WAXY CHLAMYDOMONAS-REINHARDTII - MONOCELLULAR ALGAL MUTANTS DEFECTIVE IN AMYLOSE BIOSYNTHESIS AND GRANULE-BOUND STARCH SYNTHASE ACTIVITY ACCUMULATE A STRUCTURALLY MODIFIED AMYLOPECTIN
WAXY CHLAMYDOMONAS-REINHARDTII - MONOCELLULAR ALGAL MUTANTS DEFECTIVE IN AMYLOSE BIOSYNTHESIS AND GRANULE-BOUND STARCH SYNTHASE ACTIVITY ACCUMULATE A STRUCTURALLY MODIFIED AMYLOPECTIN
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DOI：
10.1128/jb.174.11.3612-3620.1992
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发表时间：
1992-06-01
影响因子：
3.2
通讯作者：
BALL, S
中科院分区：
文献类型：
--
作者：
DELRUE, B;FONTAINE, T;BALL, S
对莱茵衣单胞菌细胞进行紫外诱变，筛选出直链淀粉缺陷突变体。ST-2基因的两个隐性核等位基因不仅导致了直链淀粉的消失，而且导致了部分支链淀粉的消失。颗粒结合淀粉合成酶活性在携带st-2-1或st-2-2的菌株中显著降低，这与高等植物中缺乏直链淀粉（蜡质）的胚乳突变体的情况相同。在这两个突变体中，与淀粉颗粒相关的主要76-kDa蛋白缺失或大大减少，而携带st-2-1的菌株显示了一个新的56-kDa主要蛋白。甲基化和核磁共振分析表明，野生型海藻储存多糖的结构与高等植物淀粉相同，而直链淀粉缺陷突变体保留了修饰的支链淀粉部分。因此，我们认为蜡质基因产物不仅决定了高等植物淀粉质体中胚乳储存组织中直链淀粉的合成，也决定了所有淀粉积累质体中直链淀粉和部分支链淀粉的合成。讨论了ST-2（蜡质）基因产物在颗粒结合淀粉合成酶活性方面的性质。
Amylose-defective mutants were selected after UV mutagenesis of Chlamydomonas reinhardtii cells. Two recessive nuclear alleles of the ST-2 gene led to the disappearance not only of amylose but also of a fraction of the amylopectin. Granule-bound starch synthase activities were markedly reduced in strains carrying either st-2-1 or st-2-2, as is the case for amylose-deficient (waxy) endosperm mutants of higher plants. The main 76-kDa protein associated with the starch granule was either missing or greatly diminished in both mutants, while st-2-1-carrying strains displayed a novel 56-kDa major protein. Methylation and nuclear magnetic resonance analysis of wild-type algal storage polysaccharide revealed a structure identical to that of higher-plant starch, while amylose-defective mutants retained a modified amylopectin fraction. We thus propose that the waxy gene product conditions not only the synthesis of amylose from endosperm storage tissue in higher-plant amyloplasts but also that of amylose and a fraction of amylopectin in all starch-accumulating plastids. The nature of the ST-2 (waxy) gene product with respect to the granule-bound starch synthase activities is discussed.