`Self-eating` before being eaten - Role of autophagy in fruit ripening

Fruit ripening and stress tolerance have significant implications on global food security, and their modulation may directly contribute to sustainable agriculture. The tomato fruit is a major crop that is also serving as a model system for fleshy fruit research. Fruit ripening involves major biochemical reprogramming, leading to tissue softening, color change, degradation of toxic compounds, volatile production, and soluble sugar assembly. Substantial remodeling of the fruit cellular content, including the proteome, is required to allow these changes, involving the fine-tuning of synthesis and degradation events at each ripening stage. One of the major cellular degradation pathways in eukaryotes is macroautophagy (hereafter referred to as autophagy). Autophagy involves generating a double-membrane structure, termed autophagosome, around the cytosolic cargo destined for degradation in the vacuole. ATG8 gene and protein (both lipidated and nonlipidated forms) expression analysis along with confocal live-imaging of mCherry-ATG8 confirmed the increased function of autophagy along ripening progression. Induction of autophagy using the TOR inhibitor AZD8055 and silencing of SlATG2 using virus-induced gene silencing (VIGS) showed that autophagy has an essential role to play in the process of tomato fruit ripening. Our research highlights a yet unfamiliar role of autophagy in fruit development and may allow the development of autophagy-based methods to reduce food loss and prolong fruit shelf life.