Plant J: 浙江大学海南学院曹家树团队与合作者共同揭示多聚半乳糖醛酸酶45参与叶片弯曲器官形态调控
调节植物结构是当前育种计划的主要目标。以前的研究增加了我们对植物结构的遗传调控的理解，但是了解器官形态是如何在细胞水平上被控制的也是很有必要的。在细胞壁中，果胶的修饰和降解是器官形态发生所必需的，这些过程涉及一系列果胶修饰酶。
多聚半乳糖醛酸酶（PGs）是一类主要的果胶水解酶，能分解果胶骨架并释放低聚半乳糖醛酸（OGs）。PG基因在植物细胞的扩增和分离中起着重要的作用，参与植物器官的扩增、分离和开裂。然而，它们是否以及如何影响其他细胞过程和器官的形态发生尚不清楚。
本研究，我们利用遗传、发育、细胞生物学和生物化学分析来描述拟南芥PG45（PG45）在器官形态发生中的功能。PG45的一个异源表达部分在体外裂解果胶高半乳糖醛酸，表明PG45是一个真正的PG。PG45在叶片和花的结构，分枝形成和器官生长中起作用。pg45基因敲除和pg45过表达叶片的波动伴随着近轴-远轴极性受损，pg45的缺失缩短了发育叶片近轴表皮细胞增殖的持续时间。在pg45基因敲除和pg45过表达的叶片中，异常的叶片弯曲与果胶代谢和自生OG谱的改变相结合。总之，这些结果强调了PGs在决定组织极性和调节细胞增殖方面先前未被充分认识的功能，并暗示了存在基于OG的调节植物发育的信号通路。
Regulating plant architecture is a major goal in current breeding programs. Previous studies have increased our understanding of the genetic regulation of plant architecture, but it is also essential to understand how organ morphology is controlled at the cellular level. In the cell wall, pectin modification and degradation are required for organ morphogenesis, and these processes involve a series of pectin-modifying enzymes. Polygalacturonases (PGs) are a major group of pectin-hydrolyzing enzymes that cleave pectin backbones and release oligogalacturonides (OGs). PG genes function in cell expansion and separation, and contribute to organ expansion, separation and dehiscence in plants. However, whether and how they influence other cellular processes and organ morphogenesis are poorly understood. Here, we characterized the functions of Arabidopsis PG45 (PG45) in organ morphogenesis using genetic, developmental, cell biological and biochemical analyses. A heterologously expressed portion of PG45 cleaves pectic homogalacturonan in vitro, indicating that PG45 is a bona fide PG. PG45 functions in leaf and flower structure, branch formation and organ growth. Undulation in pg45 knockout and PG45 overexpression leaves is accompanied by impaired adaxial–abaxial polarity, and loss of PG45 shortens the duration of cell proliferation in the adaxial epidermis of developing leaves. Abnormal leaf curvature is coupled with altered pectin metabolism and autogenous OG profiles in pg45 knockout and PG45 overexpression leaves. Together, these results highlight a previously underappreciated function for PGs in determining tissue polarity and regulating cell proliferation, and imply the existence of OG-based signaling pathways that modulate plant development.
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