Gene expression profile of Aedes aegypti females in courtship and mating

Abstract

Aedes aegypti is the most synanthropic and anthropophilic mosquito of Culicidae. This species always cohabits with humans and is extremely opportunistic. Vector dispersal is directly related to the ability of the females on successfully finding a mate in a generally patchy urban scenario. In the present work, we investigate transcriptional changes in Ae. aegypti females during the courtship process and after mating. We observe a substantial alteration in gene expression triggered just upon contact with Ae. aegypti males, which in turn was not fully correlated to the changes triggered by the contact. After analysing shared significant differentially regulated genes between conspecific contact and insemination, the major part of the observed transcriptomic change triggered by contact is reversed after mating, indicating an intermediary situation between naive and mating conditions that we hypothesize to be crucial for mating success. Upon contact, several chemosensory related genes are repressed, especially odorant binding proteins. Most of these genes return to higher expression rates after mating. None of these genes are significantly regulated by the encounter of a different species, Aedes albopictus. The results presented here might be applied to an innovative control approach focusing on the semiochemical systems of mosquitoes in an effort to disrupt undesirable host-insect interaction to reduce the risk of pathogen transmission to humans.

Figure 1

Experimental design. Workflow showing stage and condition when RNA from heads and thoraxes of Ae. aegypti females were sampled.

Figure 2

Principal component analysis (PCA) and heatmap of log expression values. Clustering methods using full log expression data set of the three replicates for four Ae. aegypti female conditions: Naive (naive), conspecific male’s contact (Aeg), hetero-specific male’s contact (Alb) and inseminated (Ins). (a) PCA of the three biological replicates of each condition. (b) Heatmap showing expression profile for 1,725 genes that were found to be significantly regulated in at least one of the comparisons using naive females as baseline condition. Expression values were normalized by genes. Clustering analysis was performed using Euclidean distances and complete linkage method.

Figure 3

Number of significant differentially expressed genes for all analyzed comparisons. The numbers inside the bars represent total counts of differentially regulated genes per comparison. Blue bar represents up-regulated genes, red bar represents down-regulated genes.

Figure 4

Correlation profile of gene log2FC between conspecific contact and insemination (a) and conspecific and heterospecific contact (b). Scatter plot comparison of log2FC values of shared DE genes (intersection of Venn diagrams) in both (Naive vs. Aeg) × (Aeg vs. Ins) (a) and (Naive vs. Aeg) × (Naïve vs. Alb) (b). The insets show Venn diagrams of shared significantly regulated genes. Red dots indicate genes that do not follow the overall correlation pattern observed (negative correlation in 4a; positive correlation in 4b).

Figure 5

Heatmap of log2FC of chemosensory related gene families. Black boxes represent significantly regulated genes in each comparison. Only genes that were found significantly regulated for at least one of the comparisons are shown. OBP – odorant binding protein; CSP – chemosensory protein; SNMP - sensory neuron membrane protein; IR – ionotropic receptor.