Molecular population genetics of the NADPH cytochrome P450 reductase (CPR) gene in Anopheles minimus

Roles of a newly lethal cuticular structural protein, AaCPR100A, and its upstream interaction protein, G12-like, in Aedes aegypti

Mosquitoes form a vital group of vector insects, which can transmit various diseases and filarial worms. The cuticle is a critical structure that protects mosquitoes from adverse environmental conditions and penetration resistance. Thus, cuticle proteins can be used as potential targets for controlling the mosquito population. In the present study, we found that AaCPR100A is a structural protein in the soft cuticle, which has flexibility and elasticity allowing insects to move or fly freely, of Aedes aegypti. RNA interference (RNAi) of AaCPR100A caused high mortality in Aedes aegypti larvae and adults and significantly decreased the egg hatching rate. Transmission electron microscopy (TEM) analysis revealed that the larval microstructure had no recognizable endocuticle in AaCPR100A-deficient mosquitoes. A yeast two-hybrid assay was performed to screen proteins interacting with AaCPR100A. We verified that the G12-like protein had the strongest interaction with AaCPR100A using yeast two-hybrid and GST pull-down assays. Knockdown of G12-like transcription resulted in high mortality in Ae. aegypti larvae, but not in adults. Interestingly, RNAi of G12-like rescued the high mortality of adults caused by decreased AaCPR100A expression. Additionally, adults treated with G12-like dsRNA were found to be sensitive to low temperature, and their eggshell formation and hatching were decreased. Overall, our results demonstrated that G12-like may interacts with AaCPR100A, and both G12-like and AaCPR100A are involved in Ae. aegypti cuticle development and eggshell formation. AaCPR100A and G12-like can thus be considered newly potential targets for controlling the Ae. aegypti mosquito.

Population genetic structure of the malaria vector Anopheles minimus in Thailand based on mitochondrial DNA markers

BACKGROUND

The malaria vector Anopheles minimus has been influenced by external stresses affecting the survival rate and vectorial capacity of the population. Since An. minimus habitats have continuously undergone ecological changes, this study aimed to determine the population genetic structure and the potential gene flow among the An. minimus populations in Thailand.

METHODS

Anopheles minimus was collected from five malaria transmission areas in Thailand using Centers for Disease Control and Prevention (CDC) light traps. Seventy-nine females from those populations were used as representative samples. The partial mitochondrial cytochrome c oxidase subunit I (COI), cytochrome c oxidase subunit II (COII) and cytochrome b (Cytb) gene sequences were amplified and analyzed to identify species and determine the current population genetic structure. For the past population, we determined the population genetic structure from the 60 deposited COII sequences in GenBank of An. minimus collected from Thailand 20 years ago.

RESULTS

The current populations of An. minimus were genetically divided into two lineages, A and B. Lineage A has high haplotype diversity under gene flow similar to the population in the past. Neutrality tests suggested population expansion of An. minimus, with the detection of abundant rare mutations in all populations, which tend to arise from negative selection.

CONCLUSIONS

This study revealed that the population genetic structure of An. minimus lineage A was similar between the past and present populations, indicating high adaptability of the species. There was substantial gene flow between the eastern and western An. minimus populations without detection of significant gene flow barriers.

Multilocus nuclear DNA markers reveal population structure and demography of Anopheles minimus

Utilization of multiple putatively neutral DNA markers for inferring evolutionary history of species population is considered to be the most robust approach. Molecular population genetic studies have been conducted in many species of Anopheles genus, but studies based on single nucleotide polymorphism (SNP) data are still very scarce. Anopheles minimus is one of the principal malaria vectors of Southeast (SE) Asia including the Northeastern (NE) India. Although population genetic studies with mitochondrial genetic variation data have been utilized to infer phylogeography of the SE Asian populations of this species, limited information on the population structure and demography of Indian An. minimus is available. We herewith have developed multilocus nuclear genetic approach with SNP markers located in X chromosome of An. minimus in eight Indian and two SE Asian population samples (121 individual mosquitoes in total) to infer population history and test several hypotheses on the phylogeography of this species. While the Thai population sample of An. minimus presented the highest nucleotide diversity, majority of the Indian samples were also fairly diverse. In general, An. minimus populations were moderately substructured in the distribution range covering SE Asia and NE India, largely falling under three distinct genetic clusters. Moreover, demographic expansion events could be detected in the majority of the presently studied populations of An. minimus. Additional DNA sequencing of the mitochondrial COII region in a subset of the samples (40 individual mosquitoes) corroborated the existing hypothesis of Indian An. minimus falling under the earlier reported mitochondrial lineage B.