• Protein bodies (PBs), the major protein storage organelle in maize (Zea mays) endosperm, comprise zeins and numerous nonzein proteins (NZPs). Unlike zeins, how NZPs accumulate in PBs remains unclear.
• We characterized a maize miniature kernel mutant, mn*, that produces small kernels and is embryo-lethal. After cloning the Mn* locus, we determined that it encodes the mitochondrial 50S ribosomal protein L10 (mRPL10). MN* localized to mitochondria and PBs as an NZP; therefore, we renamed MN* Non-zein Protein 1 (NZP1). Like other mutations affecting mitochondrial proteins, mn* impaired mitochondrial function and morphology.
• To investigate its accumulation mechanism to PBs, we performed protein interaction assays between major zein proteins and NZP1, and found that NZP1 interacts with 22 kDa α-zein. Levels of NZP1 and 22 kDa α-zein in various opaque mutants were correlated. Furthermore, NZP1 accumulation in induced PBs depended on its interaction with 22 kDa α-zein. Comparative proteomic analysis of PBs between wild-type and opaque2 revealed additional NZPs. A new NZP with plastidial localization was also found to accumulate in induced PBs via interaction with 22 kDa α-zein.
• This study thus reveals a mechanism for accumulation of NZPs in PBs and suggests a potential application for the accumulation of foreign proteins in maize PBs.

中文翻译：

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22 kDa α-玉米醇溶蛋白介导的非玉米醇溶蛋白在玉米胚乳蛋白体中的积累

• 蛋白质体 (PBs) 是玉米 ( Zea mays ) 胚乳中主要的蛋白质储存细胞器，包含玉米醇溶蛋白和许多非玉米醇溶蛋白 (NZP)。与玉米蛋白不同，NZPs 如何在 PBs 中积累仍不清楚。
• 我们表征了玉米微型内核突变体mn *，它产生小内核并且是胚胎致死的。克隆Mn * 基因座后，我们确定它编码线粒体 50S 核糖体蛋白 L10 (mRPL10)。MN* 作为 NZP 定位于线粒体和 PBs；因此，我们将 MN* 非玉米醇溶蛋白 1 (NZP1) 重新命名。与其他影响线粒体蛋白的突变一样，mn * 会损害线粒体功能和形态。
• 为了研究其对 PBs 的积累机制，我们进行了主要玉米醇溶蛋白和 NZP1 之间的蛋白质相互作用测定，发现 NZP1 与 22 kDa α-玉米醇溶蛋白相互作用。各种不透明突变体中NZP1 和 22 kDa α-玉米醇溶蛋白的水平是相关的。此外，诱导的 PBs 中 NZP1 的积累取决于其与 22 kDa α-玉米醇溶蛋白的相互作用。野生型和不透明 2之间PBs 的比较蛋白质组学分析揭示了额外的 NZPs。还发现具有质体定位的新 NZP 通过与 22 kDa α-玉米醇溶蛋白的相互作用在诱导的 PB 中积累。
• 因此，该研究揭示了 NZP 在 PBs 中积累的机制，并提出了在玉米 PBs 中积累外源蛋白的潜在应用。