An analysis of variability in genome organisation of intracellular calcium release channels across insect orders

Using publicly available genomic data, combined with RT-PCR validation, we explore structural genomic variation for two major ion channels across insect classes. We have manually curated ryanodine receptor (RyR) and inositol 1,4,5-trisphosphate receptor (IP(3)R) ORFs and their corresponding genomic structures from 26 different insects covering major insect orders. We found that, despite high protein identity for both RyRs (>75%) and IP(3)Rs (~67%), the overall complexity of the gene structure varies greatly between different insect orders with the simplest genes (fewest introns) found in Diptera and the most complex in Lepidoptera. Analysis of intron conservation patterns indicated that the majority of conserved introns are found close to the 5′ end of the channels and in RyR around the highly conserved mutually exclusive splice site. Of the two channels the IP(3)Rs appear to have a less well conserved organisation with a greater overall number of unique introns seen between insect orders. We experimentally validated two of the manually curated ORFs for IP(3)Rs and confirmed an atypical (3799aa) IP(3)R receptor in Myzus persicae, which is approximately 1000 amino acids larger than previously reported for IP(3)Rs.