Effects of on the Structure and Physicochemical Properties of Starch in Developing Rice Seeds.

Overexpression of a constitutively active truncated form of () in rice produced smaller seeds, but a double-stranded RNA gene-silenced form of () yielded larger seeds, suggesting that plays a functional role in rice seed development. In the study presented here, we propose a model in which plays key roles in negatively controlling the grain size, amylose content, and endosperm appearance, and also affects the physicochemical properties of the starch. The dehulled transgenic grains were smaller than the dehulled wild-type grains, and the endosperm was opaque and had a low amylose content and numerous small loosely packed polyhedral starch granules. However, the grain sizes and endosperm appearances were not affected by temperature, which ranged from low (22 °C) to high (31 °C) during the grain-filling phase. In contrast, the transgenic grains were larger, had higher amylose content, and had more transparent endosperms filled with tightly packed polyhedral starch granules. This demonstrates that plays a novel functional role in starch biosynthesis during seed development and affects the transparent appearance of the endosperm. These results improve our understanding of the molecular mechanisms through which the grain-filling process occurs in rice.