Upregulation of heat shock transcription factors, Hsp70, and defense-related genes in heat shock-induced resistance against powdery mildew in cucumber

This study investigated heat shock-induced resistance (HSIR) against cucumber powdery mildew and confirmed the initial mechanism of HSIR prior to systemic acquired resistance. Heat shock treatment reduced the disease index of powdery mildew when the inoculation period was 24 h or less. HSIR increased the gene expression of Hsp70 12 h after the treatment, while the gene expression levels of POX and LOX6 increased 24 h after the treatment. Heat shock element (HSE) motifs were found in the promoter area of these target genes. The gene expression levels of HsfA2, HsfB1, and HsfB4 increased 6 h after heat shock. Therefore, upon heat stress, some heat shock transcription factors were activated to bind to HSEs and upregulate the transcription of Hsp70 and defense-related genes.