Evolutionary adaptations of the microtubule cytoskeleton during cell division in the land plant lineage

大约450万年前，祖先链藻对陆地栖息地的定植，以及随后陆地植物的兴起，依赖于新型微管细胞骨架阵列的进化，并伴随着植物特异性微管相关蛋白（MAPs）的多样化和出现，以调整细胞过程以适应新的条件和相互作用。植物细胞骨架组织的关键创新之一是前前期带(PPB)/片质体系统的出现。该系统促进了细胞分裂模式的转换，从基于切割的机制到由内到外的机制，在这种机制中，新的细胞壁插入到细胞中心。拟南芥的功能研究发现了控制PPB和片质体形成的真核和植物特异性map网络。然而，这些复合体的起源、结构和动力学仍然未知。植物特异性IQ67 DOMAIN （IQD）蛋白是拟南芥中PPB形成和分裂平面控制的关键调控因子，并被认为是微管相关PPI网络的枢纽。iqd具有类似支架的特性，与已知的植物细胞分裂调节因子相互作用，并涉及生长素依赖的分裂平面定位控制。我们的初步数据表明，在陆地植物进化的早期，iqd就出现了。我们假设植物特异性IQD支架促进了细胞骨架上PPIs的重新布线和获取，以支持植物细胞分裂和生长调节过程中的新功能化和功能特化。在这个项目中，我们的目标是通过研究iqd组装的PPI网络的进化及其在细胞分裂中的功能来确定控制微管细胞骨架适应性的关键原则。我们将通过对多形地菜（Marchantia polymorpha）中IQD功能的功能分析，以及对链藻、苔藓植物和种子植物中IQD的微管结合和PPI特异性的比较分析来实现这些目标。

The colonization of terrestrial habitats by ancestral streptophyte algae approximately 450 Mya ago, followed by the rise of land plants relied on the evolution of novel microtubule cytoskeletal arrays and was accompanied by the diversification and emergence of plant-specific microtubule-associated proteins (MAPs) to adjust cellular processes to novel conditions and interactions. One of the key innovations in plant cytoskeleton organization is the emergence of the preprophase band (PPB)/phragmoplast system. This system facilitates a switch in the mode of cell division from a cleavage-based mechanisms to an inside-out mechanism, in which new cell walls are inserted at the cell center. Functional studies in Arabidopsis thaliana identified networks of eukaryotic and plant-specific MAPs that control the formation of the PPB and phragmoplast. The origin, architecture and dynamics of these complexes, however, are still unknown. Plant-specific IQ67 DOMAIN (IQD) proteins emerged as key regulators of PPB formation and division plane control in Arabidopsis thaliana with proposed functions as hubs in microtubule-associated PPI networks. IQDs share scaffold-like properties, physically interact with known regulators of plant cell division, and are implicated in auxin-dependent control of division plane positioning. Our preliminary data indicate emergence of IQDs early during land plant evolution. We hypothesize that plant-specific IQD scaffolds facilitated the rewiring and acquisition of PPIs at the cytoskeleton to support neo-functionalization and functional specialization during plant cell division and growth regulation. In this project, we aim to identify key principles that govern the adaptations of the microtubule cytoskeleton by investigating the evolution of IQD-assembled PPI networks and their function in cell division. We will approach these aims by functional analyses of IQD functions in the liverwort Marchantia polymorpha and by comparative analyses of microtubule-binding and PPI specificities of IQDs from streptophyte algae, bryophytes, and seed plants.