Analyzing the role of the Aedes triseriatus inhibitor of apoptosis 1 gene in transovarial transmission of La Crosse virus
Date
2007
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Abstract
Aedes triseriatus is the primary vector of La Crosse virus (LACV) in North America. The following studies were performed using field collections to elucidate the role of the Ae. triseriatus inhibitor of apoptosis 1 gene (AtIAP1) in conditioning TOT and to compare LACV ovarian titers in field collected mosquitoes with several laboratory Ae. triseriatus strains.
Mitochondrial DNA from field collected Ae. triseriatus mosquitoes showed few genetic differences and suggested that mosquitoes from within the collection area exist as a panmictic population. Most importantly, polymorphisms conditioning TOT should be distributed throughout the collection area.
The AtIAP1 gene was amplified from field collected LACV +/- Ae. triseriatus mosquitoes. Sequence analysis revealed that this gene is highly polymorphic but that none of these polymorphisms appear to be involved in conditioning TOT of LACV. Besides being a highly polymorphic gene, AtIAP1 mRNAs contain variable sequences in the 5'UTR. Genomic analysis showed these variable sequences are followed by Drosophila splicing motifs suggesting that mRNA variants are produced by alternative splicing. Q-RT-PCR analysis revealed differences in mRNA variant expression profiles in Ae. triseriatus life stages and tissue types. Similar studies revealed that there are significantly lower levels of AtIAP1 mRNA variant 3 in TOT permissive and LACV infected Ae. triseriatus mosquitoes when compared to TOT refractory and LACY uninfected mosquitoes. These studies suggest that expression of AtIAP1 mRNA variant 3 may be involved in conditioning TOT.
Finally, LACV S-segment genome equivalents (GE) were quantified in the midguts and ovaries of transovarially infected TOT permissive, TOT refractory, AIDL colony, and field collected Ae. triseriatus mosquitoes. The most intriguing result is that a small proportion of the LACV infected field mosquitoes have LACV GE levels similar to laboratory strains. This result suggests that some females develop stabilized, high titered LACV infections and possibly play a more important role in LACV persistence in nature.
These studies have added to the short list of alternative splicing examples in arthropod disease vectors and suggest that AtIAP1 mRNA expression may play a role in conditioning TOT. These studies also lay the groundwork for determining the role of stably infected Ae. triseriatus mosquitoes in LACV persistence.
Mitochondrial DNA from field collected Ae. triseriatus mosquitoes showed few genetic differences and suggested that mosquitoes from within the collection area exist as a panmictic population. Most importantly, polymorphisms conditioning TOT should be distributed throughout the collection area.
The AtIAP1 gene was amplified from field collected LACV +/- Ae. triseriatus mosquitoes. Sequence analysis revealed that this gene is highly polymorphic but that none of these polymorphisms appear to be involved in conditioning TOT of LACV. Besides being a highly polymorphic gene, AtIAP1 mRNAs contain variable sequences in the 5'UTR. Genomic analysis showed these variable sequences are followed by Drosophila splicing motifs suggesting that mRNA variants are produced by alternative splicing. Q-RT-PCR analysis revealed differences in mRNA variant expression profiles in Ae. triseriatus life stages and tissue types. Similar studies revealed that there are significantly lower levels of AtIAP1 mRNA variant 3 in TOT permissive and LACV infected Ae. triseriatus mosquitoes when compared to TOT refractory and LACY uninfected mosquitoes. These studies suggest that expression of AtIAP1 mRNA variant 3 may be involved in conditioning TOT.
Finally, LACV S-segment genome equivalents (GE) were quantified in the midguts and ovaries of transovarially infected TOT permissive, TOT refractory, AIDL colony, and field collected Ae. triseriatus mosquitoes. The most intriguing result is that a small proportion of the LACV infected field mosquitoes have LACV GE levels similar to laboratory strains. This result suggests that some females develop stabilized, high titered LACV infections and possibly play a more important role in LACV persistence in nature.
These studies have added to the short list of alternative splicing examples in arthropod disease vectors and suggest that AtIAP1 mRNA expression may play a role in conditioning TOT. These studies also lay the groundwork for determining the role of stably infected Ae. triseriatus mosquitoes in LACV persistence.
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Subject
Aedes triseriatus
inhibitor of apoptosis
La Crosse virus
transovarial transmission
organismal biology
genetics
virology
entomology