A plant-specific protein, COST1, mediates autophagy to promote drought tolerance (PNAS)

Much remains to be learned about the sensing and signaling mechanisms controlling growth in response to drought. To dissect how plants control drought via autophagy, Bao et al. found a plant-specific protein, COST1 (CONSTITUTIVELY STRESSED 1) containing a DUF641 (domain of unknown function 641) domain, that is required for normal growth but negatively regulates drought response. Under normal growth conditions, the cost1 mutant grows much smaller than the wild type but with more drought resistance. The COST1 transcript does not change during stress treatments but the protein stability is affected by 26S-proteosome degradation pathway and autophagy. The subcellular localization of COST1 is observed as punctate-like structure in the cytoplasm upon drought treatment. COST1 also colocalizes and interacts with the autophagosome marker ATG8 (autophagy-related). The double mutants cost1 atg has similar drought-sensitive phenotype as the atg mutant, revealing the genetic interaction of ATG as a downstream component of COST1. This finding shows a plant-specific protein, COST1, regulates the balance between growth and drought resistance through autophagy. As COST1 is conserved throughout the plant kingdom, that will be interesting to study this gene as a potential drought tolerance protein in agricultural species. (Summary by Min May Wong) PNAS 10.1073/pnas.1918539117