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

随着世界人口的不断增加和气候变化对可耕地的负面影响，确保未来的粮食安全将变得越来越重要。水稻养活了世界上一半的人口，人们已经做出了巨大的努力来通过育种提高产量。许多遗传学证据表明，MAPK（丝裂原活化蛋白激酶）级联反应促进了更大的晶粒尺寸的发展，但下游的分子机制仍然未知。我们确定IKU 1（一种已知在拟南芥中转录调节种子/胚乳发育的复合物的组分）是MAPK磷酸化底物。因此，在与印度的同事合作，我们建议测试的假设，如果一个候选水稻IKU样蛋白可能是缺失的环节，以控制下游的MAPK级联的晶粒大小。与此同时，我们将利用拟南芥系统的IKU 1功能的分子机制的功能阐明。与预测的内在疾病和朊病毒结构域样（PrD样）区域一致，我们观察到IKU 1与GFP标签融合时定位于核灶。初步结果表明，MAPK介导的影响焦点动态。这种病灶可能代表蛋白质相分配成生物分子凝聚物，有时也称为“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促进高局部蛋白质浓度以驱动某些生化过程。在本申请中，我们建议研究IKU 1中的蛋白形式（翻译后修饰，剪接变体，PrD样促进氨基酸的自然变异）如何影响冷凝物动力学和/或其与蛋白质伴侣的相互作用-目的是将这些数据与种子大小控制或最终串扰植物防御调控联系起来。

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.