Thermal priming enhances yield after recurrent heat stress and involves SlHSFA2-SlERFs in the regulation of transcriptional thermal memory in tomato.

Heat stress (HS) severely limits plant growth and productivity, threatening agriculture and food security. Plants cope with recurrent HS through adaptive thermal memory, which allows them to retain a memory of prior moderate priming stress. However, while this process has been well studied in Arabidopsis thaliana, it remains unclear whether the same molecular mechanisms operate in horticultural crops such as tomato (Solanum lycopersicum). Here, we show that tomato plants display a longer thermal memory capacity than Arabidopsis. We found that thermal priming followed by recurrent HS enhanced yield of tomato plants under both controlled and field conditions. Consistent with previous reports, we show that HEAT SHOCK FACTOR A2 (SlHSFA2) is required for thermal priming, as hsfa2 CRISPR mutants lost priming capacity. SlHSFA2 acts as positive regulator of a subset of type II transcriptional thermal memory genes, including SlBAG6. SlHSFA2 physically interacts with ETHYLENE RESPONSE FACTORs, which function as co-activators of type II transcriptional thermal memory genes and further enhance the expression of those genes in response to heat. Together, these findings establish a regulatory module critical for heat adaptation in tomato.