The genetic mechanisms for multiseriate filament formation in cyanobacteria

本项目旨在确定蓝藻形态复杂性的遗传机制，并研究其进化历史。蓝细菌是一类具有光合作用的单系原核生物，具有漫长的进化轨迹。当代蓝藻是地球上大多数环境中的成功居民，并具有不同的基因型和表型特征。它们的形态多样性包括单细胞形式，通过二分裂分裂成在一个以上平面分裂的多细胞细丝，从而产生多列细丝和真正的分支。这种多样性使蓝藻成为最复杂的原核生物之一。蓝藻的共同祖先最有可能是单细胞的，而多细胞和真正的分支物种出现在进化后期。蓝细菌已被广泛研究，重点是光合作用和固氮生物学。然而，涉及多列和真正的分支形态的机制仍然是未知的，主要是因为形态复杂的蓝藻很少探索。在这里，我们使用multiseriate和真正的分支蓝藻作为模式生物，以解开这些表型的遗传机制。随着基因组序列在手，我们现在希望继续我们的目标，使用功能的方法，旨在确定参与多序列和真分支的形成和它们的关系与细胞骨架和细胞分裂机制的组成部分的蛋白质。整个门的比较基因组学有望揭示这些机制在进化过程中的出现。

This proposed project aims to identify the genetic mechanisms that are involved in cyanobacterial morphological complexity and to study their evolutionary history. Cyanobacteria are a monophyletic group of photosynthetic prokaryotes with a long evolutionary trajectory. Contemporary cyanobacteria are successful inhabitants in most environments on Earth and harbor diverse genotypic and phenotypic characteristics. Their morphological diversification comprise unicellular forms dividing by binary fission to multicellular filaments that divide in more than one plane, thus generating multiseriate filaments and true branches. This diversity places cyanobacteria among the most complex prokaryotes. The cyanobacterial common ancestor was most probably unicellular whereas multicellular and true branching species appeared later during evolution. Cyanobacteria have been extensively studied with a focus on the biology of photosynthesis and of nitrogen fixation. Yet the mechanisms involved in multiseriate and true-branching morphology are still unknown, mostly because morphologically complex cyanobacteria have been seldom explored. Here we use multiseriate and true-branching cyanobacteria as model organisms in order to unravel the genetic mechanisms underlying these phenotypes. With the genome sequences at hand, we now wish to proceed with our objective using a functional approach that is aimed to identify the proteins involved in multiseriate and true-branch formation and their relationship with components of the cytoskeleton and cell division machinery. Comparative genomics of the whole phylum is expected to shed light on the emergence of these mechanisms during evolution.