Maize Miniature Seed6 Encoding an Endoplasmic Reticulum Signal Peptidase is Critical in Seed Development
Maize Miniature Seed6 Encoding an Endoplasmic Reticulum Signal Peptidase is Critical in Seed Development
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编码内质网信号肽酶的玉米微型种子6对于种子发育至关重要
DOI：
10.1093/plphys/kiaa060
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发表时间：
--
期刊：
影响因子：
7.4
通讯作者：
Song Weibin
中科院分区：
文献类型：
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作者：
Yi Fei;Song Weibin
内质网(ER)I型信号肽酶(ER SPase I)是从分泌的蛋白质中裂解信号肽的重要酶。然而，ER Spase I在植物中的具体功能还没有遗传特征，底物也很大程度上是未知的。在这里，我们报告了一个玉米(Zea Mays)微型种子6(Mn6)突变体的鉴定。功能缺失突变体mn6的胚乳大小显著减小。基于图谱的克隆和分子鉴定表明，Mn6是一个S26家族ER Spase I，Mn6中的Gly102(E框)在加工过程中对蛋白质功能起关键作用。质谱学和免疫沉淀分析表明，Mn6主要参与处理与碳水化合物合成相关的蛋白质，包括在胚乳底层转运层特异表达的细胞壁转化酶微型种子1(Mn1)。突变体中Mn1的RNA和蛋白质表达水平均显著下调。由于转移细胞层的细胞壁转化酶活性显著降低，Mn6突变导致胚乳发育严重缺陷。这些结果表明，Mn6对Mn1的适当成熟可能是种子适当灌浆和玉米发育的关键步骤。
Endoplasmic reticulum (ER) type I signal peptidases (ER SPases I) are vital proteases that cleave signal peptides from secreted proteins. However, the specific function of ER SPase I in plants has not been genetically characterized, and the substrate is largely unknown. Here, we report the identification of a maize (Zea mays)miniature seed6(mn6) mutant. The loss-of-functionmn6mutant exhibited severely reduced endosperm size. Map-based cloning and molecular characterization indicated that Mn6 is an S26-family ER SPase I, with Gly102 (box E) in Mn6 critical for protein function during processing. Mass spectrometric and immunoprecipitation analyses revealed that Mn6 is predominantly involved in processing carbohydrate synthesis-related proteins, including the cell wall invertase miniature seed1 (Mn1), which is specifically expressed in the basal endosperm transfer layer. RNA and protein expression levels of Mn1 were both significantly downregulated in themn6mutant. Due to the significant reduction in cell wall invertase activity in the transfer cell layer, mutation ofMn6caused dramatic defects in endosperm development. These results suggest that proper maturation of Mn1 by Mn6 may be a crucial step for proper seed filling and maize development.