STARCH SYNTHASE 4 is required for normal starch granule initiation in amyloplasts of wheat endosperm
STARCH SYNTHASE 4 is required for normal starch granule initiation in amyloplasts of wheat endosperm
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DOI：
10.1101/2021.01.29.428798
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发表时间：
2021-01
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影响因子：
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通讯作者：
Erica Hawkins;Jiawen Chen;Alexander Watson‐Lazowski;J. Ahn-Jarvis;J. Barclay;B. Fahy;Matthew Hartley-Matthew
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作者：
Erica Hawkins;Jiawen Chen;Alexander Watson‐Lazowski;J. Ahn-Jarvis;J. Barclay;B. Fahy;Matthew Hartley-Matthew
在分子水平上对淀粉颗粒的形成知之甚少。葡萄糖基转移酶淀粉合成酶4 （SS4）在拟南芥叶片的颗粒形成中起核心作用，但其在谷物胚乳中的功能尚不清楚。我们研究了SS4在小麦中的作用，小麦在籽粒发育过程中具有明显的颗粒形成时空模式。我们在四倍体小麦（Triticum turgidum）中产生了两个SS4同源性缺陷的TILLING突变体。研究了胚乳淀粉在发育和成熟籽粒中的形态。SS4缺乏导致胚乳淀粉颗粒形态发生严重改变。在籽粒发育早期，野生型在每个淀粉体中形成单个“a型”颗粒，而突变体中大多数淀粉体由于多次形成而形成复合颗粒。这种表型类似于缺乏b -颗粒CONTENT 1 （BGC1）的突变体。缺乏SS4也降低了叶片和花粉粒的淀粉含量。我们认为，SS4和BGC1是在籽粒发育早期适当控制颗粒形成所需的，从而导致每个淀粉质体形成单个a型颗粒。任何一种蛋白的缺失都会导致每个淀粉体起始数量的变化和复合颗粒的形成。
Starch granule initiation is poorly understood at the molecular level. The glucosyltransferase, STARCH SYNTHASE 4 (SS4), plays a central role in granule initiation in Arabidopsis leaves, but its function in cereal endosperms is unknown. We investigated the role of SS4 in wheat, which has a distinct spatiotemporal pattern of granule initiation during grain development. We generated TILLING mutants in tetraploid wheat (Triticum turgidum) that are defective in both SS4 homoeologs. The morphology of endosperm starch was examined in developing and mature grains. SS4 deficiency led to severe alterations in endosperm starch granule morphology. During early grain development, while the wild type initiated single ‘A-type’ granules per amyloplast, most amyloplasts in the mutant formed compound granules due to multiple initiations. This phenotype was similar to mutants deficient in B-GRANULE CONTENT 1 (BGC1). SS4 deficiency also reduced starch content in leaves and pollen grains. We propose that SS4 and BGC1 are required for the proper control of granule initiation during early grain development that leads to a single A-type granule per amyloplast. The absence of either protein results in a variable number of initiations per amyloplast and compound granule formation.