Fine-mapping reveals BcNAC153 act as a negative regulator controlling high temperature tolerance in Brassica rapa

High temperature stress severely reduces yield and quality in cool-climate adapted NHCC vegetable crops. It is crucial to identify high temperature response regulating genes and analyze the molecular mechanisms of NHCC in order to develop heat-resistant varieties. Here, a whole genome resequencing was conducted on NHCC001, NHCC002, and 312 F₂ populations for QTLs mapping. A high-density bin-map containing 3608 bin markers was constructed covering 1156.88 cM, with an average adjacent interval of 0.32 cM. A major QTL for high temperature stress tolerance was identified in A01 chromosome, explaining 6.101% of phenotype variation. And BcNAC153, a NAC transcription factor, was captured and validated as a critical negative regulator for high temperature tolerance. The promoter activity of BcNAC153 was found to be regulated by high temperature, and BcMYB44 can inhibit the transcription of BcNAC153 by binding to the promoter of BcNAC153. In addition, this study reveals that BcCRK1 facilitates the ubiquitin-mediated degradation of BcNAC153, which affects the expression of downstream genes related to chlorophyll degradation, PCD, and ROS accumulation. Overall, this study sheds light on the molecular mechanisms underlying the response of NHCC to high temperature stress, and provides valuable insights for developing heat-resistant vegetable varieties.