Jia Shangang, Yobi Abou, Naldrett Michael J, Alvarez Sophie, Angelovici Ruthie, Zhang Chi, Holding David R
College of Grassland Science and Technology, China Agricultural University, Beijing, China.
Key Laboratory of Pratacultural Science, Beijing Municipality, Beijing, China.
J Exp Bot. 2020 Oct 7;71(19):5880-5895. doi: 10.1093/jxb/eraa325.
Opaque kernels in maize may result from mutations in many genes, such as OPAQUE-2. In this study, a maize null mutant of RNA-DIRECTED DNA METHYLATION 4 (RDM4) showed an opaque kernel phenotype, as well as plant developmental delay, male sterility, and altered response to cold stress. We found that in opaque kernels, all zein proteins were reduced and amino acid content was changed, including increased lysine. Transcriptomic and proteomic analysis confirmed the zein reduction and proteomic rebalancing of non-zein proteins, which was quantitatively and qualitatively different from opaque-2. Global transcriptional changes were found in endosperm and leaf, including many transcription factors and tissue-specific expressed genes. Furthermore, of the more than 8000 significantly differentially expressed genes in wild type in response to cold, a significant proportion (25.9% in moderate cold stress and 40.8% in near freezing stress) were not differentially expressed in response to cold in rdm4, suggesting RDM4 may participate in regulation of abiotic stress tolerance. This initial characterization of maize RDM4 provides a basis for further investigating its function in endosperm and leaf, and as a regulator of normal and stress-responsive development.
玉米中的不透明籽粒可能由许多基因的突变导致，例如不透明2基因（OPAQUE-2）。在本研究中，一个RNA介导的DNA甲基化4（RDM4）的玉米缺失突变体表现出不透明籽粒表型，以及植株发育延迟、雄性不育和对冷胁迫反应的改变。我们发现，在不透明籽粒中，所有醇溶蛋白都减少，氨基酸含量发生变化，包括赖氨酸增加。转录组学和蛋白质组学分析证实了醇溶蛋白的减少以及非醇溶蛋白的蛋白质组重新平衡，这在数量和质量上与不透明2突变体不同。在内胚乳和叶片中发现了全局转录变化，包括许多转录因子和组织特异性表达基因。此外，在野生型中超过8000个对冷胁迫有显著差异表达的基因中，很大一部分（中度冷胁迫下为25.9%，接近冰冻胁迫下为40.8%）在rdm4中对冷胁迫没有差异表达，这表明RDM4可能参与非生物胁迫耐受性的调控。玉米RDM4的这一初步特征为进一步研究其在内胚乳和叶片中的功能以及作为正常和胁迫响应发育的调节因子提供了基础。
