Double-Stranded RNA-Mediated Suppression of Trypsin-Like Serine Protease (t-SP) Triggers Over-Expression of Another t-SP Isoform in Helicoverpa armigera

Abstract

High diversity of digestive proteases is considered to be the key factor in the evolution of polyphagy in Helicoverpa armigera. Serine proteases (SPs) contribute ~85% of the dietary protein digestion in H. armigera. We investigated the dynamics of SP regulation in the polyphagous pest, H. armigera using RNA interference (RNAi). HaTry1, an isoform of SP, expressed irrespective of the composition of the diet, and its expression levels were directly proportional to the larval growth rate. Therefore, HaTry1 was silenced by delivering 10 and 20 μg concentrations of double-stranded RNA through semi-synthetic diet. This led to a drastic reduction in the target gene transcript levels that manifested in a significant reduction in the larval weight initially, but the larvae recovered in later stages despite continuous dsRNA treatment. This was probably due to the compensatory effect by over-expression of HaTry13 (31-folds), another isoform of SP. Phylogenetic analysis of H. armigera SPs revealed that the over-expressed isoform was closely related to the target gene as compared to the other tested isoforms. Further, silencing of both the isoforms (HaTry1 and HaTry13) caused the highest reduction in the larval weight and there was no larval growth recovery. These findings provide a new evidence of the existence of compensatory effect to overcome the effect of silencing individual gene with RNAi. Hence, the study emphasizes the need for simultaneous silencing of multiple isoforms.

Intestinal proteolytic profile changes during larval development of Anticarsia gemmatalis caterpillars

“…The fact that trypsin‐ like and chymotrypsin‐ like increased significantly from third to fourth and from fourth to fifth instar corroborates and confirms the results obtained by specific inhibitors. The results also show that trypsin‐ like enzymes are more efficient than chymotrypsin‐ like enzymes in the fifth instar, corroborating with previous studies that demonstrated the prevalence of this enzyme group in the fifth and sixth instar of Lepidoptera larvae (Sharifloo, Zibaee, Sendi, & Talebi, ; Sharath Chandra et al, ; Grover, Kaur, Gupta, Taggar, & Kaur, ). The activity of cysteine proteases was determined by means of the substrate PFLNA, and the results showed that the specific activity of this sub‐subclass decreased with time.…”

Stabilized Double-Stranded RNA Strategy Improves Cotton Resistance to CBW (Anthonomus grandis)

“…Interestingly, this approach has been proven effective for insects generally resistant to RNAi. Furthermore, in some cases, simultaneous delivery of two or more dsRNA fragments is performed to mitigate compensatory effects caused by variants in the same gene [ 88 , 89 , 90 ]. Notwithstanding, our understanding of how insects respond to multi-target dsRNAs is still insufficient.…”

Adaptation of Helicoverpa armigera to Soybean Peptidase Inhibitors Is Associated with the Transgenerational Upregulation of Serine Peptidases

“…In our results, at least 32 differentially methylated genes with regulatory functions were found in the genome of larvae exposed to SPIs, many of which raised intriguing questions (Table S2). However, the regulation of transcript synthesis of the digestive system may depend on several regulatory factors, including transcriptional and translational control processes [52][53][54].…”