The asymmetric leaves2 ( as2 ) is a classical Arabidopsis thaliana(L.) Heynh. mutant that shows leaf lobes and leaflet like structures from the petioles of leaves. Genetic and molecular analyses have demonstrated that the AS2 function is required for repression of meristem related homeobox genes in leaves. In this study, we describe phenotypic characterizations of new as2 alleles that are in the Landsberg erecta (Ler) genetic background. In addition to the as2 phenotypes reported previously, the new as2 mutants have some leaves with petiole growth underneath the leaf blade, showing a lotus leaf structure. More severe rosettes leaves of the as2 mutants form a filament like structure, reflecting a loss of the adaxial abaxial polarity in leaves. Among as2 mutants analyzed in different genetic backgrounds, only those that are in the Ler genetic background resulted in a high frequency of the lotus leaf structure. We have isolated the AS2 gene by map based gene cloning. The predicted AS2 protein contains a leucine zipper motif, and its N terminus shares high levels of sequence similarity to those of a group of predicted proteins with no known biological functions.AS2 transcripts were detected in leaves, flowers and fruits, but absent in stems, consistent with the mutant phenotypes.
拟南芥编码亮氨酸拉链蛋白的AS2基因在叶发育中具有控制极性建立的作用
徐 轶* 孙 越* 梁婉琪 黄 海**
（中国科学院上海生命科学研究院上海植物生理生态研究所植物分子遗传国家重点实验室，上海200032）
摘要: 在拟南芥 (Arabidopsisthaliana (L .)Heynh .)叶发育研究中 ,as2是一个经典突变体。as2典型的表型是叶片开裂或形成一种小叶状结构。遗传学和分子生物学实验证明 ,AS2基因具有抑制KNOX基因在叶中表达的功能。在本文中 ,我们着重研究了新得到的在Landsbergerecta (Ler)遗传背景下的as2突变体。除了前人报道过的as2表型外 ,新as2突变体的部分叶柄长在叶片的下方 ,形成一种荷叶状结构 ,更严重的甚至长成花丝状叶结构。这两种结构都反映了不正常的叶腹背轴极性分化。在我们所收集到的as2等位突变体中 ,只有在Ler背景下这两种结构才以高频率出现。我们通过图位克隆方法分离了AS2基因。该基因编码一个含有亮氨酸拉链结构的蛋白。在拟南芥中 ,AS2同源基因共 4 3个 ,除AS2外 ,其他基因的功能都不清楚。AS2在叶和花中表达 ,在茎中无表达 ,这种表达模式和as2突变体的表型是吻合的。
关键词： 拟南芥；ASYMMETRIC LEAVESI;ASYMMETRIC LEAVES2; ERECTA;亮氨酸拉链结构；极性建立
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