Xu Lin, Xu Yi, Dong Aiwu, Sun Yue, Pi Limin, Xu Yuquan, Huang Hai
National Laboratory of Plant Molecular Genetics, Shanghai Institute of Plant Physiology and Ecology, Shanghai Institute for Biological Sciences, Chinese Academy of Sciences, 300 Fenglin Road, Shanghai 200032, China.
Development. 2003 Sep;130(17):4097-107. doi: 10.1242/dev.00622.
The shoot apical meristem (SAM) of seed plants is the site at which lateral organs are formed. Once organ primordia initiate from the SAM, they establish polarity along the adaxial-abaxial, proximodistal and mediolateral axes. Among these three axes, the adaxial-abaxial polarity is of primary importance in leaf patterning. In leaf development, once the adaxial-abaxial axis is established within leaf primordia, it provides cues for proper lamina growth and asymmetric development. It was reported previously that the Arabidopsis ASYMMETRIC LEAVES1 (AS1) and ASYMMETRIC LEAVES2 (AS2) genes are two key regulators of leaf polarity. In this work, we demonstrate a new function of the AS1 and AS2 genes in the establishment of adaxial-abaxial polarity by analyzing as1 and as2 alleles in the Landsberg erecta (Ler) genetic background. We provide genetic evidence that the Arabidopsis ERECTA (ER) gene is involved in the AS1-AS2 pathway to promote leaf adaxial fate. In addition, we show that AS1 and AS2 bind to each other, suggesting that AS1 and AS2 may form a complex that regulates the establishment of leaf polarity. We also report the effects on leaf polarity of overexpression of the AS1 or AS2 genes under the control of the cauliflower mosaic virus (CAMV) 35S promoter. Although plants with as1 and as2 mutations have very similar phenotypes, 35S::AS1/Ler and 35S::AS2/Ler transgenic plants showed dramatically different morphologies. A possible model of the AS1, AS2 and ER action in leaf polarity formation is discussed.
种子植物的茎尖分生组织（SAM）是侧生器官形成的部位。一旦器官原基从SAM起始，它们就会沿着近轴-远轴、近端-远端和内侧-外侧轴建立极性。在这三个轴中，近轴-远轴极性在叶片模式形成中最为重要。在叶片发育过程中，一旦在叶原基内建立了近轴-远轴轴，它就会为叶片的正常生长和不对称发育提供线索。先前有报道称，拟南芥的不对称叶1（AS1）和不对称叶2（AS2）基因是叶片极性的两个关键调节因子。在这项研究中，我们通过分析Landsberg erecta（Ler）遗传背景下的as1和as2等位基因，证明了AS1和AS2基因在近轴-远轴极性建立中的新功能。我们提供了遗传证据，表明拟南芥的ERECTA（ER）基因参与AS1-AS2途径以促进叶片近轴命运。此外，我们表明AS1和AS2相互结合，这表明AS1和AS2可能形成一个调节叶片极性建立的复合体。我们还报道了在花椰菜花叶病毒（CAMV）35S启动子控制下AS1或AS2基因过表达对叶片极性的影响。尽管具有as1和as2突变的植物具有非常相似的表型，但35S::AS1/Ler和35S::AS2/Ler转基因植物表现出显著不同的形态。本文讨论了AS1、AS2和ER在叶片极性形成中的可能作用模型。
