Expression of the ASYMMETRIC LEAVES2 gene in the adaxial domain of Arabidopsis leaves represses cell proliferation in this domain and is critical for the development of properly expanded leaves
Expression of the ASYMMETRIC LEAVES2 gene in the adaxial domain of Arabidopsis leaves represses cell proliferation in this domain and is critical for the development of properly expanded leaves
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DOI：
10.1111/j.1365-313x.2007.03132.x
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发表时间：
2007-07-01
期刊：
影响因子：
7.2
通讯作者：
Machida, Chiyoko
中科院分区：
文献类型：
--
作者：
Iwakawa, Hidekazu;Iwasaki, Mayumi;Machida, Chiyoko
拟南芥的 ASYMMETRIC LEAVES2 (AS2) 基因（AS2/LOB 基因家族成员）和 ASYMMETRIC LEAVES1 (AS1) 基因参与对称、扩张叶片的发育。我们在此报告这些基因的表达模式，以及此类表达位点在叶子发育中的重要性。这两个基因的转录本在早期阶段在整个叶原基中积累，但积累模式随着叶子的扩展而改变。分别在叶的近轴域和近轴域与远轴域之间的内部域中检测到 AS2 和 AS1 转录本。相应突变株系子叶中近轴细胞数与远轴细胞数的比值大于野生型子叶中的比值。在as2突变植物中，在AS1启动子控制下，AS2的低水平异位表达在某些情况下恢复了几乎正常的表型，但也导致了比野生型植物更平坦的叶子。该构建体在野生型和as2植物（而非as1植物）中的强表达导致形成狭窄、向上卷曲的叶子。我们的结果表明，在 AS1 存在的情况下，AS2 抑制近轴域的细胞增殖，并且 AS2 在适当水平的近轴表达对于对称、扩张的椎板的发育至关重要。实时RT-PCR分析显示，AS2或AS1的突变导致ETTIN（ETT；也称为AUXIN RESPONSE FACTOR3，ARF3）和KANADI2（KAN2）（它们是远轴决定簇）和YABBY5（YAB5）的转录物水平增加。因此，AS2和AS1可能负向调节这些基因在近轴域的表达，这可能与扁平和展开的叶子的发育有关。
The ASYMMETRIC LEAVES2 (AS2) gene, a member of the AS2/LOB gene family, and the ASYMMETRIC LEAVES1 (AS1) gene of Arabidopsis thaliana participate in the development of a symmetrical, expanded lamina. We report here the patterns of expression of these genes, and the importance of the sites of such expression in leaf development. Transcripts of both genes accumulated in the entire leaf primordia at early stages, but the patterns of accumulation changed as the leaves expanded. AS2 and AS1 transcripts were detected, respectively, in the adaxial domain and in the inner domain between the adaxial and abaxial domains of leaves. The ratios of numbers of adaxial cells to abaxial cells in cotyledons of corresponding mutant lines were greater than the ratios in wild-type cotyledons. The low levels of ectopic expression of AS2 under the control of the AS1 promoter in as2 mutant plants restored an almost normal phenotype in some cases, but also resulted in flatter leaves than those of wild-type plants. Strong expression of the construct in wild-type and as2 plants, but not as1 plants, resulted in the formation of narrow, upwardly curled leaves. Our results indicate that AS2 represses cell proliferation in the adaxial domain in the presence of AS1, and that adaxial expression of AS2 at an appropriate level is critical for the development of a symmetrical, expanded lamina. Real-time RT-PCR analysis revealed that mutation of either AS2 or AS1 resulted in an increase in the levels of transcripts of ETTIN (ETT; also known as AUXIN RESPONSE FACTOR3, ARF3) and KANADI2 (KAN2), which are abaxial determinants, and YABBY5 (YAB5). Thus, AS2 and AS1 might negatively regulate the expression of these genes in the adaxial domain, which might be related to the development of flat and expanded leaves.