Involvement of α-Amylase Genes in Starch Degradation in Rice Leaf Sheaths at the Post-Heading Stage
Involvement of α-Amylase Genes in Starch Degradation in Rice Leaf Sheaths at the Post-Heading Stage
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DOI：
10.1626/pps.18.277
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发表时间：
2015-07-01
影响因子：
2.5
通讯作者：
Hirano, Tatsuya
中科院分区：
文献类型：
--
作者：
Sugimura, Yu;Michiyama, Hiroyasu;Hirano, Tatsuya
明确水稻抽穗后叶鞘淀粉运转的调控机制，对于了解水稻籽粒灌浆源的能力至关重要。以高产籼稻品种高成（Takanari）和标准粳稻品种日本晴（Nipponbare）抽穗后第3叶鞘淀粉含量和α-淀粉酶基因表达水平的变化为研究对象，探讨高产品种叶鞘淀粉再动员特性。从抽穗后3天开始，高成的淀粉含量下降速度比日本晴快。抽穗后12天内淀粉含量的下降，高成品种大于日本晴品种。在水稻基因组中编码α-淀粉酶的8个基因中，RAmy 24和RAmy 3C主要在抽穗后的叶鞘中表达。RAmy 2A mRNA表达量在抽穗后第9天达到峰值。特别是在高成，RAmy 2A mRNA水平迅速增加，从抽穗后3至9天。此外，抽穗后第9天，高成的α-淀粉酶活性显著高于日本晴。我们的研究结果表明，在抽穗后阶段的高成叶鞘中的淀粉的快速降解可能归因于，至少部分，由RAmy 2A转录水平的增加所引起的α-淀粉酶活性的增强。
Identifying the mechanisms regulating starch remobilization after heading in rice leaf sheaths is essential to understand the capability of the source for grain filling. In the present study, the changes in starch content and expression levels of a-amylase genes in the third leaf sheaths of Takanari, a high-yielding indica cultivar, were compared with those of Nipponbare, a standard japonica cultivar, during the post-heading stage to examine the starch remobilization characteristics in the leaf sheath of a high-yielding cultivar. Starch content in Takanari tended to decrease at a faster rate than in Nipponbare starting 3 days after heading. The decrease in starch content during 12 days after heading was greater in Takanari than in Nipponbare. Of eight genes predicted to encode a-amylase in the rice genome, RAmy24 and RAmy3C were primarily expressed in the leaf sheaths after heading. Moreover, RAmy2A mRNA level peaked at 9 days after heading in both cultivars. Particularly in Takanari, the RAmy2A mRNA levels rapidly increased from 3 to 9 days after heading. In addition, a-amylase activity was significantly higher in Takanari than in Nipponbare at 9 days after heading. Our results suggest that the rapid degradation of starch in the leaf sheaths of Takanari at the post-heading stage may be attributed, at least in part, to the enhancement of a-amylase activity caused by an increase in RAmy2A transcription level.