Akiyama Takashi, Jin Shigeki
Department of Low-Temperature Science, National Agricultural Research Center for Hokkaido Region, 1 Hitsujigaoka, Toyohira-ku, Sapporo, Hokkaido 062-8555, Japan.
J Plant Physiol. 2007 May;164(5):645-54. doi: 10.1016/j.jplph.2006.04.006.
We cloned a rice cDNA encoding a putative arginine decarboxylase (ADC) protein, a key enzyme involved with putrescine (Put) biosynthesis in plants. The isolated full-length cDNA (OsADC1) contains an insert consisting of 2451 bp. The longest open reading frame within encodes a putative protein of 702 amino acids, with a calculated molecular mass of 74 kDa and an isoelectric point of 4.9. ClustalW alignment revealed that the deduced OsADC1 protein sequence shares overall 60% and 61% identity at the amino acid level with the Pisum sativum and Glycine max ADC proteins, respectively. Additionally, several OsADC1 regions exhibited striking similarity with these two other plant ADC protein sequences, including motifs characteristic of ADC proteins. Further, RNA gel blot analysis revealed markedly increased OsADC1 mRNA levels in rice seedling leaves subjected to chilling stress. Interestingly, this treatment induced a concomitant increase in free Put levels in these samples, coincident with the observed elevated OsADC1 mRNA levels. To our knowledge, this represents the first direct evidence supporting essentially chilling-specific regulation of a rice ADC gene that also potentially influences Put accumulation, a phenomenon previously noted in cold-stressed rice seedlings.
我们克隆了一个水稻cDNA，它编码一种假定的精氨酸脱羧酶（ADC）蛋白，这是植物中参与腐胺（Put）生物合成的关键酶。分离得到的全长cDNA（OsADC1）包含一个由2451 bp组成的插入片段。其中最长的开放阅读框编码一个由702个氨基酸组成的假定蛋白，计算分子量为74 kDa，等电点为4.9。ClustalW比对显示，推导的OsADC1蛋白序列在氨基酸水平上与豌豆和大豆的ADC蛋白总体一致性分别为60%和61%。此外，OsADC1的几个区域与其他两种植物ADC蛋白序列表现出显著的相似性，包括ADC蛋白的特征基序。此外，RNA凝胶印迹分析显示，遭受冷胁迫的水稻幼苗叶片中OsADC1 mRNA水平显著增加。有趣的是，这种处理导致这些样品中游离Put水平随之增加，这与观察到的OsADC1 mRNA水平升高相一致。据我们所知，这是支持水稻ADC基因基本受冷特异性调控的首个直接证据，该调控也可能影响Put积累，这是此前在冷胁迫水稻幼苗中观察到的一种现象。
