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GENETIC CHARACTERISTICS IN DETERMINING THE PRIORITY OF SPIKELETS WITHIN THE PANICLE FOR GRAIN FILLING IN RICE

确定水稻籽粒灌浆中穗内小穗优先级的遗传特征

基本信息

批准号：
16580008
负责人：
NAKAMURA Teiji
金额：
$ 2.43万
依托单位：
Tohoku University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
2004
资助国家：
日本
起止时间：
2004 至 2006
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-16580008/
关键词：
rice grain early growth grain filling priority for grain filling abscisic acid cytokinin ethylene 弱勢登熟優先度 source sink比

项目摘要

There is the genetic difference in determining the priority of spikelets within the panicle for grain filling in rice. Under the low source/sink ratio, the early growth of grains at the lower positions within the panicle (inferior grains) is easy to delay in Sasanishiki and Koshihikari, but is difficult to delay in 92133 (China) and Akinishiki. Consequently, the percentage of grain filling is lower in the former varieties than in the later varieties. The physiological mechanism which accounts for this genetic difference was investigated. Shading after heading lowered the abscisic acid (ABA) levels in the inferior grains in Sasanishiki and Koshihikari, but had no effect in 92133 (China) and Akinishiki. There was no relation between the early growth of inferior grain and its endogenous cytokinin or free sugar levels. It was known that exogenous cytokinin promotes the early grain growth and grain filling.Therefore, it was concluded that the genetic difference in determining the priority of spikelets for grain filling was regulated by the endogenous ABA levels in the grains.Generally, ABA promotes the ethylene evolution. But ABA did not change the ethylene evolution from the panicle, and some chemicals changed the ethylene evolution without the changes of the early grain growth, suggesting that ABA promote the grain growth directly.Not only ABA but also cytokinin promotes the early growth of inferior grains. In this study, exogenous cytokinin or ABA and root cutting promoted the early growth of inferior grains. Endogenous cytokinin levels in inferior grains was increased by increasing the nitrogen level, but was decreased by root cutting. Endogenous ABA level was increased by exogenous cytokinin or ABA and root cutting, and was closely related to the grain growth. These results suggest that cytokinin promotes the grain growth through the increase of the levels of endogenous ABA.

决定穗内颖花灌浆优先顺序的遗传因素存在差异。在低源库比条件下，穗下部籽粒（弱势粒）的早期生长在穗西木和越光中容易延迟，而在92133（中国）和赤西木中难以延迟。因此，前一个品种的灌浆速率低于后一个品种。对造成这种遗传差异的生理机制进行了研究。抽穗后遮光降低了Sasanishiki和Koshihikari弱势粒脱落酸（阿坝）水平，但对92133（中国）和Akinishiki没有影响。弱势粒的早期生长与其内源细胞分裂素和游离糖水平无关。已知外源细胞分裂素促进籽粒早期生长和灌浆，因此认为决定籽粒灌浆小穗优先性的遗传差异受籽粒内源阿坝水平的调节，阿坝通常促进乙烯的释放。但阿坝对穗部乙烯的释放没有影响，某些化学物质在不影响籽粒早期生长的情况下改变了穗部乙烯的释放，说明阿坝对籽粒的生长有直接的促进作用，不仅阿坝对弱势粒的早期生长有促进作用，细胞分裂素也有促进作用。本研究中，外源细胞分裂素或阿坝和断根促进弱势粒的早期生长。弱势粒内源细胞分裂素水平随施氮水平的提高而提高，但断根则降低。外源细胞分裂素或阿坝和断根均能提高内源阿坝水平，并与籽粒生长密切相关。这些结果表明，细胞分裂素通过提高内源阿坝水平促进籽粒生长。