A Putative Phosphatase, LSF1, Is Required for Normal Starch Turnover in Arabidopsis Leaves
A Putative Phosphatase, LSF1, Is Required for Normal Starch Turnover in Arabidopsis Leaves
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DOI：
10.1104/pp.109.148981
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发表时间：
2010-02-01
期刊：
影响因子：
7.4
通讯作者：
Smith, Alison M.
中科院分区：
文献类型：
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作者：
Comparot-Moss, Sylviane;Koetting, Oliver;Smith, Alison M.
一种假定的磷酸酶LSF 1（LIKE SEX 4;以前的PTPKIS 2）在序列和结构上与淀粉-EXCESS 4（SEX 4）密切相关，该酶是在拟南芥（Arabidopsis thaliana）叶片的淀粉降解过程中从淀粉聚合物中去除磷酸基团所必需的酶。我们表明，LSF 1也需要淀粉降解：lsf 1突变体，如sex 4突变体，有更多的淀粉在他们的叶子比野生型植物在整个昼夜循环。LSF 1是叶绿体，位于淀粉颗粒的表面。LSF 1和Sex 4突变体在糖敏感基因的表达方面相对于野生型植物显示出相似的广泛变化。然而，虽然LSF 1和SEX 4可能都参与了淀粉降解的早期阶段，但我们发现LSF 1既不催化与SEX 4相同的反应，也不介导该途径中的连续步骤。证据包括单突变体中磷酸化葡聚糖的含量和代谢。sex 4突变体积累可溶性磷酸寡糖在野生型植物中检测不到，是缺乏淀粉颗粒脱磷酸化活性存在于野生型植物。lsf 1突变体不显示这些表型。lsf 1/sex 4双突变体的表型也不同于这两个单突变体在几个方面。我们讨论了LSF 1蛋白在淀粉降解中可能发挥的作用。
A putative phosphatase, LSF1 (for LIKE SEX4; previously PTPKIS2), is closely related in sequence and structure to STARCH-EXCESS4 (SEX4), an enzyme necessary for the removal of phosphate groups from starch polymers during starch degradation in Arabidopsis (Arabidopsis thaliana) leaves at night. We show that LSF1 is also required for starch degradation: lsf1 mutants, like sex4 mutants, have substantially more starch in their leaves than wild-type plants throughout the diurnal cycle. LSF1 is chloroplastic and is located on the surface of starch granules. lsf1 and sex4 mutants show similar, extensive changes relative to wild-type plants in the expression of sugar-sensitive genes. However, although LSF1 and SEX4 are probably both involved in the early stages of starch degradation, we show that LSF1 neither catalyzes the same reaction as SEX4 nor mediates a sequential step in the pathway. Evidence includes the contents and metabolism of phosphorylated glucans in the single mutants. The sex4 mutant accumulates soluble phospho-oligosaccharides undetectable in wild-type plants and is deficient in a starch granule-dephosphorylating activity present in wild-type plants. The lsf1 mutant displays neither of these phenotypes. The phenotype of the lsf1/sex4 double mutant also differs from that of both single mutants in several respects. We discuss the possible role of the LSF1 protein in starch degradation.