Overexpression of SlATG8f gene enhanced autophagy and pollen protection in tomato under heat stress

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.