Starch granule initiation is controlled by a heteromultimeric isoamylase in potato tubers
Starch granule initiation is controlled by a heteromultimeric isoamylase in potato tubers
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DOI：
10.1073/pnas.0305920101
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发表时间：
2004-02-17
影响因子：
11.1
通讯作者：
Smith, AM
中科院分区：
文献类型：
--
作者：
Bustos, R;Fahy, B;Smith, AM
淀粉颗粒的起始还不清楚，但最近的证据表明，淀粉脱支酶，异淀粉酶，在控制这一过程。马铃薯块茎含有异淀粉酶活性，其可归因于含有Stisa 1和Stisa 2的异多聚体蛋白，Stisa 1和Stisa 2是马铃薯三种异淀粉酶基因中的两种的产物。为了发现这种酶是否参与淀粉粒起始，通过表达Stisa1或Stisa2的反义RNA来降低活性。转基因块茎积累了少量的可溶性葡聚糖，在结构上类似的植物糖原的谷物，拟南芥，和衣原体突变体缺乏异淀粉酶。然而，主要的影响是对淀粉粒的数量。转基因块茎积累了大量的微小颗粒没有看到在正常块茎。这些数据表明，异多聚体异淀粉酶在淀粉合成过程中起作用，以抑制质体基质中葡聚糖分子的起始，否则这些分子将结晶成核新的淀粉颗粒。
Starch granule initiation is not understood, but recent evidence implicates a starch debranching enzyme, isoamylase, in the control of this process. Potato tubers contain isoamylase activity attributable to a heteromultimeric protein containing Stisa1 and Stisa2, the products of two of the three isoamylase genes of potato. To discover whether this enzyme is involved in starch granule initiation, activity was reduced by expression of antisense RNA for Stisa1 or Stisa2. Transgenic tubers accumulated a small amount of a soluble glucan, similar in structure to the phytoglycogen of cereal, Arabidopsis, and Chlamydomonas mutants lacking isoamylase. The major effect, however, was on the number of starch granules. Transgenic tubers accumulated large numbers of tiny granules not seen in normal tubers. These data indicate that the heteromultimeric isoamylase functions during starch synthesis to suppress the initiation of glucan molecules in the plastid stroma that would otherwise crystallize to nucleate new starch granules.