Brassinosteroids (BRs), an efficient plant endogenous hormone, significantly promotes plant nutrient growth adapting to biological and abiotic adversities. BRs mainly promote plant cell elongation by regulating gene expression patterns. EXORDIUM (EXO) genes have been characterized as the indicators of BR response genes. Cotton, an ancient crop, is of great economic value and its fibers can be made into all kinds of fabrics. However, EXO gene family genes have not been full identified in cotton. 175 EXO genes were identified in nine plant species, of which 39 GhEXO genes in Gossypium hirsutum in our study. A phylogenetic analysis grouped all of the proteins encoded by the EXO genes into five major clades. Sequence identification of conserved amino acid residues among monocotyledonous and dicotyledonous species showed a high level of conservation across the N and C terminal regions. Only 25% the GhEXO genes contain introns besides conserved gene structure and protein motifs distribution. The 39 GhEXO genes were unevenly distributed on the 18 At and Dt sub-genome chromosomes. Most of the GhEXO genes were derived from gene duplication events, while only three genes showed evidence of tandem duplication. Homologous locus relationships showed that 15 GhEXO genes are located on collinear blocks and that all orthologous/paralogous gene pairs had Ka > Ks values, indicating purifying selection pressure. The GhEXO genes showed ubiquitous expression in all eight tested cotton tissues and following exposure to three phytohormones, IAA, GA, and BL. Furthermore, GhEXO7_At was mainly expressed in response to BL treatment, and was predominantly expressed in the fibers. GhEXO7_At was found to be a plasma membrane protein, and its ectopic expression in Arabidopsis mediated BR-regulated plant growth and development with altered expression of DWF4, CPD, KCS1, and EXP5. Additionally, the functions of GhEXO7_At were confirmed by virus-induced gene silencing (VIGS) in cotton. This study will provide important genetic resources for future cotton breeding programs.

油菜素类固醇 (BRs) 是一种有效的植物内源性激素，可显着促进植物营养生长以适应生物和非生物逆境。BRs 主要通过调节基因表达模式促进植物细胞伸长。异端 (EXO) 基因已被表征为 BR 反应基因的指标。棉花是一种古老的作物，具有很高的经济价值，其纤维可制成各种织物。然而，EXO基因家族基因在棉花中尚未完全鉴定。175EXO 在 9 种植物中鉴定出基因，其中 39 GhEXO 基因 陆地棉在我们的研究中。系统发育分析将所有由EXO基因分为五个主要进化枝。单子叶和双子叶物种中保守氨基酸残基的序列鉴定显示在 N 和 C 末端区域具有高度的保守性。只有 25%GhEXO除了保守的基因结构和蛋白质基序分布外，基因还包含内含子。39GhEXO基因在 18 个 At 和 Dt 亚基因组染色体上分布不均。大部分的GhEXO基因来自基因复制事件，而只有三个基因显示出串联复制的证据。同源基因座关系表明，15GhEXO 基因位于共线块上，并且所有直系同源/旁系同源基因对都具有 K a > KS值，表示净化选择压力。这GhEXO基因在所有 8 个测试的棉花组织中均表现出普遍表达，并且在暴露于三种植物激素 IAA、GA 和 BL 后。此外，GhEXO7_At 主要响应于 BL 处理而表达，并且主要在纤维中表达。 GhEXO7_At 被发现是一种质膜蛋白，其异位表达 拟南芥 介导 BR 调节的植物生长和发育，具有改变的表达 DWF4, 持续专业发展, KCS1， 和 经验值5. 此外，以下功能GhEXO7_At棉花病毒诱导基因沉默 (VIGS) 证实了这一点。该研究将为未来的棉花育种计划提供重要的遗传资源。