Heat shock transcription factors regulate thermotolerance gene networks in tomato (Solanum lycopersicum) flower buds

Tomato (Solanum lycopersicum) is an important fruit and vegetable crop in worldwide. The fertility of tomato reproductive organs can be dramatically decreased when ambient temperatures rise above 35 °C, reducing tomato fruit yield. It is necessary to identify transcription factors (TFs) and target genes involved in heat stress response (HSR) signaling cascades in tomato flower buds to improve tomato plant thermotolerance. In this study, we profiled genes expressed in three developmental stages of tomato flower buds. Red and turquoise modules for heat stress (HS) were identified through gene co-expression network analysis, and the genes within these modules were enriched in HS-related pathways. By focusing on the TFs in the two modules, we identified several novel HSR-related TFs, including SlWRKY75, SlMYB117, and SlNAM. Furthermore, homology analysis illustrated a conserved signaling cascade in tomato. Lastly, we identified and experimentally validated four HSF-regulated genes, namely SlGrpE, SlERDJ3A, SlTIL, and SlPOM1, that likely modulate thermotolerance in plants. These results provide a high-resolution atlas of gene expression during tomato flower bud development under HS conditions, which is a valuable resource for uncovering potential regulatory networks associated with the HSR in tomato.