Interactions between 2-Cys peroxiredoxins and ascorbate in autophagosome formation during the heat stress response in Solanum lycopersicum

2-Cys peroxiredoxins (2-CPs) function in the removal of hydrogen peroxide and lipid peroxides but their precise roles in the induction of autophagy have not been characterized. Here we show that heat stress, which is known to induce oxidative stress, leads to the simultaneous accumulation of transcripts encoding 2-CPs and autophagy proteins, as well as autophagosomes, in tomato (Solanum lycopersicum) plants. Virus-induced gene silencing of the tomato peroxiredoxin genes 2-CP1, 2-CP2, and 2-CP1/2 resulted in an increased sensitivity of tomato plants to heat stress. Silencing 2-CP2 or 2-CP1/2 increased the levels of transcripts associated with ascorbate biosynthesis but had no effect on the glutathione pool in the absence of stress. However, the heat-induced accumulation of transcripts associated with the water-water cycle was compromised by the loss of 2-CP1/2 functions. The transcript levels of autophagy-related genes ATG5 and ATG7 were higher in plants with impaired 2-CP1/2 functions, and the formation of autophagosomes increased, together with an accumulation of oxidized and insoluble proteins. Silencing of ATG5 or ATG7 increased the levels of 2-CP transcripts and protein but decreased heat stress tolerance. These results demonstrate that 2-CPs fulfil a pivotal role in heat stress tolerance in tomato, via interactions with ascorbate-dependent pathways and autophagy.