Xiong Yuanyuan, Wu Binbin, Du Fei, Guo Xiaolu, Tian Caihuan, Hu Jinrong, Lü Shouqin, Long Mian, Zhang Lei, Wang Ying, Jiao Yuling
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, the Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China; College of Life Sciences, University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Plant Genomics and National Center for Plant Gene Research (Beijing), Institute of Genetics and Developmental Biology, the Innovative Academy of Seed Design, Chinese Academy of Sciences, Beijing 100101, China.
Mol Plant. 2021 Jun 7;14(6):949-962. doi: 10.1016/j.molp.2021.03.011. Epub 2021 Mar 12.
Leaf shape is highly variable within and among plant species, ranging from slender to oval shaped. This is largely determined by the proximodistal axis of growth. However, little is known about how proximal-distal growth is controlled to determine leaf shape. Here, we show that Arabidopsis leaf and sepal proximodistal growth is tuned by two phytohormones. Two class A AUXIN RESPONSE FACTORs (ARFs), ARF6 and ARF8, activate the transcription of DWARF4, which encodes a key brassinosteroid (BR) biosynthetic enzyme. At the cellular level, the phytohormones promote more directional cell expansion along the proximodistal axis, as well as final cell sizes. BRs promote the demethyl-esterification of cell wall pectins, leading to isotropic in-plane cell wall loosening. Notably, numerical simulation showed that isotropic cell wall loosening could lead to directional cell and organ growth along the proximodistal axis. Taken together, we show that auxin acts through biosynthesis of BRs to determine cell wall mechanics and directional cell growth to generate leaves of variable roundness.
叶片形状在植物物种内部和物种之间具有高度变异性，从细长形到椭圆形不等。这在很大程度上由近远轴生长决定。然而，关于近远轴生长如何被调控以决定叶片形状，人们了解甚少。在此，我们表明拟南芥叶片和萼片的近远轴生长受两种植物激素调节。两个A类生长素响应因子（ARF），即ARF6和ARF8，激活DWARF4的转录，DWARF4编码一种关键的油菜素内酯（BR）生物合成酶。在细胞水平上，这些植物激素促进细胞沿近远轴进行更具方向性的扩展以及最终的细胞大小。油菜素内酯促进细胞壁果胶的去甲基酯化，导致细胞壁在平面内各向同性松弛。值得注意的是，数值模拟表明各向同性的细胞壁松弛可导致细胞和器官沿近远轴进行方向性生长。综上所述，我们表明生长素通过油菜素内酯的生物合成来决定细胞壁力学和方向性细胞生长，从而产生具有不同圆度的叶片。
