The Mitochondrial Hsp90 Homolog PmTRAP1 Mediates Thermal Tolerance in the Papaya Mealybug, Paracoccus marginatus

The papaya mealybug, <i>Paracoccus marginatus</i>, a significant invasive pest in tropical and subtropical regions, exhibits a notable capacity to withstand high-temperature stress. To elucidate the molecular basis of this thermotolerance, we investigated the role of heat shock protein 90 (Hsp90) genes in this species. The full-length cDNA sequences of three <i>Hsp90</i> genes-<i>PmHsp90-1</i>, <i>PmHsp90-2</i>, and <i>PmTRAP1</i>-were cloned, subjected to bioinformatic analysis, and their expression profiles under heat stress were detected. RNAi-mediated suppression of <i>PmTRAP1</i> was conducted to evaluate survival under extreme high-temperature conditions. The open reading frames (ORFs) of <i>PmHsp90-1</i>, <i>PmHsp90-2</i>, and <i>PmTRAP1</i> are 2175 bp, 2178 bp, and 2085 bp in length, encoding proteins comprising 724, 725, and 694 amino acids, respectively. Phylogenetic and structural analyses confirmed that PmHsp90-1 and PmHsp90-2 are cytosolic isoforms, each containing a characteristic C-terminal MEEVD motif, while PmTRAP1 was identified as the mitochondrial isoform. All three genes were significantly upregulated under heat stress. RNAi-mediated knockdown of <i>PmTRAP1</i> markedly reduced the survival rate of <i>P. marginatus</i> under extreme high temperature. These findings demonstrate that <i>PmTRAP1</i> is essential for heat tolerance in the papaya mealybug. This study provides crucial insights into the molecular mechanisms of thermal adaptation in insects and identifies <i>PmTRAP1</i> as a potential target for future research on managing insect responses to environmental stress.