Fiber elongation rate is an essential characteristic of cotton fiber in the textile industry, yet it has been largely overlooked in genetic studies. Gibberellins (GAs) and auxin (IAA) are recognized for their role in directing numerous developmental processes in plants by influencing cell differentiation and elongation. However, the degree to which GA-IAA interaction governs cellular elongation in cotton fiber cells remains to be fully understood. In this study, we identified a causal gene, Gibberellic Acid-Stimulated in Arabidopsis 24 (GhGASA24), that appears to be responsible for fiber elongation rate via regulating fiber cell wall thickness. Subsequent experiments revealed that GhGASA24 influences cell wall formation by promoting the expression of GhCesA8 and GhCesA10. Our findings suggest that Auxin Response Factor 2 (GhARF2) regulates fiber elongation rate by directly binding to the AuxRE elements in GhGASA24 promoter. In addition, we identified Growth Regulation Factor 4 (GhGRF4) as a transcription factor that interacts with GhARF2 to form a heterodimer complex, which also transcriptionally activates GhGASA24. Intriguingly, GhGRF4 regulates GhARF2 expression by directly binding to its promoter, thereby acting as a cascade regulator to enhance the transcriptional levels of GhGASA24. We propose that the GhGRF4/GhARF2-GhGASA24-GhCesAs module may contribute to fiber cell wall thickness by modulating cellulose biosynthesis, and provide a theoretical basis for improvement of fiber quality.

Background Cotton fiber is a model tissue for studying microtubule-associated proteins (MAPs). The Xklp2 (TPX2) proteins that belong to the novel MAPs member mainly participate in the formation and development of microtubule (MT). However, there is a lack of studies concerning the systematic characterization of the TPX2 genes family in cotton. Therefore, the identification and portrayal of G. hirsutum TPX2 genes can provide key targets for molecular manipulation in the breeding of cotton fiber improvement. Result In this study, TPX2 family genes were classified into two distinct subclasses TPXLs and MAP genes WAVE DAMPENED2-LIKE ( WDLs ) and quite conservative in quantity. GhWDL3 was significantly up-regulated in 15 days post anthesis fibers of ZRI-015 (an upland cotton with longer and stronger fiber). GhWDL3 promotes all stem hairs to become straight when overexpressed in Arabidopsis , which may indirectly regulate cotton fiber cell morphology during fiber development. Virus induced gene silencing (VIGS) results showed that GhWDL3 inhibited fiber cell elongation at fiber development periods through regulating the expression of cell wall related genes. Conclusion These results reveal that GhWDL3 regulated cotton fiber cell elongation and provide crucial information for the further investigation in the regulatory mechanisms/networks of cotton fiber length.

Strigolactones (SLs) represent a new group of phytohormones that play a pivotal role in the regulation of plant shoot branching and the development of adventitious roots. In cotton (Gossypium hirsutum, Gh), SLs play a crucial role in the regulation of fiber cell elongation and secondary cell wall thickness. However, the underlying molecular mechanisms of SL signaling involved in fiber cell development are largely unknown. In this study, we report two SL-signaling genes, GhMAX2-3 and GhMAX2-6, which positively regulate cotton fiber elongation. Further protein—protein interaction and degradation assays showed that the repressor of the auxin cascade GhIAA17 serves as a substrate for the F-box E3 ligase GhMAX2. The in vivo ubiquitination assay suggested that GhMAX2-3 and GhMAX2-6 ubiquitinate GhIAA17 and coordinately degrade GhIAA17 with GhTIR1. The findings of this investigation offer valuable insights into the roles of GhMAX2-mediated SL signaling in cotton and establish a solid foundation for future endeavors aimed at optimizing cotton plant cultivation.

Optimal plant height is crucial in modern agriculture,influencing lodging resistance and facilitating mech-anized crop production.Upland cotton(Gossypium hirsutum)is the most important fiber crop globally;however,the genetic basis underlying plant height remains largely unexplored.In this study,we conducted a genome-wide association study to identify a major locus controlling plant height(PH1)in upland cotton.This locus encodes gibberellin 2-oxidase 1A(GhPH1)and features a 1133-bp structural variation(PAVPH1)located approximately 16 kb upstream.The presence or absence of PAVPH1 influences the expression of GhPH1,thereby affecting plant height.Further analysis revealed that a gibberellin-regulating transcription factor(GhGARF)recognizes and binds to a specific CATTTG motif in both the GhPH1 promoter and PAVPH1.This interaction downregulates GhPH1,indicating that PAVPH1 functions as a distant upstream silencer.Intriguingly,we found that DWARF53(D53),a key repressor of the strigolactone(SL)signaling pathway,directly interacts with GhGARF to inhibit its binding to targets.Moreover,we identified a previously unrec-ognized gibberellin-SL crosstalk mechanism mediated by the GhD53-GhGARF-GhPH1/PAVPH1 module,which is crucial for regulating plant height in upland cotton.These findings shed light on the genetic basis and gene interaction network underlying plant height,providing valuable insights for the development of semi-dwarf cotton varieties through precise modulation of GhPH1 expression.

Cotton (Gossypium) fiber length, a key trait determining fiber yield and quality, is highly regulated by a class of recently identified phytohormones, strigolactones (SLs). However, the underlying molecular mechanisms of SL signaling involved in fiber cell development are largely unknown. Here, we show that the SL signaling repressors MORE AXILLARY GROWTH2-LIKE7 (GhSMXL7) and GhSMXL8 negatively regulate cotton fiber elongation. Specifically, GhSMXL7 and GhSMXL8 inhibit the polyubiquitination and degradation of the gibberellin (GA)-triggered DELLA protein (GhSLR1). Biochemical analysis revealed that GhSMXL7 and GhSMXL8 physically interact with GhSLR1, which interferes with the association of GhSLR1 with the E3 ligase GA INSENSITIVE2 (GhGID2), leading to the repression of GA signal transduction. GhSMXL7 also interacts with the transcription factor GhHOX3, preventing its binding to the promoters of essential fiber elongation regulatory genes. Moreover, both GhSMXL7 and GhSMXL8 directly bind to the promoter regions of the AUXIN RESPONSE FACTOR (ARF) genes GhARF18-10A, GhARF18-10D, and GhARF19-7D to suppress their expression. Cotton plants in which GhARF18-10A, GhARF18-10D, and GhARF19-7D transcript levels had been reduced by virus-induced gene silencing (VIGS) displayed reduced fiber length compared with control plants. Collectively, our findings reveal a mechanism illustrating how SL integrates GA and auxin signaling to coordinately regulate plant cell elongation at the single-cell level.

Ubiquitin-conjugating enzyme (UBC) is a crucial component of the ubiquitin-proteasome system, which contributes to plant growth and development. While some UBCs have been identified as potential regulators of abiotic stress responses, the underlying mechanisms of this regulation remain poorly understood. Here, we report a cotton (Gossypium hirsutum) UBC gene, GhUBC10-2, which negatively regulates the salt stress response. We found that the gain of function of GhUBC10-2 in both Arabidopsis (Arabidopsis thaliana) and cotton leads to reduced salinity tolerance. Additionally, GhUBC10-2 interacts with glutathione S-transferase (GST) U17 (GhGSTU17), forming a heterodimeric complex that promotes GhGSTU17 degradation. Intriguingly, GhUBC10-2 can be self-polyubiquitinated, suggesting that it possesses E3-independent activity. Our findings provide new insights into the PTM of plant GST-mediated salt response pathways. Furthermore, we found that the WRKY transcription factor GhWRKY13 binds to the GhUBC10-2 promoter and suppresses its expression under salt conditions. Collectively, our study unveils a regulatory module encompassing GhWRKY13-GhUBC10-2-GhGSTU17, which orchestrates the modulation of reactive oxygen species homeostasis to enhance salt tolerance.

Drought, salinity, extreme temperatures, pathogens, and attacks by herbivores are environmental stresses that plants experience repeatedly. In order to survive in repeated stressful environments, plants have evolved a new adaptive mechanism known as ‘stress memory’. Coordinated responses of cell, gene/genome, and epigenetic modifications, including altered physiological responses, gene activation, hyper-induction and chromatin modification are considered necessary for the formation of stressed memories. Cotton ( Gossypium spp.) is an important economic crop, which can be used as raw materials in many fields and has high economic value. Here, we ensured that G. hirsutum drought memory was established after cycles of mild drought and re-watering treatment, and studied gene expression by whole-transcriptome RNA sequencing. The physiological, biochemical and molecular mechanisms of drought stress memory formation in G. hirsutum were revealed. As a histone modification, H3K4me3 plays an important role in [+/+] transcript memory. In addition, the intergenerational inheritance phenomenon of drought stress memory in G. hirsutum was also exhibited. Our results showed that the pathways of long-term and short-term memory may be different.

OVATE Family Protein(OFP)是一类植物特异性转录因子,广泛参与植物的生长发育,其在棉花中的研究尚未见报道.本研究从陆地棉NDM8基因组中共鉴定到61个GhOFP基因,系统聚类将其分为6个亚组(Clade Ⅰ,Ⅱ,Ⅲ,Ⅳ,Ⅴ和Ⅵ).转录组和qRT-PCR分析表明,棉纤维发育的起始和伸长阶段高调表达的GhOFP基因主要分布在Clade Ⅱ亚组,且该亚组的GhOFP基因启动子含有促进伸长生长的赤霉素和生长素响应的顺式元件;在棉纤维发育的次级细胞壁加厚阶段高调表达的GhOFP基因主要分布在Clade Ⅵ亚组,且该亚组的GhOFP基因启动子含有参与细胞壁生长的脱落酸、茉莉酸和水杨酸响应的顺式元件.陆地棉GhOFP基因家族的全基因组鉴定和分析将为进一步研究棉花GhOFP基因在棉纤维发育过程中的生物学功能提供参考.

Strigolactones (SLs) are a class of phytohormones that regulate plant shoot branching and adventitious root development. However, little is known regarding the role of SLs in controlling the behavior of the smallest unit of the organism, the single cell. Here, taking advantage of a classic single-cell model offered by the cotton (Gossypium hirsutum) fiber cell, we show that SLs, whose biosynthesis is fine-tuned by gibberellins (GAs), positively regulate cell elongation and cell wall thickness by promoting the biosynthesis of very long-chain fatty acids (VLCFAs) and cellulose, respectively. Furthermore, we identified two layers of transcription factors (TFs) involved in the hierarchical regulation of this GA-SL crosstalk. The top-layer TF GROWTH-REGULATING FACTOR 4 (GhGRF4) directly activates expression of the SL biosynthetic gene DWARF27 (D27) to increase SL accumulation in fiber cells and GAs induce GhGRF4 expression. SLs induce the expression of four second-layer TF genes (GhNAC100-2, GhBLH51, GhGT2, and GhB9SHZ1), which transmit SL signals downstream to two ketoacyl-CoA synthase genes (KCS) and three cellulose synthase (CesA) genes by directly activating their transcription. Finally, the KCS and CesA enzymes catalyze the biosynthesis of VLCFAs and cellulose, respectively, to regulate development of high-grade cotton fibers. In addition to providing a theoretical basis for cotton fiber improvement, our results shed light on SL signaling in plant development at the single-cell level.

Selenium (Se) is a trace mineral element in soils that can be beneficial to plants in small amounts. Although maize is among the most economically important crops, there are few reports on the effects of Se on maize seedling growth at the molecular level. In this study, the growth of maize seedlings treated with different concentrations of Na2SeO3 was investigated, and the physiological characteristics were measured. Compared with the control, a low Se concentration promoted seedling growth, whereas a high Se concentration inhibited it. To illustrate the transcriptional effects of Se on maize seedling growth, samples from control plants and those treated with low or high concentrations of Se were subjected to RNA sequencing. The differentially expressed gene (DEG) analysis revealed that there were 239 upregulated and 106 downregulated genes in the low Se treatment groups, while there were 845 upregulated and 1,686 downregulated DEGs in the high Se treatment groups. Both the Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation analyses showed a low concentration of the Se-stimulated expression of “DNA replication” and “glutathione (GSH) metabolism”-related genes. A high concentration of Se repressed the expression of auxin signal transduction and lignin biosynthesis-related genes. The real-time quantitative reverse transcription PCR (qRT-PCR) results showed that in the low Se treatment, “auxin signal transduction,” “DNA replication,” and lignin biosynthesis-related genes were upregulated 1.4- to 57.68-fold compared to the control, while, in the high Se concentration treatment, auxin signal transduction and lignin biosynthesis-related genes were downregulated 1.6- to 16.23-fold compared to the control. Based on these transcriptional differences and qRT-PCR validation, it was found that a low dosage of Se may promote maize seedling growth but becomes inhibitory to growth at higher concentrations. This study lays a foundation for the mechanisms underlying the effects of Se on maize seedling growth.

Background F-box proteins are substrate-recognition components of the Skp1-Rbx1-Cul1-F-box protein (SCF) ubiquitin ligases. By selectively targeting the key regulatory proteins or enzymes for ubiquitination and 26S proteasome mediated degradation, F-box proteins play diverse roles in plant growth/development and in the responses of plants to both environmental and endogenous signals. Studies of F-box proteins from the model plant Arabidopsis and from many additional plant species have demonstrated that they belong to a super gene family, and function across almost all aspects of the plant life cycle. However, systematic exploration of F-box family genes in the important fiber crop cotton ( Gossypium hirsutum ) has not been previously performed. The genome-wide analysis of the cotton F-box gene family is now possible thanks to the completion of several cotton genome sequencing projects. Results In current study, we first conducted a genome-wide investigation of cotton F-box family genes by reference to the published F-box protein sequences from other plant species. 592 F-box protein encoding genes were identified in the Gossypium hirsutume acc.TM-1 genome and, subsequently, we were able to present their gene structures, chromosomal locations, syntenic relationships with their parent species. In addition, duplication modes analysis showed that cotton F-box genes were distributed to 26 chromosomes, with the maximum number of genes being detected on chromosome 5. Although the WGD (whole-genome duplication) mode seems play a dominant role during cotton F-box gene expansion process, other duplication modes including TD (tandem duplication), PD (proximal duplication), and TRD (transposed duplication) also contribute significantly to the evolutionary expansion of cotton F-box genes. Collectively, these bioinformatic analysis suggest possible evolutionary forces underlying F-box gene diversification. Additionally, we also conducted analyses of gene ontology, and expression profiles in silico, allowing identification of F-box gene members potentially involved in hormone signal transduction. Conclusion The results of this study provide first insights into the Gossypium hirsutum F-box gene family, which lays the foundation for future studies of functionality, particularly those involving F-box protein family members that play a role in hormone signal transduction.