Description of Ribosome Inactivating Proteins encoding genes in Aedes aegypti species

LAPADULA WJ; MARCET P; TARACENA M; MASCOTTI ML; JURI AYUB M; LENHART A

Jornada; XI Jornadas regionales sobre mosquitos; 2018

Ribosome inactivating proteins (RIPs) are RNA N-glycosidases that depurinate a specific adenine residue in the conserved sarcin/ricin loop (SRL) of 28S rRNA. The SRL is a primary component of the ribosomal elongation-cycle machinery and their depurination inhibits the protein synthesis. The occurrence of RIP genes has been described in a wide range of plant taxa, as well as in several species of bacteria and fungi. A remarkable case is the presence of these genes in metazoans, as they seem to exclusively occur in mosquitos from the Culicinae subfamily. Recently, we reported that these genes are derived from a single and ancient horizontal gene transfer event from a bacterial gene donor. Moreover, we found evidence that mosquito RIP genes are evolving under purifying selection, are actively transcribed into RNA, and the RNAs are polyadelinated, suggesting these alien genes are playing a functional role within the Culicinae mosquitoes.In the present work, we amplified and sequenced three Aedes aegypti RIP genes (RIPAe1, RIPAe2 and RIPAe3) from individual specimens collected in 14 countries across the world. Then, haplotype diversity, presence of null alleles and genetic diversity were analyzed and correlated with the geographic origin of the samples. We identified relationships between genetic variability and mRNA expression patterns. The results indicate the existence of variability for these genes within Ae. aegypti. We confirm the presence of deleterious mutations although they are not fixed at the species level. These results support the hypothesis of functionality for these genes in mosquitoes. Our study provides a strong basis for future work on the molecular characterization of these alien genes and to understand how they have acquired functionality in mosquitos after the transfer event.