Draft Genome Sequencing of the Foxglove Aphid (aulacorthum Solani Kaltenbach), a Vector of Potato Viruses, Provides Insights on Virulence Genes

The foxglove aphid (or glasshouse potato aphid, Aulacorthum solani Kaltenbach) transmits serious potato viruses (potato virus Y, and potato leaf roll virus) which cause heavy yield losses. Our aim of this study was to preliminary analysis of draft genome sequence to uncover virulence genes in the aphid. The genome assembly size (316.39 Mb) was very close to its genome size (318.19 Mb) estimated by flow cytometry. The genome completeness (81.8%) was confirmed by the Benchmarking Universal Single Copy Orthologs (BUSCO) analysis indicating 14.90% transposable elements (TEs) in the genome. Of total 22,021 predicted genes, 16,610 were annotated with putative functions of other aphids mainly Myzus persicae, Acyrthosiphon pisum and Diuraphis noxia. We identified virulence genes such as defensive and detoxification genes, salivary genes and chemoreceptors, insecticide resistance genes, virus transmission genes, transcription factors and mitochondrial genes. Importantly, analysis of detoxification genes particularly 53 cytochrome P450s (CYPs) indicated involvement of 23 CYPs families in aphid genome. Further, GO and KEGG pathways analyses showed gene enrichment predominantly with molecular function and signal transduction, respectively. Phylogeny analysis revealed genetic divergence among 12 aphid species and Au. solani is closely related with M. persicae. Further, non-synonymous (Ka)/synonymous (Ks) substitutions (Ka/Ks) indicated positive selection for 6 (Ka/Ks > 1) and 122 (Ka/Ks = 0.5-1) single copy orthologous gene pairs between Au. solani and with the pea aphid. Thus, our preliminary draft genome analysis provides new insights of Au. solani to understand molecular basis of aphid biology, host-aphid interactions and adaptation mechanism.