Abstract
Heat shock 70kDa proteins (HSP70s) and their cochaperones DNAJs are ubiquitous molecular chaperones, which function as the “HSP70/DNAJ machinery” in a myriad of biological processes. At present, a number of HSP70s have been classified in many species, but studies on DNAJs, especially in insects, are lacking. Here, we first systematically identified and characterized the HSP70 and DNAJ family members in the brown planthopper (BPH), Nilaparvata lugens, a destructive rice pest in Asia. A total of nine HSP70 and 31 DNAJ genes were identified in the BPH genome. Sequence and phylogenetic analyses revealed the high diversity of the NlDNAJ family. Additionally, spatio-temporal expression analysis showed that most NlHSP70 and NlDNAJ genes were highly expressed in the adult stage and gonads. Furthermore, RNA interference (RNAi) revealed that seven NlHSP70s and 10 NlDNAJs play indispensable roles in the nymphal development, oogenesis, and female fertility of N. lugens under physiological growth conditions; in addition, one HSP70 (NlHSP68) was found to be important in the thermal tolerance of eggs. Together, our results in this study shed more light on the biological roles of HSP70/DNAJ in regulating life cycle, coping with environmental stresses, and mediating the interactions within, or between, the two gene families in insects.
Highlights
Facing a complicated and changing environment, insects have evolved the ability to maintain cellular and protein homeostasis, which enhances their development and survival during normal growth and upon exposure to stress
Genes in the HSP70 family can be further classified into two subfamilies, namely, HSP70 and HSP110 [4], which function in the cytoplasm, mitochondrion, and endoplasmic reticulum (ER) [10]
A total of nine HSP70 and 31 DNAJ genes were identified from the brown planthopper (BPH) genome and transcriptome databases
Summary
Facing a complicated and changing environment, insects have evolved the ability to maintain cellular and protein homeostasis, which enhances their development and survival during normal growth and upon exposure to stress. One of the strategies to adapt to the changing environments is to regulate the synthesis of heat shock proteins (HSPs), known as the molecular chaperones [1,2]. HSPs are ubiquitously expressed in most cell types and almost all organisms [3]. HSPs can be divided into several classes according to their molecular mass, structural characteristics, and functions, including HSP100, HSP90, HSP70, HSP60, HSP40, and small HSPs [1]. Among those HSP families, heat shock 70 kDa proteins (HSP70s) are the most ubiquitous and evolutionarily conserved members [3,4,5,6]. Genes in the HSP70 family can be further classified into two subfamilies, namely, HSP70 and HSP110 ( referred to as HSPH) [4], which function in the cytoplasm, mitochondrion, and endoplasmic reticulum (ER) [10]
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