The allergenic protein Tha p 2 of processionary moths of the genus Thaumetopoea (Thaumetopoeinae, Notodontidae, Lepidoptera): Characterization and evolution

• Tha p 2 is a Ser-, Gly-, Cy-, and Leu-rich allergenic protein made by 3 α-helices and six β-barrels.
• The gene coding for Tha p 2 is intronless and in most species shows heterozygosity.
• Two isoforms of Tha p 2 are present in most Thaumetopoenae moths.
• Twenty different isoforms are present in Thaumetopoea wilkinsoni.
• The evolution of Tha p 2 has been shaped by a combination of positive and negative selection.

The allergenic Tha p 2 protein has been extracted recently from the urticating setae of the pine processionary moth Thaumetopoea pityocampa. In the present paper, we test for the occurrence of this protein in other Thaumetopoeinae, with a particular focus on members of the genus Thaumetopoea, as well as unrelated moth species, to better understand the physicochemical properties of the protein, the nature of encoding genes and their evolutionary history. Tha p 2 is encoded by the intronless gene Tha p 2 that is restricted to the processionary moths (Thaumetopoeinae, Notodontidae, Lepidoptera). Most of the species present two isoforms of Tha p 2 that can be interpreted as the result of heterozygosity in the single gene. The only exception is represented by Thaumetopoea wilkinsoni, in which 20 different isoforms occur in a single specimen, leading to the conclusion that, at least in this species, multiple copies of Tha p 2 exist. Serine, glycine, cysteine and leucine are abundant in Tha p 2, a protein well conserved among processionary moths. The predicted secondary structures of Tha p 2 indicate the presence of 3 α-helices and six β-barrels. Finally, the evolution of the gene and the protein was characterized by a combination of positive and negative selection, with the latter being more evident.