Characterization of Heat Shock Protein Expression and Its Application to Temporal Gene Expression in the Nematode <i>Pristionchus pacificus</i>

Temporal gene expression systems are widely used to examine gene functions at specific developmental stages. The heat-inducible gene expression system, which uses a heat shock promoter with evolutionarily conserved heat shock elements, is used in temporal gene expression systems in many organisms. The nematode, Pristionchus pacificus, is a satellite model system comparable to Caenorhabditis elegans, with unique developmental traits but lacking genetic tools for assessing temporal gene expression. To establish a temporal gene expression system in P. pacificus, we investigated the genes that were highly induced by heat shock. RNA-sequencing analysis revealed many differentially expressed genes after a 2-h heat shock event. One of the highly induced genes, PPA12242, is an ortholog of C. elegans hsp-16.41, and transgenic animals harboring a reporter system have shown that the genomic fragment upstream of this gene can induce gene expression in response to heat shock. Using the PPA12242 promoter, gene expression can be induced at all larval stages, and some phenotypes appear to be vulnerable to heat stress. Taken together, we identified a potential heat shock promoter in P. pacificus that is applicable to the temporal gene expression system of this species.