Plant Physiol|山东大学生科院周传恩团队揭示LMI1通过生长素转运基因SM1调控叶片边缘发育
植物叶片已经进化成不同的形状，后期分生组织识别1（LMI1）及其编码同源结构域亮氨酸拉链转录因子的同源基因被认为是植物叶片发育调控的进化热点。然而，LMI1介导的叶片形状形成的调控机制尚不清楚。
MtLMI1a和MtLMI1b是豆科模式植物Medicago truncatula中LMI1的同源基因。在这里，我们研究了MtLMI1a和MtLMI1b在叶缘形态发生中的作用。MtLMI1a和MtLMI1b沿着叶缘以一种近乎互补的模式表达，并且它们冗余地促进叶缘锯齿状突起的发育，如它们的双突变体中相对平滑的叶缘所示。此外，MtLMI1s直接激活光滑叶缘1（SLM1）的表达，SLM1编码生长素外排载体，从而调节生长素沿叶缘的分布。进一步分析表明，MtLMI1s与NO顶端分生组织（MtNAM）和ARGONAUTE7（MtAGO7）介导的反式作用短干扰rna（TAS3-ta-siRNA）途径相互作用，形成最终的叶缘形状。MtLMI1s参与生长素依赖的叶缘形成在功能保护的背景下是有趣的。
此外，尽管LMI1s在物种间具有功能等效性，但LMI1s的不同表达模式及其在关键领域内的假定的副作用是功能专门化的重要驱动因素。
Plant leaves have evolved into diverse shapes and LATE MERISTEM IDENTITY1 (LMI1) and its putative paralogous genes encode homeodomain leucine zipper transcription factors are proposed evolutionary hotspots for the regulation of leaf development in plants. However, the LMI1-mediated regulatory mechanism underlying leaf shape formation is largely unknown. MtLMI1a and MtLMI1b are putative orthologs of LMI1 in the model legume barrelclover (Medicago truncatula). Here, we investigated the role of MtLMI1a and MtLMI1b in leaf margin morphogenesis by characterizing loss-of-function mutants. MtLMI1a and MtLMI1b are expressed along leaf margin in a near-complementary pattern, and they redundantly promote development of leaf margin serrations, as revealed by the relatively smooth leaf margin in their double mutants. Moreover, MtLMI1s directly activate expression of SMOOTH LEAF MARGIN1 (SLM1), which encodes an auxin efflux carrier, thereby regulating auxin distribution along the leaf margin. Further analysis indicates that MtLMI1s genetically interact with NO APICAL MERISTEM (MtNAM) and the ARGONAUTE7 (MtAGO7)-mediated trans-acting short interfering RNA3 (TAS3 ta-siRNA) pathway to develop the final leaf margin shape. The participation of MtLMI1s in auxin-dependent leaf margin formation is interesting in the context of functional conservation. Furthermore, the diverse expression patterns of LMI1s and their putative paralogs within key domains are important drivers for functional specialization, despite their functional equivalency among species.
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