Initiation of B-type starch granules in wheat endosperm requires the plastidial a-glucan phosphorylase PHS1
Initiation of B-type starch granules in wheat endosperm requires the plastidial a-glucan phosphorylase PHS1
复制标题
小麦胚乳中 B 型淀粉颗粒的启动需要质体 a-葡聚糖磷酸化酶 PHS1
DOI：
10.1101/2023.06.01.543270
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Kamble N
中科院分区：
文献类型：
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作者：
Kamble N
胞质α-葡聚糖磷酸化酶(PHS1)可以延长和降解麦芽低聚糖(MOSS)，但其在植物中的确切生理作用尚不清楚。在这里，我们发现了PHS1在建立小麦(Triticumspp.)淀粉粒独特的双峰特性中的特殊作用。胚乳。小麦胚乳含有在籽粒发育早期形成的大的A型颗粒和在籽粒发育后期形成的小的B型颗粒。我们证明了PHS1与B颗粒CONTENT1(BGC1)相互作用，BGC1是正常B型颗粒启动所必需的碳水化合物结合蛋白。PHS1同源基因缺失的四倍体硬粒小麦突变体具有正常的A型颗粒，但B型颗粒较少且较大。突变对籽粒大小和淀粉含量没有影响。此外，通过评估phs1突变体在籽粒发育过程中的颗粒数量以及利用PHS1和BGC1中的双突变缺陷，我们证明PHS1仅参与B型颗粒的启动。PHS1基因在小麦叶片中的总淀粉含量和每个叶绿体的淀粉粒数不受PHS1基因缺失的影响，表明PHS1基因在小麦籽粒形成中的作用仅限于胚乳。因此，我们认为A型和B型颗粒的启动是通过不同的生化机制进行的，其中PHS1在B型颗粒的启动中起着唯一的作用。
The plastidial α-glucan phosphorylase (PHS1) can elongate and degrade maltooligosaccharides (MOSs), but its exact physiological role in plants is poorly understood. Here, we discover a specialized role of PHS1 in establishing the unique bimodal characteristic of starch granules in wheat (Triticumspp.) endosperm. Wheat endosperm contains large A-type granules that initiate at early grain development and small B-type granules that initiate in later grain development. We demonstrate that PHS1 interacts with B-GRANULE CONTENT1 (BGC1), a carbohydrate-binding protein essential for normal B-type granule initiation. Mutants of tetraploid durum wheat (Triticum turgidum) deficient in all homoeologs of PHS1 had normal A-type granules but fewer and larger B-type granules. Grain size and starch content were not affected by the mutations. Further, by assessing granule numbers during grain development in thephs1mutant and using a double mutant defective in both PHS1 and BGC1, we demonstrate that PHS1 is exclusively involved in B-type granule initiation. The total starch content and number of starch granules per chloroplast in leaves were not affected by loss of PHS1, suggesting that its role in granule initiation in wheat is limited to the endosperm. We therefore propose that the initiation of A- and B-type granules occurs via distinct biochemical mechanisms, where PHS1 plays an exclusive role in B-type granule initiation.