Using double-stranded RNA to explore the role of heat shock protein genes in heat tolerance in Bemisia tabaci (Gennadius)

Zhi-Chuang Lü,Fang-Hao Wan

doi:10.1242/jeb.047415

Abstract

The whitefly, Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) biotype B, is one of the most destructive invasive pests of field and glasshouse crops, and has a high tolerance to heat. Our previous work found that whitefly females are more heat tolerant than males. In the present study, real-time PCR and double-stranded RNA (dsRNA) methods were used to explore the role of heat shock protein (Hsp) genes in whitefly of both sexes; this provided further evidence of the mechanism underlying the differential heat tolerance abilities of females and males. The results showed that both hsp23 and hsp70 mRNA expression levels were higher in females than in males from 37.5 to 42°C, while at the extreme temperature of 44°C the hsp70 mRNA level was higher in males than in females. There was no significant difference in hsp90 mRNA expression between females and males under heat shock conditions. Furthermore, the survival rate of females fed hsp23 or hsp70 dsRNA significantly decreased following heat shock at 44°C for 1 h, but male survival rate was not significantly affected. Additionally, the survival rate of both females and males showed no significant change after they were fed with hsp90 dsRNA. Collectively, the present study shows that the optimum mRNA expression of Hsp genes in females promotes a higher survival rate under heat shock conditions; hsp23 and hsp70 play a key role for heat tolerance in females but not in males, and hsp90 shows no significant role in heat tolerance in either females or males. Further, our study indicates that feeding with dsRNA is an effective method by which to study gene function, and the simplicity of this approach opens the way for further research on gene function in different sexes and diverse groups of species.

Highlights

RNA interference (RNAi) is a post-transcriptional gene silencing mechanism through which targeted genes are silenced by the introduction of double-stranded RNA into living cells or organisms (Fire et al, 1998)
Rinehart and colleagues found that suppressing expression of either hsp23 or hsp70 resulted in the loss of heat tolerance in Sarcophaga crassipalpis non-diapausing pupae, and had a significant effect on the pupa’s ability to survive exposure to low temperature (Rinehart et al, 2007)
Heat tolerance test To determine the role of heat shock protein (Hsp) genes in the ability to survive heat shock exposure, we analysed the relationship between heat tolerance and Hsp mRNA expression

Summary

Introduction

RNA interference (RNAi) is a post-transcriptional gene silencing mechanism through which targeted genes are silenced by the introduction of double-stranded RNA (dsRNA) into living cells or organisms (Fire et al, 1998). Direct injection and oral delivery/feeding of dsRNA are the main methods used to initiate RNAi in insects, as demonstrated in Lepidoptera (Turner et al, 2006), Coleoptera (Araujo et al, 2006), Diptera (Misquitta and Paterson, 1999), Homoptera (Ghanim et al, 2007) and Hymenoptera (Zhou et al, 2008). Most of these studies have focused on the identification of gene function with regard to insect development (reviewed in Lü, 2008). Thermotolerance in Drosophila has been shown to be primarily due to Hsp (reviewed in Rutherford, 2003)

Methods

Discussion

Conclusion