Klebsome: Klebsormidiophyceaen genome diversity and adaptations to terrestrial environments

• Applicant: Professor Dr. Jan de Vries
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 509535047

Our planet is covered by land plants. All of this biodiversity evolved from algae in a singular event that set the conquest of land by plants in motion, forever changing the face of our planet. Major phylogenomic efforts have established a robust framework for understanding this singularity: The green lineage is deeply split into the chlorophytes and the streptophytes. The streptophytes encompass the land plants and the streptophyte algae. Among these streptophyte algae, the Zygnematophyceae followed by the Coleochaetophyceae were pinpointed as closest algal relatives to land plants. However, the arguably most resilient land colonizers among streptophyte algae are the Klebsormidiophyceae, which shared a common ancestor with land plants more than 700 million years ago. I hypothesize that, despite their phylogenetic distance, klebsormidiophyceaen resilience is built on a genetic chassis that is conserved between land plants and their algal relatives—across 700 million years of streptophyte evolution. Klebsormidium nitens was the first streptophyte alga to have its nuclear genome sequenced. It was found to bear a surprising number of land plant heritage genes—but at the time there were no other genomes of streptophyte algae to contextualize these results. Now, we have genome coverage of almost all major groups of streptophyte algae. Yet, Klebsormidium still stands out regarding the contiguity of pathways and signaling cascades classically ascribed to land plants—especially in light of its more than 700 million years divergence from land plants. The ubiquity of Klebsormidiophyceae in terrestrial environments is likely written in their genes—potentially those shared with land plants. In this project, we will build upon the experience my team and I have garnered in functional genomics on diverse streptophyte algae. We will test the hypothesis that a robust genetic backbone for response pathways to environmental factors, such as the phenylpropanoid biosynthesis genes, is shared by all Klebsormidiophyceae—and a potential synapomorphy of Klebsormidiophyceae and Phragmoplastophyta. We will: (1) establish a phylogenomic framework for Klebsormidiophyceae by performing the first systematic phylogenomic survey of the class Klebsormidiophyceae; (2) sequence four genomes of Klebsormidiophyceae to facilitate robust inference of trait evolution; (3) generate global gene expression data of diverse Klebsormidiophyceae challenged by terrestrial stressors to establish a fine-grained response profile that is common to all four Klebsormidiophyceae; (4) compare and redefine synapomorphies using the functional genomic data. By integrating the robust genomic backbone with gene expression profiles and analyses of important candidate gene families, we will define the stress responsive coding capacity salient to (a) the clade Klebsormidiophyceae and (b), contextualized with land plant data, reconstruct their common ancestor that existed more than 700 million years ago.

• DFG Programme: Research Grants