Nuclear body structures in transcriptional regulation of seed size control and/or plant defence pathways.

随着世界人口的增加和气候变化对耕地的负面影响，确保未来的粮食安全将变得越来越重要。大米养活了世界上一半的人口，人们做出了巨大的努力，通过育种来提高产量。许多遗传证据表明，MAPK(丝裂原活化蛋白激酶)级联促进了更大颗粒的发育，但下游的分子机制仍不清楚。我们确定IKU1(已知的在拟南芥中转录调节种子/胚乳发育的复合体的一个成分)是MAPK的磷酸化底物。因此，在与印度同事的合作中，我们建议测试这一假设，即候选水稻Iku样蛋白是否可能是MAPK级联下游颗粒大小控制的缺失环节。同时，我们将利用拟南芥系统对支持IKU1功能的分子机制进行功能阐明。与预测的固有无序和PrD样区一致，我们观察到当与GFP-Tag融合时，IKU1定位于核焦点。初步结果提示，MAPK在病灶动力学中起着重要的作用。这种焦点可能代表蛋白质分成生物分子凝聚体或有时被称为“无膜细胞器”，这是一个新兴的研究领域。生物分子凝聚物被认为有助于促进局部高蛋白质浓度来驱动某些生化过程。在这个应用中，我们建议研究IKU1中的蛋白质形式(翻译后修饰、剪接变体、类PRD促进氨基酸的自然变异)如何影响凝聚动力学和/或它与蛋白质伙伴的相互作用-目的是将这些数据与种子大小控制或最终与植物防御调控的串扰联系起来。

Ensuring food security in the future will be of increasing importance with the rising world population and negative impact from climate change on arable land. Rice feeds half the world’s population and there has been tremendous efforts to increase yield through breeding. Many lines of genetic evidence point to a MAPK (mitogen-activated protein kinase) cascade that promote larger grain size development but the downstream molecular mechanism is still unknown. We identified IKU1 (a component of a complex known to transcriptionally regulate seed/endosperm development in Arabidopsis) to be a MAPK phospho-substrate. Therefore, in collaboration with colleagues in India, we propose to test the hypothesis if a candidate rice IKU-like protein might be the missing link to grain size control downstream of the MAPK cascade. In parallel, we will utilize the Arabidopsis system for functional elucidation of the molecular mechanism underpinning IKU1 functions. In agreement to predicted intrinsic disorder and prion domain-like (PrD-like) regions, we observed IKU1 localization to nuclear foci when fused to a GFP-tag. Preliminary results suggest a MAPK-mediated effect on foci dynamics. Such foci presumably represent phase partitioning of proteins into biomolecular condensates or sometimes referred to as “membrane-less organelles”, which is an emerging field of research. Biomolecular condensates are thought to facilitate high local protein concentrations to drive certain biochemical processes. In this application, we propose to study how proteoforms (post-translational modifications, splice variants, natural variations in PrD-like promoting amino acids) in IKU1 affect the condensate dynamics and/or its interaction with protein partners – with the aim to link these data to seed size control or eventual crosstalk to plant defence regulation.