ProMAlgate: A protein chassis definition of multicellularity in the closest Algal relatives of land plants

• Applicant: Professor Dr. Jan de Vries
• Subject Area: Evolution and Systematics of Plants and Fungi
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 569599232

One fascinating topic in evolutionary biology is the multiple independently transition from unicellularity to multicellularity, leading to the rise of key groups like embryophytes (land plants), which are the only organisms to have conquered terrestrial habitats on a global scale. Surprisingly, the closest algal relatives of land plants are the Zygnematophyceae, a group with relatively simple unicellular or filamentous body plans. Research from my lab indicates that the repeated shifts from unicellularity to multicellularity rely on an ancient genetic framework. Recently, we updated the genomic resources for unicellular and multicellular zygnematophytes. Now we can explore the differences between unicellular and multicellular forms of the closest algal relatives of land plants. Preliminary data show that we can (a) alter the cell shape of unicells—while multicellular forms remain more stable—using environmental stimuli and (b) collect time-course RNAseq and proteomic data. This enables us to manipulate cell division and study the morphogenetic effects of environmental triggers. Our work aims to test the hypothesis that both unicellular and filamentous zygnematophytes share a toolkit for multicellular morphogenesis, which facilitates the realization of multicellularity through dynamic deployment and functions similarly in land plants. We found that cell division genes crucial to embryophyte traits like phragmoplast formation co-express even in unicellular zygnematophytes. We will test if their role in multicellular growth and morphogenesis depends on time-course dynamic deployment. We will use the MAdLand systems Mesotaenium endlicherianum, Zygnema circumcarinatum, and Physcomitrium patens as land plant references to pursue three synergistic but independent objectives: 1. Generate a time-course framework for cell division in the closest algal relatives of land plants. Our previous work demonstrated that co-expression data could identify functional modules of cell division genes even in random populations of zygnematophyte cells, and here, we will track this across the three species throughout their diurnal cycle. 2. Identify key morphogenetic cell division proteins in unicellular and multicellular zygnematophytes through manipulation. We have observed that environmental cues can change cell shape in zygnematophytes, which allows us to study proteins involved in morphogenic cell division and understand the feedback on the cell division framework. 3. Probe the conservation of cell division factors. We have identified the phragmoplast orienting kinase as a key hub in zygnematophyte cell division gene networks. By cross-species complementation in double KO pok1 pok2 Arabidopsis lines, we aim to elucidate its role. Additionally, using antibodies against cytoskeletal components and methods for isolating the cytoskeleton, we will attempt to pull down parts of the division machinery during the cell cycle.

• DFG Programme: Research Grants