Characterization of SSIIIa-Deficient mutants of rice: The function of SSIIIa and pleiotropic effects by SSIIIa deficiency in the rice endosperm
Characterization of SSIIIa-Deficient mutants of rice: The function of SSIIIa and pleiotropic effects by SSIIIa deficiency in the rice endosperm
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DOI：
10.1104/pp.107.102533
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发表时间：
2007-08-01
期刊：
影响因子：
7.4
通讯作者：
Nakamura, Yasunori
中科院分区：
文献类型：
--
作者：
Fujita, Naoko;Yoshida, Mayumi;Nakamura, Yasunori
利用反转录转座子插入和化学诱变技术获得了淀粉合成酶IIIa（SSIIIa）缺陷型水稻突变体。在含糖原的天然聚丙烯酰胺凝胶上的最低迁移SS活性条带被鉴定为SSIIIa的条带，在这些突变体中完全不存在，表明它们是SSIIIa无效突变体。聚合度（DP）>= 30的支链淀粉B 2至B 4链和突变体中支链淀粉的M-r分别降低到野生型值的约60%和70%，表明SSIIIa在支链淀粉B 2至B 4链的延伸中起重要作用。在突变体支链淀粉中，DP 6至9和DP 16至19的链减少，而DP 10至15和DP 20至25的链增加。这些变化在SSIIIa突变体几乎是相反的图像的SSI-缺乏水稻突变体，并引起突变体胚乳中的SSI的量增加1.3- 1.7倍。此外，直链淀粉含量和支链淀粉的外链（DP >= 500）分别增加了1.3倍和12倍。突变体淀粉组成的这些变化是由颗粒结合淀粉合成酶（GBSSI）的量增加1.4至1.7倍引起的。突变体淀粉颗粒较小，呈圆形，结晶度较低。因此，缺乏SSIIIa，第二个主要的SS同工酶在发育中的水稻胚乳影响支链淀粉的结构，淀粉酶含量，和淀粉颗粒的理化性质在两个方面：直接通过SSIIIa缺乏本身和间接的增强SSI和GBSSI基因转录本。
Starch synthase IIIa (SSIIIa)-deficient rice ( Oryza sativa) mutants were generated using retrotransposon insertion and chemical mutagenesis. The lowest migrating SS activity bands on glycogen-containing native polyacrylamide gel, which were identified to be those for SSIIIa, were completely absent in these mutants, indicating that they are SSIIIa null mutants. The amylopectin B 2 to B 4 chains with degree of polymerization (DP) >= 30 and the M-r of amylopectin in the mutant were reduced to about 60% and 70% of the wild-type values, respectively, suggesting that SSIIIa plays an important part in the elongation of amylopectin B 2 to B 4 chains. Chains with DP 6 to 9 and DP 16 to 19 decreased while chains with DP 10 to 15 and DP 20 to 25 increased in the mutants amylopectin. These changes in the SSIIIa mutants are almost opposite images of those of SSI-deficient rice mutant and were caused by 1.3- to 1.7-fold increase of the amount of SSI in the mutants endosperm. Furthermore, the amylose content and the extralong chains (DP >= 500) of amylopectin were increased by 1.3- and 12-fold, respectively. These changes in the composition in the mutants starch were caused by 1.4- to 1.7-fold increase in amounts of granules-bound starch synthase ( GBSSI). The starch granules of the mutants were smaller with round shape, and were less crystalline. Thus, deficiency in SSIIIa, the second major SS isozyme in developing rice endosperm affected the structure of amylopectin, amylase content, and physicochemical properties of starch granules in two ways: directly by the SSIIIa deficiency itself and indirectly by the enhancement of both SSI and GBSSI gene transcripts.