| Summary: | Hsp90 (heat shock protein 90) chaperone machinery is considered to be a key regulator of proteostasis under both physiological and stress growth conditions in eukaryotic cells. The high conservation of both the sequence and function of Hsp90 allows for the utilization of various species to explore new phenotypes and mechanisms. In this study, three Hsp90 homologs were identified in the brown planthopper (BPH), <i>Nilaparvata lugens</i>: cytosolic <i>NlHsp90</i>, endoplasmic reticulum (ER) <i>NlGRP94</i> and mitochondrial <i>NlTRAP1</i>. Sequence analysis and phylogenetic construction showed that these proteins belonged to distinct classes consistent with the predicted localization and suggested an evolutionary relationship between <i>NlTRAP1</i> and bacterial HtpG (high-temperature protein G). Temporospatial expression analyses showed that <i>NlHsp90</i> was inducible under heat stress throughout the developmental stage, while <i>NlGRP94</i> was only induced at the egg stage. All three genes had a significantly high transcript level in the ovary. The RNA interference-mediated knockdown of <i>NlHsp90</i> its essential role in nymph development and oogenesis under physiological conditions. <i>NlGRP94</i> was also required during the early developmental stage and played a crucial role in oogenesis, fecundity and late embryogenesis. Notably, we first found that <i>NlHsp90</i> and <i>NlGRP94</i> were likely involved in the cuticle structure of female BPH. Together, our research revealed multifunctional roles of Hsp90s in the BPH.
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