A functional study of two dsRNA binding protein genes in Laodelphax striatellus

One of the key limiting factors for using RNA interference technology to develop new pest control practices is the toxicological effectiveness. In order to explore potential methods to improve the efficiency of RNAi in insects, we cloned two dsRNA binding proteins from Laodelphax striatellus and investigated their functions.

In this study, the genes homologous to the dsRNA binding proteins TRBP and STAU in L. striatellus were first cloned and designated as LsTRBP and LsSTAU. Using the chitinase gene Chi, which has been confirmed to have lethal effects when knocked down by RNAi, as a reporter, the functions of these two dsRNA binding proteins were then investigated by using dsRNA feeding. The results showed that feeding with dsChi alone caused significant lethal effects, with a mortality four-fold higher than that of the control, whereas feeding with dsTRBP or dsSTAU alone did not yield any significant lethal effects. When dsChi was fed in the mixture 1:1 with dsSTAU, it also resulted in high mortality, which was a little lower than feeding with dsChi alone, but not statistically significant. However, when fed in the 1:1 mixture with dsTRBP, the lethal effect of dsChi was completely eliminated. Further analysis of gene expression found that single dsRNA depressed only its own target gene. When treated in 1:1 mixture, dsSTAU or dsChi did not change significantly the depression of the other dsRNA, but dsTRAB counteracted almost all the effect of dsChi.

These results indicate that the loss of LsTRBP can significantly inhibit dsChi-mediated genetic interference. These findings not only suggest that the LsTRBP gene in L. striatellus plays an important role in regulating RNAi but also imply that the metabolic regulation of dsRNAs with respect to genetic interference in L. striatellus is similar to that in higher animal species.