Engineering starch biosynthesis for increasing rice seed weight: the role of the cytoplasmic ADP-glucose pyrophosphorylase
Engineering starch biosynthesis for increasing rice seed weight: the role of the cytoplasmic ADP-glucose pyrophosphorylase
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DOI：
10.1016/j.plantsci.2004.06.028
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发表时间：
2004-12
期刊：
影响因子：
5.2
通讯作者：
Chotipa Sakulsingharoj;Sang-Bong Choi;Seon-Kap Hwang;G. Edwards;Jennifer A. Bork;C. Meyer;J. Preiss;T. Okita
中科院分区：
文献类型：
--
作者：
Chotipa Sakulsingharoj;Sang-Bong Choi;Seon-Kap Hwang;G. Edwards;Jennifer A. Bork;C. Meyer;J. Preiss;T. Okita
ADP-葡萄糖焦磷酸化酶（ADP-glucose pyrophosphorylase，AGP 1）是淀粉生物合成的限速酶。在谷物中，操纵这种酶是种子发育期间增加淀粉产量的主要目标，作为增加库强度的手段，进而增加作物产量。将大肠杆菌glgC三重突变体（TM）基因导入水稻，并在胚乳发育过程中表达。突变的酶被靶向淀粉体或细胞质，以确定ADP-葡萄糖形成和淀粉合成的细胞内位置之间的关系。当在无机磷酸盐存在下测定以抑制内源性活性时，表达淀粉质体或细胞质AGPase-TM的转基因水稻种子显示出比未转化植物高13倍的AGEs活性水平。在Pi抑制条件下，细胞质AGEs活性升高的植物表现出14 C-蔗糖标记淀粉的增加，反过来，种子重量比对照增加（高达11%）。与此相反，转基因植物表达的淀粉体靶向AGEs活性表现出小到中度增加in 14 C-蔗糖标记率为淀粉和适度增加种子重量，或在一些情况下，减少种子重量。我们的研究结果表明，细胞内的位置有显着的影响，酶的能力，增加淀粉合成，反过来，种子重量。
ADP-glucose pyrophosphorylase (AGPase) controls a rate-limiting step in starch biosynthesis. In cereals, manipulation of this enzyme is a prime target to increase starch production during seed development as a means to increase sink strength and, in turn, crop yields. The Escherichia coli glgC triple mutant (TM) gene, which encodes a highly active and allosterically insensitive AGPase, was introduced into rice and expressed during endosperm development. The mutated enzyme was targeted to either the amyloplast or cytoplasm to determine the relationship between intracellular location of ADP-glucose formation and starch synthesis. Transgenic rice seeds expressing the amyloplast or cytoplasmic AGPase-TM showed up to 13-fold higher levels of AGPase activity compared to untransformed plants when assayed in the presence of inorganic phosphate to suppress the endogenous activity. Plants having elevated cytoplasmic AGPase activity under Pi-inhibitory conditions showed increases in14C-sucrose labeling into starch and, in turn, increases (up to 11%) in seed weight over the wt. In contrast, transgenic plants expressing the amyloplast-targeted AGPase activity showed small to moderate increases in14C-sucrose-labeling rates into starch and either a moderate increase in seed weight or, in several instances, a reduction in seed weight. Our results demonstrate that the intracellular location of AGPase has a marked effect on the capacity of the enzyme to increase starch synthesis and, in turn, seed weight.