Autophagy is a highly conserved self-degradation process that involves the degradation and recycling of cellular components and organelles. Although the involvement of autophagy in metabolic changes during fruit ripening has been preliminarily demonstrated, the variations in autophagic flux and specific functional roles in tomato fruit ripening remain to be elucidated. In this study, we analyzed the variations in autophagic flux during tomato fruit ripening. The results revealed differential expression of the SlATG8 family members during tomato fruit ripening. Transmission electron microscopy observations and dansylcadaverine (MDC) staining confirmed the presence of autophagy at the cellular level in tomato fruits. Furthermore, the overexpression of SlATG8f induced the formation of autophagosomes, increased autophagic flux within tomato fruits, and effectively enhanced the expression of ATG8 proteins during the color-transition phase of fruit ripening, thus promoting tomato fruit maturation. SlATG8f overexpression also led to the accumulation of vitamin C (VC) and soluble solids while reducing acidity in the fruit. Collectively, our findings highlight the pivotal role of SlATG8f in enhancing tomato fruit ripening, providing insights into the mechanistic involvement of autophagy in this process. This research contributes to a better understanding of the key factors that regulate tomato fruit quality and offers a theoretical basis for tomato variety improvement.

Autophagy is a mechanism for the degradation of cellular components in eukaryotes and plays a critical role in plant responses to abiotic stress. As a core member of the autophagy process, ATG8’s role in how plants respond to heat stress remains unclear. To investigate the response of the tomato autophagy core member ATG8f to heat stress, we studied the key gene ATG8f and generated tomato lines overexpressing SlATG8f using the recombinant expression vector pBWA(V)HS. We observed that under heat stress, SlATG8f overexpression (OE) plants exhibited decreased heat tolerance compared to wild-type (WT) plants. Specifically, OE plants showed increased relative electrolyte leakage, reduced soluble solid content, elevated chlorophyll content, and higher autophagosome numbers, with less damage to chloroplasts and mitochondria. Additionally, expression of some ATG8 family genes and heat shock protein-related genes was upregulated. Moreover, SlATG8f overexpressing plants had higher pollen vitality and more intact pollen morphology. These results suggest that while SlATG8f overexpression renders plants more sensitive to heat, it helps mitigate high-temperature damage to tomato pollen by maintaining chloroplast integrity and interacting with heat shock proteins to respond to heat stress.

Anther development in plants involves the precise regulation of numerous genes. This study delves into the role of endogenous melatonin in tomato anther development, utilizing tomato plants with a knockout of the key melatonin biosynthesis gene SlCOMT1 (slcomt1). The research revealed that SlCOMT1 is highly expressed in the anthers, and slcomt1 plants exhibited significantly reduced pollen viability and germination compared to WT plants, with reductions of approximately 34.7% and 34.3%, respectively. Notably, pollen from slcomt1 plants displayed anomalies, including partial deformities and adhesion. In addition, the germination status of slcomt1 seeds on the fifth day was lower compared to that of WT plants, and the expression of pollen development-related genes in slcomt1 plants was significantly inhibited to varying degrees. This study underscores the pivotal role of endogenous melatonin in tomato anther development, paving the way for deeper investigations into the biological function of SlCOMT1. These findings hold great promise for shedding light on further research and applications of melatonin in the agricultural field.