COST1 balances plant growth and stress tolerance via attenuation of autophagy.

In plants, macroautophagy/autophagy has been reported to function in various biotic and abiotic stress-response pathways, but few direct regulators linking stress and autophagy have yet been identified. Other than the conserved nutrient sensing kinase TOR (Target of Rapamycin), negative regulators that can directly modulate plant autophagy are unknown. We recently identified a mutant, termed cost1 (Constitutively Stressed 1), which has strong drought tolerance with constitutive induction of autophagy and broad expression of normally stress-responsive genes. The COST1 protein negatively regulates autophagy by direct interaction with the key autophagy adaptor ATG8E, thus directly linking autophagy and drought tolerance. Moreover, plant growth and development in a cost1 mutant is greatly retarded, suggesting that COST1 controls the tradeoff between growth and stress tolerance.