Abstract: [Objective] The thermotolerance transcription factor HSF-1 adjusts various cellular processes in nematode, such as the cGMP, TGFβ-like and Insulin/IGF signaling pathways, in response to heat stress. The cloning and expression analysis of the heat shock transcription factor Bx-HSF-1 would contribute to a deep understanding of the molecular mechanism of thermotolerance in Bursaphelenchus xylophilus.[Method] The gene of Bx-HSF-1 was cloned with the method of PCR based on the genomic data of B. xylophilus. The bioinformatics analyses, such as Gene Ontology, phylogenetic and conserved domain analysis, were conducted to the amino acid sequence of Bx-HSF-1. The protein 3D structure and docking were analyzed to predict the target gene. The q-PCR was used to analyze the gene expression of Bx-HSF-1 and target gene. The gene expression location of Bx-HSF-1 was carried out by the method of in-situ hybridization.[Result] The CDS of Bx-HSF-1, which was 1 404 bp, was cloned based on the genomic data of B. xylophilus. The amino acid sequence of Bx-HSF-1 had a DNA binding domain and a bZip domain. The results suggested that Bx-HSF-1 would be involved in the biological process of response to heat, dauer larval development and defense response, and had the molecular function of sequence-specific DNA binding. The hydrophobicity analysis indicated that the DNA binding domain was a hydrophobic core, which was constructed by 3 α helices and 4 antiparallel β folds. Bx-DAF-7 was selected as the target gene of Bx-HSF-1, based on the genomic data. The data of transcriptome and Q-PCR indicated that heat shock or hypothermia promoted the expression of Bx-HSF-1, and suppressed the expression of Bx-DAF-7. The expression of Bx-HSF-1 was negatively correlated with the expression of Bx-DAF-7. The in-situ hybridization showed clear signals of Bx-HSF-1 at the isthmus and intestine.[Conclusion] This study showed that Bx-HSF-1 with a specific DNA sequence binding molecules function. Target gene prediction indicated that the dauer larval forming gene Bx-DAF-7 was the target gene of Bx-HSF-1. Transcriptome sequencing and q-PCR results showed that Bx-HSF-1 was negatively correlated with the expression of Bx-DAF-7. The expression of Bx-HSF-1 was located at neurons, body wall muscle cells and hypodermal cells.

Key words: Bursaphelenchus xylophilus, heat shock transcription factor, thermotolerance, hypothermia