Pectin is a major polysaccharide component that promotes plant growth and fiber elongation in cotton. In previous studies, the galacturonosyltransferase-like (GATL) gene family has been shown to be involved in pectin synthesis. However, few studies have been performed on cotton GATL genes. Here, a total of 33, 17, and 16 GATL genes were respectively identified in Gossypium hirsutum, Gossypium raimondii, and Gossypium arboreum. In multiple plant species, phylogenetic analysis divided GATL genes into five groups named GATL-a to GATL-e, and the number of groups was found to gradually change over evolution. Whole genome duplication (WGD) and segmental duplication played a significant role in the expansion of the GATL gene family in G. hirsutum. Selection pressure analyses revealed that GATL-a and GATL-b groups underwent a great positive selection pressure during evolution. Moreover, the expression patterns revealed that most of highly expressed GhGATL genes belong to GATL-a and GATL-b groups, which have more segmental duplications and larger positive selection value, suggesting that these genes may play an important role in the evolution of cotton plants. We overexpressed GhGATL2, GhGATL9, GhGATL12, and GhGATL15 in Arabidopsis and silenced the GhGATL15 gene in cotton through a virus induced gene silencing assay (VIGS). The transgenic and VIGS lines showed significant differences in stem diameter, epidermal hair length, stamen length, seed size, and fiber length than the control plant. In addition, the pectin content test proved that the pectin was significantly increased in the transgenic lines and reduced in VIGS plants, demonstrating that GhGATL genes have similar functions and act on the pectin synthesis to regulate plant growth and fiber elongation. In summary, we performed a comprehensive analysis of GhGATL genes in G. hirsutum including evolution, structure and function, in order to better understand GhGATL genes in cotton for further studies.

中文翻译：

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Gossypium hirsutum L. GATL 基因家族的全基因组研究揭示 GhGATL 基因作用于果胶合成以调节植物生长和纤维伸长

果胶是一种主要的多糖成分，可促进棉花中的植物生长和纤维伸长。在以前的研究中，半乳糖醛酸转移酶样 (GATL) 基因家族已被证明参与果胶合成。然而，对棉花 GATL 基因的研究很少。在这里，总共在陆地棉、莱蒙棉和植物棉中分别鉴定出 33、17 和 16 个 GATL 基因。在多个植物物种中，系统发育分析将 GATL 基因分为 GATL-a 到 GATL-e 5 个组，并且发现组数随着进化而逐渐变化。全基因组重复 (WGD) 和片段重复在 G. hirsutum 中 GATL 基因家族的扩展中发挥了重要作用。选择压力分析表明，GATL-a 和 GATL-b 组在进化过程中经历了很大的正选择压力。此外，表达模式显示大部分高表达的GhGATL基因属于GATL-a和GATL-b组，具有更多的节段重复和更大的正选择值，表明这些基因可能在棉花植物的进化中发挥重要作用. 我们在拟南芥中过表达 GhGATL2、GhGATL9、GhGATL12 和 GhGATL15，并通过病毒诱导的基因沉默试验 (VIGS) 使棉花中的 GhGATL15 基因沉默。与对照植物相比，转基因和 VIGS 系在茎直径、表皮毛发长度、雄蕊长度、种子大小和纤维长度方面表现出显着差异。此外，果胶含量试验证明，转基因株系果胶含量显着增加，VIGS植株中果胶含量显着降低，表明GhGATL基因具有相似的功能，作用于果胶合成，调节植物生长和纤维伸长。总之，我们对陆地棉中的 GhGATL 基因进行了包括进化、结构和功能在内的综合分析，以更好地了解棉花中的 GhGATL 基因以进行进一步研究。