Draparnaldia – a model alga for studying terrestrialisation in Chlorophytes

• Applicant: Lenka Caisova, Ph.D.
• Subject Area: Plant Genetics and Genomics
• Term: from 2017 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 372316352

The colonization of land by green plants was one of the most significant events in Earth history. This event necessitated a suite of plant adaptations necessary for their survival and subsequent radiation in terrestrial environments. It is generally accepted that land plants emerged from the streptophytes, their last common ancestor being a freshwater charophyte alga. But it is also well known that many chlorophytes possess a broad range of adaptations to (semi)terrestrial habitats, and a morphological similarity with the protonemal stages of mosses. This raises an important question of why land plants originated from the streptophyte and not from the chlorophyte lineage? The first step towards understanding why chlorophytes did not radiate on land is to understand their terrestrialisation. Therefore, in this project, I aim to focus on the molecular responses to desiccation – a key feature of the transition of plants to the terrestrial environment. I will compare the molecular mechanisms of desiccation tolerance exhibited by two plants (Draparnaldia - chlorophyte and the model moss Physcomitrella patens - streptophyte), with similar morphological characteristics and growth habits but separated by almost 1 billion years of evolution. I will perform: (i) transcriptomic analysis of Draparnaldia to identify adaptive genes associated with desiccation; (ii) functional analysis between Draparnaldia and Physcomitrella to determine the extent of functional conservation across 1 billion years of evolution; and (iii) initiate algal transformation to open the way to investigate mutant strains by complementation experiments (e.g. by CRISPR/Cas9-mediated genome editing) and estimation of the Draparnaldia genome size for future genome sequencing. The knowledge gained from this project will contribute to understanding two principal questions about the evolution of desiccation tolerance: (a) how similar/different are strategies adopted in chlorophytes and streptophytes, and (b) whether the adaptive genes functional in land plant terrestrialisation were present in ancestral form in the chlorophytes. Moreover, this project will be the first step towards developing a semi-terrestrial filamentous alga, Draparnaldia, as a model system to study cellular differentiation, development, and environmentally responsive growth in chlorophytes.

• DFG Programme: Research Fellowships
• International Connection: United Kingdom
• Host: Dr. Andrew C. Cuming