Autophagy involvement in responses to abscisic acid by plant cells.

Plants are sessile organisms and therefore are affected by different environmental stresses, including salinity, drought, high light, high temperature or freezing (generically referred to as abiotic stresses). These conditions can be perceived, in part, as a transient or permanent water deficit and result in the accumulation of the stress phytohormone abscisic acid (ABA), which regulates the expression of ABA-responsive genes. Some of these ABA-induced proteins are only transiently required, and therefore the plant cell needs an efficient regulatory mechanism for transcriptionally and/or post-translationally regulating their expression/degradation. Although many transcriptional regulatory mechanisms have been characterized, the question of how, when and where transiently ABA-induced proteins are targeted for degradation has not been addressed. A case study with the Arabidopsis thaliana tryptophan-rich sensory protein-related (At-TSPO), a membrane protein transiently induced by abiotic stress, revealed a complex interaction between heme metabolism and selective autophagy resulting in downregulation of At-TSPO.