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PLOS Genetics：水稻OsWOX4基因作用于叶片早期发育调控

已有 4473 次阅读 2018-4-28 14:59 |个人分类:每日摘要|系统分类:论文交流

WUSCHEL-RELATED HOMEOBOX4 acts as a key regulator in early leaf development in rice

First author: Yukiko Yasui; Affiliations: The University of Tokyo (东京大学): Tokyo, Japan

Corresponding author: Hiro-Yuki Hirano

Rice (Oryza sativa) has long and narrow leaves with parallel veins (叶脉), similar to other grasses. Relative to Arabidopsis thaliana which has oval-shaped (椭圆形的) leaves, our understanding of the mechanism of leaf development is insufficient in grasses. In this study, we show that OsWOX4, a member of the WUSCHEL-RELATED HOMEOBOX gene family, plays important roles in early leaf development in rice. Inducible downregulation of OsWOX4 resulted in severe defects in leaf development, such as an arrest (停止) of vascular differentiation (维管组织的分化), a partial defect in the early cell proliferation required for midrib formation (中脉形成), and a failure to maintain cellular activity in general parenchyma cells (薄壁细胞). In situ analysis (原位分析) showed that knockdown of OsWOX4 reduced the expression of two LONELY GUY genes, which function in the synthesis of active cytokinin, in developing vascular bundles (维管束). Consistent with this, cytokinin levels were downregulated by OsWOX4 knockdown. Transcriptome analysis further showed that OsWOX4 regulates multiple genes, including those responsible for cell cycle progression and hormone action, consistent with the effects of OsWOX4 downregulation on leaf phenotypes. Collectively, these results suggest that OsWOX4 acts as a key regulator at an early stage of leaf development. Our previous work revealed that OsWOX4 is involved in the maintenance of shoot apical meristem in rice, whereas AtWOX4 is specifically associated with the maintenance of vascular stem cells in Arabidopsis. Thus, the function of the two orthologous genes seems to be diversified between rice and Arabidopsis.

水稻与其他草本一样具有长而窄的叶子，叶片上带有平行的叶脉。相对于拟南芥椭圆形的的叶子，我们对于水稻叶片发育的分子机制了解得还很少，本文的研究显示WUSCHEL-RELATED HOMEOBOX基因家族的一员OsWOX4在水稻叶片早起发育过程中扮演重要作用。OsWOX4的下调表达会导致叶片发育缺陷，包括维管组织分化的停止、对于中脉形成非常重要的早期细胞增殖的部分缺陷以及薄壁细胞中细胞活性的缺失。原位分析显示OsWOX4的敲低会减少两个LONELY GUY基因的表达，其作用于发育维管束中活性细胞分裂素的生物合成。与其一致的是，细胞分裂素水平在OsWOX4敲低植株中被下调。转录组分析进一步显示OsWOX4调控了多个基因的表达，包括细胞周期和激素活性相关的基因，这与OsWOX4下调所导致的叶片表型特征一致。综上，本文的结果揭示了OsWOX4基因作为水稻叶片早期发育的关键调控因子。本文作者先前的工作显示水稻的OsWOX4基因主要作用于茎尖分生组织的维持，而拟南芥AtWOX4基因特异与维管干细胞的维持相关。因此，作者推测这两个直系同源基因在水稻和拟南芥之间已经发生了功能分化。