 227 expressed genes showed an opposite trend to the H3K27me3 modification level and were identified to participate in multiple signaling pathways. Furthermore, the expression levels often potential genes related to fiber development were confirmed to correlate with H3K27me3 levels. The results demonstrate the critical role of H3K27me3 in fiber development process and present evidence supporting its involvement in cotton fiber cell initiation. The study lays the foundation and provides genetic resources for further investigations into genes related to fiber development.

We characterized the WAK gene family in Gossypium barbadense and revealed the potential function of GbWAK5 in regulating salt tolerance by modulating ion homeostasis. Soil salinization is one of the main factors restricting cotton production. Although the role of the wall-associated kinases (WAKs) in plants has been extensively studied, its response to salt stress in sea-island cotton (Gossypium barbadense L.) has not been reported. Here, we conducted a whole-genome analysis of the WAK gene family in G. barbadense, identifying a total of 70 GbWAK genes, which were classified into five clades. Segmental and tandem duplication events have contributed to the expansion of the GbWAK gene family. A large number of cis-acting elements were predicted in the GbWAK promoter region. Through RNA sequencing, 37 GbWAKs that potentially play a role in cotton's response to salt stress were screened out, among which 10 genes with sustained up-regulated expression were confirmed by quantitative real-time PCR (qRT-PCR). GbWAK5, a member of Clade II, was significantly up-regulated following NaCl treatment and exhibited a typical WAK structure. Subcellular localization indicated that GbWAK5 is localized on the plasma membrane. Virus-induced gene silencing (VIGS) experiments revealed that the knockdown of GbWAK5 resulted in more severe dehydration and wilting in plants compared to the control under NaCl treatment. RNA-seq analysis revealed that several ion transport-related genes were down-regulated in TRV:GbWAK5 plants under salt stress, while TRV:GbWAK5 plants accumulated more Na+ and exhibited a higher Na+/K+ ratio compared to TRV:00 plants. These results offer a comprehensive analysis of the G. barbadense WAK gene family for the first time, and conclude that GbWAK5 is a promising gene for improving cotton's resistance to salt stress.

SINA (Seven in absentia) E3 ligases are critical components of the ubiquitin-proteasome system (UPS). They are responsible for ubiquitination and are involved in numerous cellular processes. The functional mechanisms of SINAs have been extensively studied in a few angiosperms. However, our understanding of the origin and evolution of plant SINA genes remain limited. Here we performed a large-scale comprehensive analysis of SINA proteins from various plant lineages. The plant SINA family genes likely originated from a common ancestral gene prior to the divergence of bryophyte and gave rise to two clades. Within clade I, subsequent parallel innovations in lycophytes and ferns resulted in the formation of two branches. All SINA proteins contain an N-terminal cysteine-rich really interesting new gene (RING) domain for ubiquitination, two zinc-finger motifs, and a C-terminal domain required for substrate-binding and dimerization. The SINA genes gains and losses occurred in angiosperms, resulting in an increase in the number of gene copies in eudicots and monocots. The Gossypium genus SINAs showed a tendency for expansion via whole-genome duplication and polyploidy. Finally, global expression patterns revealed the functional diversification of SINA genes in developmental stage and response to hormones and abiotic stresses in Arabidopsis and rice. These findings provide an insight into the evolution and diversification of SINA E3 ligases in plants and enhance our understanding of the role they play in determining substrate specificity and environment stress adaptations in angiosperms.

Copper(II) (Cu2+) is essential for plant growth and development. However, high concentrations are extremely toxic to plants. We investigated the tolerance mechanism of cotton under Cu2+ stress in a hybrid cotton variety (Zhongmian 63) and two parent lines with different Cu2+ concentrations (0, 0.2, 50, and 100 μM). The stem height, root length, and leaf area of cotton seedlings had decreased growth rates in response to increasing Cu2+ concentrations. Increasing Cu2+ concentration promoted Cu2+ accumulation in all three cotton genotypes' roots, stems, and leaves. However, compared with the parent lines, the roots of Zhongmian 63 were richer in Cu2+ and had the least amount of Cu2+ transported to the shoots. Moreover, excess Cu2+ also induced changes in cellular redox homeostasis, causing accumulation of hydrogen peroxide (H2O2) and malondialdehyde (MDA). Conversely, antioxidant enzyme activity increased, while photosynthetic pigment content decreased. Our findings indicated that the hybrid cotton variety fared well under Cu2+ stress. This creates a theoretical foundation for the further analysis of the molecular mechanism of cotton resistance to copper and suggests the potential of the large-scale planting of Zhongmian 63 in copper-contaminated soils.

Protein ubiquitination is essential for plant growth and responses to the environment. The SEVEN IN ABSENTIA (SINA) ubiquitin ligases have been extensively studied in plants, but information on their roles in fiber development is limited. Here, we identified GhSINA1 in Upland cotton (Gossypium hirsutum), which has a conserved RING finger domain and SINA domain. Quantitative real-time PCR (qRT-PCR) analysis showed that GhSINA1 was preferentially expressed during fiber initiation and elongation, especially during initiation in the fuzzless-lintless cotton mutant. Subcellular localization experiments indicated that GhSINA1 localized to the nucleus. In vitro ubiquitination analysis revealed that GhSINA1 has E3 ubiquitin ligase activity. Ectopic overexpression of GhSINA1 in Arabidopsis thaliana reduced the number and length of root hairs and trichomes. Yeast two-hybrid (Y2H), firefly luciferase complementation imaging (LCI), and bimolecular fluorescence complementation (BiFC) assays demonstrated that the GhSINA1 proteins could interact with each other to form homodimers and heterodimers. Overall, these results suggest that GhSINA1 may act as a negative regulator in cotton fiber development through homodimerization and heterodimerization.

Verticillium wilt (VW), Fusarium wilt (FW) and Root-knot nematode (RKN) are the main diseases affecting cotton production. However, many reported quantitative trait loci (QTLs) for cotton resistance have not been used for agricultural practices because of inconsistencies in the cotton genetic background. The integration of existing cotton genetic resources can facilitate the dis-covery of important genomic regions and candidate genes involved in disease resistance. Here, an improved and comprehensive meta-QTL analysis was conducted on 487 disease resistant QTLs from 31 studies in the last two decades. A consensus linkage map with genetic overall length of 3006.59 cM containing 8650 markers was constructed. A total of 28 Meta-QTLs (MQTLs) were discovered, among which nine MQTLs were identified as related to resistance to multiple diseases. Candidate genes were predicted based on public transcriptome data and enriched in pathways related to disease resistance. This study used a method based on the integration of Meta-QTL, known genes and transcriptomics to reveal major genomic regions and putative candidate genes for resistance to multiple diseases, providing a new basis for marker-assisted selection of high disease resistance in cotton breeding.

Salinity is a major abiotic stress that restricts cotton growth and affects fiber yield and quality. Although studies on salt tolerance have achieved great progress in cotton since the completion of cotton genome sequencing, knowledge about how cotton copes with salt stress is still scant. S-adenosylmethionine (SAM) plays important roles in many organelles with the help of the SAM transporter, and it is also a synthetic precursor for substances such as ethylene (ET), polyamines (PAs), betaine, and lignin, which often accumulate in plants in response to stresses. This review focused on the biosynthesis and signal transduction pathways of ET and PAs. The current progress of ET and PAs in regulating plant growth and development under salt stress has been summarized. Moreover, we verified the function of a cotton SAM transporter and suggested that it can regulate salt stress response in cotton. At last, an improved regulatory pathway of ET and PAs under salt stress in cotton is proposed for the breeding of salt-tolerant varieties.

Key message The study of the origin, evolution, and diversification of the wall-associated kinase gene family in plants facilitates their functional investigations in the future. Abstract Wall-associated kinases (WAKs) make up one subfamily of receptor-like kinases (RLKs), and function directly in plant cell elongation and responses to biotic and abiotic stresses. The biological functions of WAKs have been extensively characterized in angiosperms; however, the origin and evolutionary history of the WAK family in green plants remain unclear. Here, we performed a comprehensive analysis of the WAK family to reveal its origin, evolution, and diversification in green plants. In total, 1061 WAK genes were identified in 37 species from unicellular algae to multicellular plants, and the results showed that WAK genes probably originated before bryophyte differentiation and were widely distributed in land plants, especially angiosperms. The phylogeny indicated that the land plant WAKs gave rise to five clades and underwent lineage-specific expansion after species differentiation. Cis -acting elements and expression patterns analyses of WAK genes in Arabidopsis and rice demonstrated the functional diversity of WAK genes in these two species. Many gene gains and losses have occurred in angiosperms, leading to an increase in the number of gene copies. The evolutionary trajectory of the WAK family during polyploidization was uncovered using Gossypium species. Our results provide insights into the evolution of WAK genes in green plants, facilitating their functional investigations in the future.

Histone demethylases containing JumonjiC (JmjC) domains regulate gene transcription and chromatin structure by changing the methylation status of lysine residues and play an important role in plant growth and development. In this study, a total of 332 JmjC family genes were identified from 21 different plant species. The evolutionary analysis results showed that the JmjC gene was detected in each species, that is, the gene has already appeared in algae. The phylogenetic analysis showed that the KDM3/JHDM2 subfamily genes may have appeared when plants transitioned from water to land, but were lost in lycophytes (Selaginella moellendorffii). During the evolutionary process, some subfamily genes may have been lost in individual species. According to the analysis of the conserved domains, all of the plant JmjC genes contained a typical JmjC domain, which was highly conserved during plant evolution. The analysis of cis-acting elements showed that the promoter region of the JmjC gene was rich in phytohormones and biotic and abiotic stress-related elements. The transcriptome data analysis and protein interaction analyses showed that JmjC genes play an important role in plant growth and development. The results clarified the evolutionary history of JmjC family genes in plants and lay the foundation for the analysis of the biological functions of JmjC family genes.

In plants, glucose (Glc) plays important roles, as a nutrient and signal molecule, in the regulation of growth and development. However, the function of Glc in fiber development of upland cotton (Gossypium hirsutum) is unclear. Here, using gas chromatography-mass spectrometry (GC-MS), we found that the Glc content in fibers was higher than that in ovules during the fiber elongation stage. In vitro ovule culture revealed that lower Glc concentrations promoted cotton fiber elongation, while higher concentrations had inhibitory effects. The hexokinase inhibitor N-acetylglucosamine (NAG) inhibited cotton fiber elongation in the cultured ovules, indicating that Glc-mediated fiber elongation depends on the Glc signal transduced by hexokinase. RNA sequencing (RNA-seq) analysis and hormone content detection showed that 150mM Glc significantly activated brassinosteroid (BR) biosynthesis, and the expression of signaling-related genes was also increased, which promoted fiber elongation. In vitro ovule culture clarified that BR induced cotton fiber elongation in a dose-dependent manner. In hormone recovery experiments, only BR compensated for the inhibitory effects of NAG on fiber elongation in a Glc-containing medium. However, the ovules cultured with the BR biosynthetic inhibitor brassinazole and from the BR-deficient cotton mutant pag1 had greatly reduced fiber elongation at all the Glc concentrations tested. This demonstrates that Glc does not compensate for the inhibition of fiber elongation caused by BR biosynthetic defects, suggesting that the BR signaling pathway works downstream of Glc during cotton fiber elongation. Altogether, our study showed that Glc plays an important role in cotton fibre elongation, and crosstalk occurs between Glc and BR signaling during modulation of fiber elongation.

在我国长江中下游地区的棉花种植区域,由于受到长时间梅雨季和强降雨的影响,棉花在生长发育时期容易受到涝害胁迫,棉花的生理生化特征和分子机制都发生了变化,植株地下部分缺氧使地上部分的干物质合成受阻,导致棉花产量和品质严重下降,这成为当前长江流域棉花产业稳定的一大问题.综述了涝害对棉花生理生化特征以及品质产量的影响,并进一步分析了棉花耐涝的分子机制,为棉花耐涝种质资源筛选和新品种选育提供了理论依据.

每年的6―8月是长江流域棉区棉花生长的关键时节,通常伴随着高温胁迫.环境温度过高,棉花种子存活率、发芽率,苗期植株的生长速率、株高、茎粗、叶片数量,花铃期的开花率、结铃率,以及皮棉产量、籽棉产量等都会受到严重影响,最终导致棉花减产甚至植株死亡.通过分析国内外相关研究进展,解析高温对棉花的种子萌发、植株营养生长、生殖生长及产量、品质、主要代谢过程的影响,同时探究棉花生理生化和分子的适应机理,为筛选耐高温棉花种质资源和选育耐高温棉花新品种提供有效方法和理论依据.

The wall-associated kinases (WAKs) and WAK-like kinases (WAKLs) form a group of receptor-like kinases (RLKs) with extracellular domains tightly linked to the cell wall. The WAKs/WAKLs have been known to be involved in plant growth, development, and stress responses. However, the functions of WAKs/WAKLs are less well known in cotton. In this study, 58, 66, and 99 WAK/WAKL genes were identified in Gossypium arboreum, G. raimondii, and G. hirsutum, respectively. Phylogenetic analysis showed they were classified into five groups, with two groups specific to cotton. Collinearity analysis revealed that segmental and tandem duplications resulted in expansion of the WAK/WAKL gene family in cotton. Moreover, the Ka/Ks ratios indicated this family was exposed to purifying selection pressure during evolution. The structures of the GhWAK/WAKL genes and encoded proteins suggested the functions of WAKs/WAKLs in cotton were conserved. Transient expression of four WAK/WAKL-GFP fusion constructs in Arabidopsis protoplasts indicated that they were localized on the plasma membrane. The cis-elements in the GhWAK/WAKL promoters were responsive to multiple phytohormones and abiotic stresses. Expression profiling showed that GhWAK/WAKL genes were induced by various abiotic stresses. This study provides insights into the evolution of WAK/WAKL genes and presents fundamental information for further analysis in cotton.

Cotton is one of the most important fiber and oil crops in the world. Chloroplast genomes harbor their own genetic materials and are considered to be highly conserved. Transfer RNAs (tRNAs) act as “bridges” in protein synthesis by carrying amino acids. Currently, the variation and evolutionary characteristics of tRNAs in the cotton chloroplast genome are poorly understood. Here, we analyzed the structural variation and evolution of chloroplast tRNA (cp tRNA) based on eight diploid and two allotetraploid cotton species. We also investigated the nucleotide evolution of chloroplast genomes in cotton species. We found that cp tRNAs in cotton encoded 36 or 37 tRNAs, and 28 or 29 anti-codon types with lengths ranging from 60 to 93 nucleotides. Cotton chloroplast tRNA sequences possessed specific conservation and, in particular, the Ψ-loop contained the conserved U-U-C-X3-U. The cp tRNAs of Gossypium L. contained introns, and cp tRNAIle contained the anti-codon (C-A-U), which was generally the anti-codon of tRNAMet. The transition and transversion analyses showed that cp tRNAs in cotton species were iso-acceptor specific and had undergone unequal rates of evolution. The intergenic region was more variable than coding regions, and non-synonymous mutations have been fixed in cotton cp genomes. On the other hand, phylogeny analyses indicated that cp tRNAs of cotton were derived from several inferred ancestors with greater gene duplications. This study provides new insights into the structural variation and evolution of chloroplast tRNAs in cotton plants. Our findings could contribute to understanding the detailed characteristics and evolutionary variation of the tRNA family.

以6个陆地棉品种(系)为亲本,采用NCⅡ交配设计配制9个杂交组合,对杂交组合F1、F2的表型性状、产量性状以及纤维品质性状进行比较分析.结果表明:大部分组合F1和F2在单株果枝数和单株结铃数存在一定竞争优势,F2铃重和衣分存在竞争衰退现象,导致F2皮棉产量较F1明显降低.但有些强优势组合的杂种优势在F2中仍能很好延续,其中组合5的F2籽棉和皮棉产量较F1提高,说明组合5的F2在产量方面具有一定杂种优势,可以利用其F2的杂种优势.