As a group of plant-specific proteins, OVATE family protein (OFP) members have been shown to function as transcriptional repressors and involve in plant growth regulation in Arabidopsis and rice. It has also been shown that OFPs can interact with TONNEAU1 Recruiting Motif (TRM) proteins to regulate tomato fruit shape. In this study, we show that mutant plants with knock-down expression of OFP1, OFP2, OFP3, and OFP5 exhibit longer hypocotyls and cotyledons due to enhanced cell elongation. Overexpression of OFPs disturb the arrangement of cortical microtubule arrays in pavement cells and promote abnormal pavement cell expansion perpendicular to the direction of petiole growth, resulting in the kidney-shaped cotyledons in transgenic plants. OFP2 and OFP5 interact directly with the microtubule regulating protein TONNEAU2 (TON2), and genetic analysis suggests TON2 is required for the function of OFPs. We also show that altering the expression of OFPs affects light and BR regulated microtubule reorientation. BR treatment reduce the protein accumulation of OFP2, suggesting OFP2 mediates BR regulated microtubule reorientation. Taken together, our study provides evidences showing that OFP family proteins negatively regulate cell expansion by modulating microtubule reorganization, which requires the function of TON2.

中文翻译：

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AtOFPs 通过与 TONNEAU2 的直接相互作用调节微管方向来调节细胞伸长

作为一组植物特异性蛋白质，OVATE 家族蛋白 (OFP) 成员已被证明可作为转录抑制因子并参与拟南芥和水稻的植物生长调节。还表明，OFP 可以与 TONNEAU1 Recruiting Motif (TRM) 蛋白相互作用以调节番茄果实形状。在这项研究中，我们表明，由于细胞伸长增强，OFP1、OFP2、OFP3 和 OFP5 表达下调的突变植物表现出更长的下胚轴和子叶。OFPs的过表达扰乱了铺路细胞中皮层微管阵列的排列，促进了与叶柄生长方向垂直的铺路细胞异常扩张，导致转基因植物出现肾形子叶。OFP2 和 OFP5 直接与微管调节蛋白 TONNEAU2 (TON2) 相互作用，遗传分析表明 TON2 是 OFP 功能所必需的。我们还表明，改变 OFP 的表达会影响光和 BR 调节的微管重新定向。BR 处理减少了 OFP2 的蛋白质积累，表明 OFP2 介导了 BR 调节的微管重新定向。综上所述，我们的研究提供的证据表明，OFP 家族蛋白通过调节微管重组负向调节细胞扩张，这需要 TON2 的功能。