Jaiswal Priya, Qasim Falah, Mahto Arunima, Vichitra Ankur, Das Upasana, Tyagi Akhilesh K, Agarwal Pinky
National Institute of Plant Genome Research, New Delhi, India.
Interdisciplinary Centre for Plant Genomics and Department of Plant Molecular Biology, University of Delhi South Campus, New Delhi, India.
Physiol Plant. 2025 Jul-Aug;177(4):e70376. doi: 10.1111/ppl.70376.
Grain size is one of the key determinants of grain yield. Our study focuses on a novel seed-preferential CH zinc finger transcription factor, ZOS5-09 (LOC_Os05g38600) that plays an important role in regulating rice grain traits. Rice plants with the ZOS5-09 promoter::GUS construct showed high expression of ZOS5-09 in rice endosperm. In planta reporter effector assays and localization studies showed that ZOS5-09 is a nuclear-localized transcriptional repressor. It has two CH zinc finger domains and a C-terminal NoRS (nucleolar retention signal). Ectopic and seed-preferential overexpression of ZOS5-09 resulted in lethality. Seed-preferential overexpression without NoRS was detrimental to grain filling. Rice plants with knock-down or CRISPR-based knock-out of ZOS5-09 displayed reduced grain length and weight but increased grain width. Grain size change was due to lower cell proliferation and increased cell size in the transverse direction because of downregulation of cell cycle-related genes and increased expression of expansins. Decreased expression of ZOS5-09 also resulted in reduced total starch and protein content and higher endosperm chalkiness, thus negatively affecting grain quality. ZOS5-09 directly bound to a zinc finger-binding site and regulated a seed storage protein-encoding gene, GLU6. It acted as a repressor by promoting deacetylation upon interaction with a histone deacetylase. In summary, our results indicate that an optimum expression of ZOS5-09 is essential for proper rice grain development. Our study highlights the role of a transcriptional repressor in regulating rice grain traits and improves our understanding of the transcriptional regulatory networks affecting grain size.
粒型是决定谷物产量的关键因素之一。我们的研究聚焦于一种新型的种子优先表达的CH锌指转录因子ZOS5-09（LOC_Os05g38600），它在调控水稻粒型性状中发挥着重要作用。带有ZOS5-09启动子::GUS构建体的水稻植株在水稻胚乳中显示出ZOS5-09的高表达。在植物体内报告基因效应分析和定位研究表明，ZOS5-09是一种定位于细胞核的转录抑制因子。它有两个CH锌指结构域和一个C端核仁保留信号（NoRS）。ZOS5-09的异位表达和种子优先过表达导致致死性。没有NoRS的种子优先过表达对籽粒灌浆有害。通过敲低或基于CRISPR的敲除ZOS5-09的水稻植株粒长和粒重降低，但粒宽增加。粒型变化是由于细胞周期相关基因下调和扩张蛋白表达增加，导致横向细胞增殖降低和细胞大小增加。ZOS5-09表达降低还导致总淀粉和蛋白质含量降低以及胚乳垩白度增加，从而对籽粒品质产生负面影响。ZOS5-09直接结合到一个锌指结合位点并调控一个种子贮藏蛋白编码基因GLU6。它与组蛋白脱乙酰酶相互作用时通过促进去乙酰化发挥抑制因子的作用。总之，我们的结果表明ZOS5-09的最佳表达对水稻籽粒正常发育至关重要。我们的研究突出了转录抑制因子在调控水稻粒型性状中的作用，并增进了我们对影响粒型的转录调控网络的理解。
