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Xuewen Zhang, Lihua Huang, Yan Zhao, Chao Hu, Qingquan Guo and Jianrong Chen
AUXIN BINDING PROTEIN1 (ABP1) has long been proposed as a candidate of auxin receptor to mediate auxin action in plants. It is essential for plant organ development. The function of ABP1 in the development of ramie (Boehmeria nivea L.) remains unclear. Here, we examined the role of the ABP1 gene in the development of shoot in ramie, especially in leaf venation ontogeny, by transforming ABP1 antisense construct into the plants. We showed that ABP1 expression was decreased in ABP1 antisense transgenic plantlets. The decrease of ABP1 expression led to defects in plant growth including dwarf plant, and decreased apical dominance in the intact plant. In addition, ABP1 antisense lines exhibited a serious retard of leaf development involving small and twisted leaves, sparse trichome, and a decreased cell expansion. Moreover, the decreased ABP1 expression repressed the development of leaf venation. ABP1 antisense lines developed an incomplete leaf venation, which became smaller and lacked in some leaf tissues. Though the cell arrangement was normal in midrib and lateral vein, cell size was decrease and some cell layers were missing in midrib. The abnormal phenotype of leaf venation was attributed to the decreases in cell number and size. Our data support that ABP1 is necessary for shoot growth in ramie. More importantly, it plays a key role for the development of ramie leaf venation by regulating both cell expansion and division.