背景:GLABRA3(GL3)和GLABRA3(EGL3)基因编码典型的螺旋-环-螺旋(bHLH)转录因子,主要调节毛状体分支和根毛发育,DNA内复制,三原虫大小,和气孔形成。棉花作物中GL3基因的功能特征很少。在这项研究中,我们对GL3和EGL3同源物进行了全面的全基因组扫描,以增强我们对它们在棉花作物毛状体和纤维发育中的潜在作用的理解.
结果:我们的发现表明,陆地棉和G.barbadense各有6个GL3,不均匀地分布在4条染色体上,G.Arboreum,G.raimondii每个有3个GL3,不均匀地分布在2条染色体上。Gh_A08G2088和Gb_A09G2187,尽管与其他GL3基因具有相同的bHLH结构域,由于明显的短序列和有限的基序数量而被排除在外,表明缺乏潜在的功能活动。系统发育分析将剩余的16个GL3分类为与拟南芥密切相关的三个亚家族(I-III组)。16个GL3具有完整的bHLH域,包含590-631个氨基酸,分子量(MWs)为65.92-71.36kDa。在描绘的每个亚家族GL3s中,共有相似的基因结构和基序,表明各组内的保守特征。启动子区分析显示27个顺式作用元件,这些元素对水杨酸有反应,脱落酸(ABA),茉莉酸甲酯(MeJA),还有赤霉素.使用公开可获得的RNA-seq数据分析了G.barbadense和G.hirsutum的12个组织中GL3基因的表达。在GL3中,Gb_D11G0219,Gb_D11G0214和Gb_D08G2182被鉴定为在不同组织中相对高表达,因此选择用于G.barbadense的激素治疗和表达验证。RT-qPCR结果显示MeJA后Gb_D11G0219和Gb_D11G0214的表达水平显著改变,GA,和ABA处理。亚细胞定位预测显示,大多数GL3蛋白主要在细胞核中表达,而少数定位于细胞质和叶绿体中。
结论:总之,本研究通过确定棉花毛状体形成和纤维发育中的激素调节模式和可能的作用位点,为后续GL3基因的功能验证奠定了基础。该结果为阐明GL3基因在棉纤维和毛状体发育的复杂过程中的作用和调控机制提供了依据。
BACKGROUND: GLABRA3 (GL3) and ENHANCER OF GLABRA3 (EGL3) genes encode a typical helix-loop-helix (bHLH) transcription factors that primarily regulate
trichome branching and root hair development, DNA endoreduplication, trichoblast size, and stomatal formation. The functions of GL3 genes in cotton crop have been poorly characterized. In this study, we performed comprehensive genome-wide scans for GL3 and EGL3 homologs to enhance our comprehension of their potential roles in
trichome and fiber development in cotton crop.
RESULTS: Our findings paraded that Gossypium hirsutum and G. barbadense have 6 GL3s each, unevenly distributed on 4 chromosomes whereas, G. arboreum, and G. raimondii have 3 GL3s each, unevenly distributed on 2 chromosomes. Gh_A08G2088 and Gb_A09G2187, despite having the same bHLH domain as the other GL3 genes, were excluded due to remarkable short sequences and limited number of motifs, indicating a lack of potential functional activity. The phylogenetic analysis categorized remaining 16 GL3s into three subfamilies (Group I-III) closely related to A. thaliana. The 16 GL3s have complete bHLH domain, encompassing 590-631 amino acids, with molecular weights (MWs) ranging from 65.92 to 71.36 kDa. Within each subfamily GL3s depicted shared similar gene structures and motifs, indicating conserved characteristics within respective groups. Promoter region analysis revealed 27 cis-acting elements, these elements were responsive to salicylic acid, abscisic acid (ABA), methyl jasmonate (MeJA), and gibberellin. The expression of GL3 genes was analyzed across 12 tissues in both G. barbadense and G. hirsutum using the publicly available RNA-seq data. Among GL3s, Gb_D11G0219, Gb_D11G0214, and Gb_D08G2182, were identified as relatively highly expressed across different tissues, consequently selected for hormone treatment and expression validation in G. barbadense. RT-qPCR results demonstrated significant alterations in the expression levels of Gb_D11G0219 and Gb_D11G0214 following MeJA, GA, and ABA treatment. Subcellular localization prediction revealed that most GL3 proteins were predominantly expressed in the nucleus, while a few were localized in the cytoplasm and chloroplasts.
CONCLUSIONS: In summary, this study lays the foundation for subsequent functional validation of GL3 genes by identifying hormonal regulation patterns and probable sites of action in cotton
trichome formation and fiber development. The results stipulate a rationale to elucidate the roles and regulatory mechanisms of GL3 genes in the intricate process of cotton fibre and
trichome development.