Genome-wide identification and expression characteristics of heat shock proteins in three rice planthopper species

Heat shock proteins (HSPs) are indispensable molecular chaperones that play critical roles in insects under various stress conditions. Previous studies have demonstrated that HSPs are involved in the growth, development, responses to abiotic stress, host interactions, and insecticide resistance in the three major rice planthoppers. In this study, we systematically identified and characterized the HSP gene family members in the brown planthopper (Nilaparvata lugens), the white-backed planthopper (Sogatella furcifera), and the small brown planthopper (Laodelphax striatellus). A total of 70, 55, and 86 HSP genes were identified in these three species, respectively. Phylogenetic analysis incorporating a large set of outgroup HSP genes revealed that rice planthopper HSPs can be classified into eight families: sHSP, CCT, HSP60, HSP10, DNAJ, HSP90, HSP70, and HSP100, with DNAJ being the most abundant. In contrast, HSP10, HSP60, HSP90, and HSP100 families each contained only 1~4 members. Substantial variation was observed in molecular weight, amino acid number, and protein sequence length among different HSP families, whereas members within the same family were relatively conserved. Collinearity analysis indicated that HSP family members exhibited highly similar chromosomal distributions across the three rice planthoppers. Systematic analysis of conserved motif and domain further showed that DNAJ family members possessed the greatest diversity of additional functional domains, whereas HSP70, HSP90, HSP10, CCT, and HSP60 families were highly conserved. Moreover, transcriptome-based expression profiling revealed distinct expression patterns of HSP genes across different developmental stages, tissues, and under temperature stress in the three planthopper species, which were further validated for selected HSP genes under different thermal conditions. Collectively, this study provides fundamental insights and valuable genetic resources for understanding the functional diversity, evolutionary dynamics, and ecological adaptation roles of the HSP gene families in planthoppers.