A bHLH transcription factor,CsSPT,regulates high-temperature resistance in cucumber

High-temperature stress threatens the growth and yield of crops. Basic helix-loop-helix(bHLH) transcription factors(TFs) have been shown to play important roles in regulating high-temperature resistance in plants. However, the bHLH TFs responsible for high-temperature tolerance in cucumbers have not been identified. We used transcriptome profiling to screen the high temperature-responsive candidate bHLH TFs in cucumber. Here, we found that the expression of 75 CsbHLH genes was altered under high-temperature stress. The expression of the CsSPT gene was induced by high temperatures in TT(Thermotolerant) cucumber plants. However, the Csspt mutant plants obtained by the CRISPR-Cas9 system showed severe thermosensitive symptoms, including wilted leaves with brown margins and reduced root density and cell activity.The Csspt mutant plants also exhibited elevated H_(2)O_(2) levels and down-regulated photosystem-related genes under normal conditions.Furthermore, there were high relative electrolytic leakage(REC), malondialdehyde(MDA), glutathione(GSH), and superoxide radical(O_(2)^(·-)) levels in the Csspt mutant plants, with decreased Proline content after the high-temperature treatment. Transcriptome analysis showed that the photosystem and chloroplast activities in Csspt mutant plants were extremely disrupted by the high-temperature stress compared with wildtype(WT) plants. Moreover, the plant hormone signal transduction, as well as MAPK and calcium signaling pathways were activated in Csspt mutant plants under high-temperature stress. The HSF and HSP family genes shared the same upregulated expression patterns in Csspt and WT plants under high-temperature conditions. However, most bHLH, NAC, and bZIP family genes were significantly down-regulated by heat in Csspt mutant plants. Thus, these results demonstrated that CsSPT regulated the high-temperature response by recruiting photosynthesis components, signaling pathway molecules, and transcription factors. Our results provide important insights into the heat response mechanism of CsSPT in cucumber and its potential as a target for breeding heat-resistant crops.

SmEGY3 mediates H_(2)O_(2) production to enhance high-temperature stress tolerance by activating the expression of SmCSD1 in eggplant

High temperature(HT)has major effects on the growth and production of vegetable crops,including eggplant(Solanum melongena L.).Eggplant seedlings,flower organs,and fruits are affected by high temperature stress(HTS).Nonetheless,key HT response factors are rare in eggplant.In this study,we found that SmEGY3 was localized in chloroplasts and nuclei,and the expression was induced by HT.We confirmed that SmEGY3 played a positive role in regulating heat tolerance of plants by virus-induced gene silencing(VIGS)and overexpression assays.Compared to the control plants,the SmEGY3-silenced plants showed significantly decrease in the H_(2)O_(2) content and H_(2)O_(2)-mediated retrograde signalling genes expression while the SmEGY3-overexpressing plants displayed significantly increase.