Regulation of betaine synthesis by precursor supply and choline monooxygenase expression in Amaranthus tricolor
Regulation of betaine synthesis by precursor supply and choline monooxygenase expression in Amaranthus tricolor
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DOI：
10.1093/jxb/erm278
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发表时间：
2007-01-01
影响因子：
6.9
通讯作者：
Takabe, Teruhiro
中科院分区：
文献类型：
--
作者：
Bhuiyan, Nazmul H.;Hamada, Akira;Takabe, Teruhiro
甜菜碱是植物在非生物胁迫下通过胆碱氧化合成的，胆碱单加氧酶（CMO）是其中的关键酶。虽然人们一直认为，甜菜碱的合成受到很好的调节，以保护非生物胁迫，它在这里显示，外源供应的前体，如胆碱，丝氨酸，甘氨酸在甜菜碱积累植物三色苋进一步提高甜菜碱的积累盐胁迫下，但不是在正常条件下。甘氨酸脱羧酶抑制剂异烟酸酰肼的加入抑制了盐诱导甜菜碱的积累。盐诱导A.三色CMO（AmCMO）和甜菜碱在根中比在叶中慢得多，并且观察到在根中脯氨酸的瞬时积累。AmCMO反义表达抑制了盐诱导的AmCMO和甜菜碱的积累，但增加了胆碱水平约2- 3倍。这表明甜菜碱合成受AmCMO表达的高度调节。分离AmCMO基因组DNA，包括上游区（1.6kbp）。AmCMO启动子区的缺失分析显示，翻译起始密码子上游的410 bp片段包含响应于盐胁迫的序列。这些数据表明，CMO的启动子序列，除了前体供应，是重要的甜菜碱积累植物A中的甜菜碱的积累。三色。
In plants, betaine is synthesized upon abiotic stress via choline oxidation, in which choline monooxygenase (CMO) is a key enzyme. Although it had been thought that betaine synthesis is well regulated to protect abiotic stress, it is shown here that an exogenous supply of precursors such as choline, serine, and glycine in the betaine-accumulating plant Amaranthus tricolor further enhances the accumulation of betaine under salt stress, but not under normal conditions. Addition of isonicotinic acid hydrazide, an inhibitor of glycine decarboxylase, inhibited the salinity-induced accumulation of betaine. Salt-induced accumulation of A. tricolor CMO (AmCMO) and betaine was much slower in roots than in leaves, and a transient accumulation of proline was observed in the roots. Antisense expression of AmCMO mRNA suppressed the salt-induced accumulation of AmCMO and betaine, but increased the level of choline similar to 2- 3-fold. This indicates that betaine synthesis is highly regulated by AmCMO expression. The genomic DNA, including the upstream region (1.6 kbp), of AmCMO was isolated. Deletion analysis of the AmCMO promoter region revealed that the 410 bp fragment upstream of the translation start codon contains the sequence responsive to salt stress. These data reveal that the promoter sequence of CMO, in addition to precursor supply, is important for the accumulation of betaine in the betaine-accumulating plant A. tricolor.