Chloroplast Recycling and Plant Stress Tolerance

Abstract

Plastids have emerged as pivotal regulators of plant’s response to biotic and abiotic stresses. Chloroplasts have the ability to synthesize a variety of pigments, secondary metabolites, and phytohormones which help plant cells to withstand adverse conditions. Further, plastids communicate with the nucleus and other cellular organelles for the acquisition of essential molecules to survive under unfavorable conditions. They act as environmental sensors which not only synthesize molecules for stress tolerance but also induce nucleus-encoded genes for stress resilience. Senescence is a key developmental process in this context and plays an important role in the release of essential nutrients. Chloroplast proteolytic machinery plays a crucial role in the degradation or remodeling of plastid proteins resulting in the generation of numerous endogenous peptides which are present in the plant secretome. Plastid chaperone system is also activated for the repair/refold of damaged proteins resulting in improved tolerance to stresses. Autophagy is a conserved process that involves large-scale breakdown of chloroplast through piecemeal degradation and chlorophagy. The piecemeal degradation occurs through Rubisco-containing bodies (RCBs) and senescence-associated vacuoles (SAVs), whereas chlorophagy targets chloroplasts as a whole. Though information about chloroplast recycling is limited, the present work provides a comprehensive review on chloroplast recycling and its role in stress mitigation and adaptation in climate change scenarios.