BEIIb基因对稻米直链淀粉及其合成途径中相关基因的影响

BEIIb Influence the Rice Amylose and Expression of Genes Involved in Starch Biosynthesis Pathway

BEIIb基因是水稻淀粉合成的一个分支酶基因,在IR36的ae突变体中,BEIIb的缺失导致了直链淀粉的大幅度提高,同时影响了淀粉合成途径一些基因的表达。为深入探索不同直链淀粉含量品种的理化性质以及决定高直链淀粉含量的遗传因子。本研究选用了IR36及其突变体以及4份不同直链淀粉含量的水稻品种进行淀粉含量、理化性质以及淀粉合成途径相关的遗传因子的表达分析。研究发现直链淀粉含量IR36的ae突变体(30.05%)是野生型IR36(21.07%)的1.4倍,且明显高于其它品种,最低的是糯稻品种‘朝紫’(3.52%);IR36ae突变体与野生型的糊化温度也存在显著差异,且综合其他几个品种的结果发现,稻米的糊化温度与直链淀粉含量呈负相关;IR36ae突变体的胶稠度比野生型的硬,且直链淀粉含量越高的品种胶稠度越硬;IR36ae突变体的淀粉颗粒比野生型要稍大一点,且直链淀粉含量较高的品种淀粉颗粒较大;定量PCR结果表明ae突变体中BEIIb的缺失导致了Wx基因的上调,以及SSI和BEI、BEIIa的下调。且淀粉合成关键酶基因中的Wx基因(GBSSⅠ)在不同品种以及不同发育时期表达量均为最高,支链淀粉合成相关基因在低直链淀粉品种中的表达明显高于在高直链淀粉品种中的表达。BEIIb的缺失引起直链淀粉的明显提高,糊化温度的降低,淀粉颗粒的增大,以及一些淀粉合成相关基因的改变。

BEIlb gene is a branching enzyme gene in rice starch synthesis. In ae mutant of IR36, the lack of BEIIb led to a remarkable increase of amylose and also influenced the gene expression involved in starch synthesis pathways. In order to further explore the physical and chemical properties of cultivars with different amylose contents as well as the genetic factors that determined high amylose content, this study analyzed the expression of starch content, physical and chemical properties as well as the genetic factors involving in starch synthesis pathway in IR36 and its mutant and the other 4 rice varieties with different amylose contents. The study found that the amylose content of IR36ae mutant （30.05%） was 1.4 times of its wild types （21.07%） and was significantly higher than that of the other varieties. Glutinous rice varieties Asamurasaki had the lowest amylose content （3.52%） among all varieties checked. Besides, the gelatinization temperature of IR36ae mutant and wild type were significantly different and rice gelatinization temperature was negatively correlated with amylose content synthesizing the results of several other species. The gel consistency of IR36ae mutant was much stiffer than that of the wild type, and the higher the amylose content, the harder the gel consistency. The starch granule of IR36ae mutant was a little bigger than that of the wild type. Compared with other several varieties, amylose content and starch granule size were positively correlated. Q-PCR results showed that in the ae mutant, the lack of BEIIb led to up-regulation of Wx gene, and down-regulation of SSI, BEI and BEIla. Moreover, the expression of Wx gene （GBSSⅠ） in key enzyme genes of starch synthesis was the highest among different varieties and different development periods. The expression of amylopectin synthesis gene in low amylose varieties were significantly higher than that in high amylose varieties. The lack of BEIIb led to significant improvement of amylose, reduction of gelatinization temperature, increase of starch granules, and the changes of some related genes of starch synthesis.