Functional analysis by RNAi of an glutaredoxin gene in Helicoverpa armigera

Molecular and Biochemical Characterization of Salt-Tolerant Trehalose-6-Phosphate Hydrolases Identified by Screening and Sequencing Salt-Tolerant Clones From the Metagenomic Library of the Gastrointestinal Tract

The exploration and utilization of microbial salt-tolerant enzymatic and genetic resources are of great significance in the field of biotechnology and for the research of the adaptation of microorganisms to extreme environments. The presence of new salt-tolerant genes and enzymes in the microbial metagenomic library of the gastrointestinal tract has been confirmed through metagenomic technology. This paper aimed to identify and characterize enzymes that confer salt tolerance in the gastrointestinal tract microbe. By screening the fecal metagenomic library, 48 salt-tolerant clones were detected, of which 10 salt-tolerant clones exhibited stronger tolerance to 7% (wt/vol) NaCl and stability in different concentrations of NaCl [5%-9% (wt/vol)]. High-throughput sequencing and biological information analysis showed that 91 potential genes encoded proteins and enzymes that were widely involved in salt tolerance. Furthermore, two trehalose-6-phosphate hydrolase genes, namely, tre_P2 and tre_P3, were successfully cloned and expressed in Escherichia coli BL21 (DE3). By virtue of the substrate of p-nitrophenyl-α-D-glucopyranoside (pNPG) which can be specifically hydrolyzed by trehalose-6-phosphate hydrolase to produce glucose and p-nitrophenol, the two enzymes can act optimally at pH 7.5 and 30°C. Steady-state kinetics with pNPG showed that the K _M and K _cat values were 15.63 mM and 10.04 s^-1 for rTRE_P2 and 12.51 mM and 10.71 s^-1 for rTRE_P3, respectively. Characterization of enzymatic properties demonstrated that rTRE_P2 and rTRE_P3 were salt-tolerant. The enzymatic activity increased with increasing NaCl concentration, and the maximum activities of rTRE_P2 and rTRE_P3 were obtained at 4 and 3 M NaCl, respectively. The activities of rTRE_P2 increased by approximately 43-fold even after 24 h of incubation with 5 M NaCl. This study is the first to report the identification as well as molecular and biochemical characterization of salt-tolerant trehalose-6-phosphate hydrolase from the metagenomic library of the gastrointestinal tract. Results indicate the existence of numerous salt-tolerant genes and enzymes in gastrointestinal microbes and provide new insights into the salt-tolerant mechanisms in the gastrointestinal environment.

Delivery of gene-specific dsRNA by microinjection and feeding induces RNAi response in Sri Lanka weevil, Myllocerus undecimpustulatus undatus Marshall

BACKGROUND

RNA interference (RNAi) is widely used in entomological research for functional analysis of genes and is being considered as a new tool for insect pest management. Sri Lanka weevil (SLW) is a highly polyphagous pest of agronomically important plants, but currently only a few control methods are available for this insect.

RESULTS

In the present study, we evaluated the stability of candidate reference genes β-ACT, α-TUB, EF1-α, RPL12 and GAPDH, and identified EF1-α as the most reliable for gene expression normalization. Four target genes involved in different cellular processes, including Prosα2, RPS13, Snf7 and V-ATPase A were selected to evaluate whether RNAi response in SLW adults can be triggered by microinjection and oral feeding of their double-stranded RNAs (dsRNAs). Three days after injection of the dsRNAs for the target genes, their transcript levels were significantly reduced (up to 91.4%) when compared to the control. Additionally, weevils fed with the target dsRNAs showed significant decreases in gene transcript levels and significant mortality was observed in insects treated with Prosα2 and Snf7 dsRNAs (78.6 to 92.7%).

CONCLUSION

Our data demonstrate that microinjection and feeding of dsRNA produce a strong RNAi response in SLW, indicating that RNAi-based strategies could be explored to develop a selective and environmentally safe control method against SLW. © 2019 Society of Chemical Industry.

RNA interference-mediated knockdown of 3, 4-dihydroxyphenylacetaldehyde synthase affects larval development and adult survival in the mosquito Aedes aegypti

BACKGROUND

The cuticle is an indispensable structure that protects the mosquito against adverse environmental conditions and prevents pathogen entry. While most cuticles are hard and rigid, some parts of cuticle are soft and flexible to allow movement and blood-feeding. It has been reported that 3, 4-dihydroxyphenylacetaldehyde (DOPAL) synthase is associated with flexible cuticle formation in Aedes aegypti. However, the molecular function of DOPAL synthase in the ontogenesis of mosquito remains largely unknown. In this study, we characterized gene expression profiles of DOPAL synthase and investigated its functions in larvae and female adults of Aedes agypti by RNAi.

RESULTS

Our results suggest that the expression of DOPAL synthase is different during development and the transcriptional level reached its peak at the female white pupal stage, and DOPAL synthase was more highly expressed in the cuticle and midgut than other tissues in the adult. The development process from larva to pupa was slowed down strikingly by feeding the first-instar larvae with chitosan/DOPAL synthase dsRNA nanoparticles. A qRT-PCR analysis confirmed that the dsRNA-mediated transcription of the DOPAL synthase was reduced > 50% in fourth-instar larvae. Meanwhile, larval molt was abnormal during development. Transmission electron microscopy results indicated that the formation of endocuticle and exocuticle was blocked. In addition, we detected that the dsDOPAL synthase RNA caused significant mortality when injected into the female adult mosquitoes.

CONCLUSIONS

Our findings demonstrate that DOPAL synthase plays a critical role in mosquito larval development and adult survival and suggest that DOPAL synthase could be a good candidate gene in RNAi intervention strategies in mosquito control.