The critical role of autophagy in plant responses to abiotic stresses

Autophagy is an evolutionary conserved recycling process in eukaryotes whereby intracellular components are engulfed by autophagosomes, which are subsequently transferred to the vacuoles for further degradation and reuse. In organisms like yeast and metazoans, autophagy is actively engaged during environmental perturbation either by degrading denatured proteins and organelles or by interfacing with stress related signaling molecules. Studies over the last decade have also revealed numerous important mechanisms where autophagy is widely involved in plant abiotic stress responses. Autophagy serves as a pivotal route for nutrient remobilization by the degradation of superfluous or damaged cellular cytoplasmic material and organelles. It is also reported to regulate the accumulation of reactive oxygen species, to maintain the cellular redox balance of plants under stressful conditions. Furthermore, autophagy is essential in regulating cellular toxicity by removing aggregated and/or denatured proteins and thereby improving plant stress tolerance. In this review, recent advances in our understanding of autophagy, along with pathways and regulatory networks through which it influences many aspects of plant growth and development in response to nutrient starvation, oxidative stress, osmotic stress and extreme temperatures are discussed.