Unique venom proteins from Solenopsis invicta x Solenopsis richteri hybrid fire ants

Authors: Valles, Steven; OLIVER, JASON - Tennessee State University; ADDESSO, KARLA - Tennessee State University; Perera, Omaththage

Submitted to: Toxicon: X
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/3/2021
Publication Date: 5/7/2021
Citation: Valles, S.M., Oliver, J., Addesso, K., Perera, O.P. 2021. Unique venom proteins from Solenopsis invicta x Solenopsis richteri hybrid fire ants. Toxicon: X. 9-10:100065. https://doi.org/10.1016/j.toxcx.2021.100065.
DOI: https://doi.org/10.1016/j.toxcx.2021.100065

Interpretive Summary: The red and black imported fire ants are invasive species that were introduced into the United States between 1920 and 1930. These ants cause approximately US$6 billion in damage annually to livestock and agricultural production and pose a serious threat to human health. A hybrid form does not occur between these species in their South American native range. However, in the US, they do form a viable hybrid form that has continued to expand its range ever since it was discovered in 1988. While examining these hybrid ants for genetic introgression of parent venom proteins, USDA and Tennessee State University scientists discovered variants of the venom protein 2 that were unique to the hybrid. Data suggest that the hybrid may have a competitive advantage over either parent species, which could impact control efforts.

Technical Abstract: The Solenopsis venom protein 2 transcript was amplified, sequenced, probed, and analyzed from Solenopsis invicta x richteri hybrid ant colonies collected from across Tennessee to determine the extent of introgression of each parent allele (Solenopsis invicta venom protein 2 [Soli2] and Solenopsis richteri venom protein 2 [Solr2]). Chemotaxonomic analyses of venom alkaloids and cuticular hydrocarbons were used to categorize hybrid colonies and their relative relatedness to each parent species. Hybrid colonies were chosen randomly from each chemotaxonomic hybridization category, including “very near S. richteri,” “near S. richteri,” “near S. invicta,” and “very near S. invicta.” Lateral flow immunoassays for detection of the Soli2 and Solr2 venom proteins were largely in agreement with the chemotaxonomic analyses for the very near S. richteri (100% Solr2) and very near S. invicta (80% Soli2, 20% Soli2 and Solr2) groups, while Soli2 and Solr2 were detected in approximately equal proportions (60 and 40%, respectively) in the near S. invicta and near S. richteri chemotaxonomic groups. Analysis of amplicons from a sub-sample of these hybrid colonies (n = 3 ant colonies/group; 10 ants pooled ants/colony) revealed one sequence with 100% identity to Soli2 (accession L09560) and three unique sequences, which we identify as Solenopsis hybrid venom protein 2 (Solh2; accession MT150127), Solenopsis hybrid truncated venom protein 2 (Solh2Tr97; accession MT150129), and Solenopsis richteri venom protein 2, D to A change at position 69 (Solr2A69; accession MT150128). The predicted open reading frame for Solh2 and Solh2Tr97 revealed sequences unique to hybrid ants, with Solh2Tr97an alternatively spliced form. A third unique sequence, Solr2A69, is likely the correct sequence for Solr2, which appears to have been published previously with a sequencing error (accession P35776).