Matsumura Yoko, Iwakawa Hidekazu, Machida Yasunori, Machida Chiyoko
Plant Biology Research Center, Chubu University, 1200 Matsumoto-cho, Kasugai, Aichi 487-8501, Japan.
Plant J. 2009 May;58(3):525-37. doi: 10.1111/j.1365-313X.2009.03797.x. Epub 2009 Jan 19.
The ASYMMETRIC LEAVES2 (AS2) gene is required for the generation of the flat and symmetrical shape of the leaf lamina in Arabidopsis. AS2 encodes a plant-specific protein with an AS2/LATERAL ORGAN BOUNDARIES (AS2/LOB) domain that includes a cysteine repeat, a conserved single glycine residue and a leucine-zipper-like sequence in its amino-terminal half. The Arabidopsis genome contains 42 genes, including AS2, that encode proteins with an AS2/LOB domain in their amino-terminal halves, and these genes constitute the AS2/LOB gene family. In the present study, we cloned and characterized cDNAs that covered the putative coding regions of all members of this family, and investigated patterns of transcription systematically in Arabidopsis plants. Comparisons among amino acid sequences that had been deduced from the cloned cDNAs revealed eight groups of genes, with two or three members each, and high degrees of identity among entire amino acid sequences, suggesting that some members of the AS2/LOB family might have redundant function(s). Moreover, no member of the family exhibited significant similarity, in terms of the deduced amino acid sequence of the carboxy-terminal half, to AS2. Results of domain swapping between AS2 and other members of the family showed that the AS2/LOB domain of AS2 cannot be functionally replaced by those of other members of the family, and that only a few dissimilarities among respective amino acid residues of the AS2/LOB domain of AS2 and those of other members are important for the specific functions of AS2.
拟南芥中叶片扁平且对称的叶肉形态的形成需要不对称叶片2（ASYMMETRIC LEAVES2，AS2）基因。AS2编码一种植物特有的蛋白质，其氨基端含有一个AS2/侧向器官边界（AS2/LATERAL ORGAN BOUNDARIES，AS2/LOB）结构域，该结构域包括一个半胱氨酸重复序列、一个保守的单甘氨酸残基和一个亮氨酸拉链样序列。拟南芥基因组包含42个基因，包括AS2，这些基因在其氨基端编码含有AS2/LOB结构域的蛋白质，这些基因构成了AS2/LOB基因家族。在本研究中，我们克隆并鉴定了覆盖该家族所有成员推定编码区的cDNA，并系统地研究了拟南芥植株中的转录模式。从克隆的cDNA推导的氨基酸序列比较揭示了八组基因，每组有两到三个成员，并且整个氨基酸序列之间具有高度的同一性，这表明AS2/LOB家族的一些成员可能具有冗余功能。此外，就羧基端的推导氨基酸序列而言，该家族没有成员与AS2表现出显著的相似性。AS2与该家族其他成员之间的结构域交换结果表明，AS2的AS2/LOB结构域不能被该家族其他成员的结构域功能替代，并且AS2的AS2/LOB结构域与其他成员的相应氨基酸残基之间只有少数差异对AS2的特定功能很重要。
