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首页> 外文期刊>Journal of Experimental Botany >Integrated functions among multiple starch synthases determine both amylopectin chain length and branch linkage location in Arabidopsis leaf starch
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Integrated functions among multiple starch synthases determine both amylopectin chain length and branch linkage location in Arabidopsis leaf starch

机译：多种淀粉合成酶之间的整合功能决定了拟南芥叶片淀粉中支链淀粉的链长和分支键的位置

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This study assessed the impact on starch metabolism in Arabidopsis leaves of simultaneously eliminating multiple soluble starch synthases (SS) from among SS1, SS2, and SS3. Double mutant ss1- ss2- or ss1- ss3- lines were generated using confirmed null mutations. These were compared to the wild type, each single mutant, and ss1- ss2- ss3- triple mutant lines grown in standardized environments. Double mutant plants developed similarly to the wild type, although they accumulated less leaf starch in both short-day and long-day diurnal cycles. Despite the reduced levels in the double mutants, lines containing only SS2 and SS4, or SS3 and SS4, are able to produce substantial amounts of starch granules. In both double mutants the residual starch was structurally modified including higher ratios of amylose:amylopectin, altered glucan chain length distribution within amylopectin, abnormal granule morphology, and altered placement of α(1→6) branch linkages relative to the reducing end of each linear chain. The data demonstrate that SS activity affects not only chain elongation but also the net result of branch placement accomplished by the balanced activities of starch branching enzymes and starch debranching enzymes. SS3 was shown partially to overlap in function with SS1 for the generation of short glucan chains within amylopectin. Compensatory functions that, in some instances, allow continued residual starch production in the absence of specific SS classes were identified, probaby accomplished by the granule bound starch synthase GBSS1.
机译：这项研究评估了同时消除SS1，SS2和SS3中的多种可溶性淀粉合成酶（SS）对拟南芥叶片中淀粉代谢的影响。使用证实的无效突变产生双突变体ss1-ss2-或ss1-ss3-系。将这些与野生型，每个单个突变体以及在标准化环境中生长的ss1- ss2- ss3-三重突变株进行比较。双突变植物的生长与野生型相似，尽管它们在短日和长日昼夜周期中积累的叶片淀粉较少。尽管双突变体中的水平降低，但是仅包含SS2和SS4或SS3和SS4的品系能够产生大量的淀粉颗粒。在两个双突变体中，残余淀粉都经过结构修饰，包括更高比例的直链淀粉：支链淀粉，支链淀粉内改变的葡聚糖链长分布，异常的颗粒形态以及相对于每个线性还原末端的α（1→6）分支键的位置改变链。数据表明SS活性不仅影响链延长，而且影响淀粉支化酶和淀粉脱支酶的平衡活性所完成的分支位置的净结果。显示SS3在功能上与SS1部分重叠，以产生支链淀粉内的短葡聚糖链。鉴定了在某些情况下允许在不存在特定SS类的情况下继续产生残留淀粉的补偿功能，这种可能性是由颗粒结合的淀粉合酶GBSS1完成的。

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