Function and characterization of starch synthase I using mutants in rice
Function and characterization of starch synthase I using mutants in rice
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DOI：
10.1104/pp.105.071845
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发表时间：
2006-03-01
期刊：
影响因子：
7.4
通讯作者：
Nakamura, Y
中科院分区：
文献类型：
--
作者：
Fujita, N;Yoshida, M;Nakamura, Y
利用反转录转座子Tos 17插入产生了四个淀粉合成酶I（SSI）缺陷型水稻突变系。突变体表现出不同水平的SSI活性，并产生显著较低量的SSI蛋白，范围为野生型的0%至20%。突变体胚乳支链淀粉的聚合度（DP）8至12的链减少，DP 6至7和DP 16至19的链增加。支链淀粉链长分布的变化程度与突变体中SSI活性的降低程度呈正相关。支链淀粉结构的变化提高了胚乳淀粉的糊化温度。链长度分析的支链淀粉在SSI带切离天然聚丙烯酰胺凝胶电泳/SS活性染色凝胶显示，SSI优先合成DP 7至11链延长DP 4至7短链的糖原或支链淀粉。这些结果表明，SSI从支链淀粉的A或B-1链中的分支点出现的短DP 6至7链明显产生DP 8至12链。SSI似乎从胚乳发育的极早期到晚期发挥作用。然而，SSI的完全缺乏，尽管是一个主要的SS同工酶在发育中的胚乳，种子和淀粉颗粒的大小和形状和胚乳淀粉的结晶度没有影响，这表明其他SS酶可能是能够部分补偿SSI功能。总之，本研究强烈表明，支链淀粉链是通过SSI、SSIIa和SSIIla亚型的协调作用合成的。
Four starch synthase I (SSI)-deficient rice (Oryza sativa) mutant lines were generated using retrotransposon Tos17 insertion. The mutants exhibited different levels of SSI activities and produced significantly lower amounts of SSI protein ranging from 0% to 20% of the wild type. The mutant endosperm amylopectin showed a decrease in chains with degree of polymerization (DP) 8 to 12 and an increase in chains with DP 6 to 7 and DP 16 to 19. The degree of change in amylopectin chain-length distribution was positively correlated with the extent of decrease in SSI activity in the mutants. The structural changes in the amylopectin increased the gelatinization temperature of endosperm starch. Chain-length analysis of amylopectin in the SSI band excised from native-polyacrylamide gel electrophoresis/SS activity staining gel showed that SSI preferentially synthesized DP 7 to 11 chains by elongating DP 4 to 7 short chains of glycogen or amylopectin. These results show that SSI distinctly generates DP 8 to 12 chains from short DP 6 to 7 chains emerging from the branch point in the A or B-1 chain of amylopectin. SSI seemingly functions from the very early through the late stage of endosperm development. Yet, the complete absence of SSI, despite being a major SS isozyme in the developing endosperm, had no effect on the size and shape of seeds and starch granules and the crystallinity of endosperm starch, suggesting that other SS enzymes are probably capable of partly compensating SSI function. In summary, this study strongly suggested that amylopectin chains are synthesized by the coordinated actions of SSI, SSIIa, and SSIIIa isoforms.