Department of Vegetable Science, College of Horticulture, China Agricultural University, Beijing 100193, China.
Beijing Key Laboratory of Growth and Developmental Regulation for Protected Vegetable Crops, China Agricultural University, Beijing 100193, China.
Int J Mol Sci. 2023 Aug 12;24(16):12718. doi: 10.3390/ijms241612718.
Plant architecture is a major motif of plant diversity, and shoot branching patterns primarily determine the aerial architecture of plants. In this study, we identified an inbred pepper line with fewer lateral branches, 20C1734, which was free of lateral branches at the middle and upper nodes of the main stem with smooth and flat leaf axils. Successive leaf axil sections confirmed that in normal pepper plants, for either node n, P (Primordium n) < 1 cm and P < 1 cm were the critical periods between the identification of axillary meristems and the establishment of the region, whereas P < 1 cm was fully developed and formed a completely new organ. In 20C1734, the normal axillary meristematic tissue region establishment and meristematic cell identity confirmation could not be performed on the axils without axillary buds. Comparative transcriptome analysis revealed that "auxin-activated signaling pathway", "response to auxin", "response to abscisic acid", "auxin biosynthetic process", and the biosynthesis of the terms/pathways, such as "secondary metabolites", were differentially enriched in different types of leaf axils at critical periods of axillary meristem development. The accuracy of RNA-seq was verified using RT-PCR for some genes in the pathway. Several differentially expressed genes (DEGs) related to endogenous phytohormones were targeted, including several genes of the PINs family. The endogenous hormone assay showed extremely high levels of IAA and ABA in leaf axils without axillary buds. ABA content in particular was unusually high. At the same time, there is no regular change in IAA level in this type of leaf axils (normal leaf axils will be accompanied by AM formation and IAA content will be low). Based on this, we speculated that the contents of endogenous hormones IAA and ABA in 20C1734 plant increased sharply, which led to the abnormal expression of genes in related pathways, which affected the formation of Ams in leaf axils in the middle and late vegetative growth period, and finally, nodes without axillary buds and side branches appeared.
植物结构是植物多样性的主要特征，而分枝模式主要决定植物的空中结构。在这项研究中，我们鉴定了一个自交辣椒品系 20C1734，该品系在主茎的中上部节点上没有侧枝，具有光滑平坦的叶腋。连续的叶腋切片证实，在正常辣椒植株中，对于任意节点 n，P（原基 n）<1cm 和 P<1cm 是腋芽分生组织鉴定和区域建立之间的关键时期，而 P<1cm 完全发育并形成一个全新的器官。在 20C1734 中，在没有腋芽的腋芽中，正常的腋芽分生组织区域建立和分生组织细胞身份确认无法进行。比较转录组分析表明，“生长素激活信号通路”、“生长素响应”、“脱落酸响应”、“生长素生物合成过程”和“次生代谢物”等术语/途径的生物合成在腋芽发育的关键时期在不同类型的叶腋中差异富集。使用 RT-PCR 对通路中的一些基因进行了 RNA-seq 准确性验证。针对几个与内源植物激素相关的差异表达基因（DEGs），包括 PINs 家族的几个基因，进行了靶向分析。内源激素测定显示，无腋芽叶腋中的 IAA 和 ABA 含量极高。ABA 含量特别高。同时，这种叶腋（正常叶腋会伴随着 AM 的形成，IAA 含量会较低）中 IAA 水平没有规律变化。基于此，我们推测 20C1734 植株内源激素 IAA 和 ABA 含量急剧增加，导致相关途径中基因表达异常，影响了中晚营养生长期叶腋中 Ams 的形成，最终导致无腋芽节点和侧枝的出现。
