Identification of green lineage osmotic stress pathways

Abstract

Maintenance of water homeostasis is a fundamental cellular process required by all living organisms. Here, we use the green alga Chlamydomonas reinhardtii to establish a foundational understanding of evolutionarily conserved osmotic-stress signaling pathways in the green lineage through transcriptomics, phosphoproteomics, and functional genomics approaches. Five genes acting across diverse cellular pathways were found to be essential for osmotic-stress tolerance in Chlamydomonas including cytoskeletal organization, potassium transport, vesicle trafficking, mitogen-activated protein kinase and chloroplast signaling. We show that homologs of these genes in the multicellular land plant Arabidopsis thaliana have conserved functional roles in stress tolerance and reveal a novel PROFILIN-dependent actin remodeling stage of acclimation that ensures cell survival and tissue integrity upon osmotic stress. This study highlights the conservation of the stress response in algae and land plants and establishes Chlamydomonas as a unicellular plant model system to dissect the osmotic stress signaling pathway.

Cell wall integrity regulation across plant species

“…The connection between the extracellular signal and vacuolar expansion has not been fully elucidated, but the current hypothesis suggests that actin dynamics, which are regulated by the FER-interacting RAC/ROP GTPases, could be modulating vacuole size. Actin dynamics have been recently shown to respond to osmotic stress (NaCl and mannitol) by changing the orientation of their filaments by 90 degrees in Arabidopsis and Chlamydomonas (Vilarrasa-Blasi et al 2021 ). The FER-LRX-RALF module regulates the activity of salicylic acid (SA), JA, ABA and ROS pathways during plant growth under abiotic stress (Zhao et al 2021 ).…”