著者

Hayashi Mari Kodama Momoko Nakamura Yasunori Fujita Naoko

出版者

The Japanese Society of Applied Glycoscience

雑誌

Journal of Applied Glycoscience (ISSN:13447882)

巻号頁・発行日

2015

被引用文献数

16

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Starch is glucose polymer linked by α-1,4 and α-1,6 glucosidic bonds. The balance of activity between starch synthases (SSs) and branching enzymes (BEs) is important for formation of amylopectin structure. SSI and SSIIIa isozymes account for 60% and 30%, respectively, of soluble SS activity in developing rice endosperm. Complete loss of both SSI and SSIIIa activities induces sterility. By contrast, a double mutant (<i>ss1^L/ss3a</i>) generated by crossing the leaky <i>ss1</i> mutant, whose SS activity is approximately ca. 16% of the wild type, and the <i>ss3a</i> null mutant is fertile. Although there is only a significant residual SS activity in the developing endosperm of <i>ss1^L/ss3a</i>, the yield and growth of the double-mutant line is sufficient. We analyzed the amylopectin chain-length distribution, thermal and pasting properties, morphologies of starch granules and amyloplasts, and crystallinity of endosperm starch in <i>ss1^L/ss3a</i> and the parental mutant lines. The chain-length distribution pattern of <i>ss1^L/ss3a</i> was similar to that of <i>ss3a</i> and there was an additive effect of the reduction of SSI activity on the chain-length of amylopectin in the <i>ss3a</i> background. These changes in the amylopectin chain-length distribution were considered to increase the gelatinization temperature of the starch. The gelatinized starch viscosity of the double-mutant and <i>ss3a</i> lines was very low. Most <i>ss1^L/ss3a</i> starch granules were round-shaped, and the starch granular size was smaller than those of the parental mutant lines and the wild type. The starch crystallinity of <i>ss1^L/ss3a</i> was slightly reduced compared with that of the wild type.