Evolutionarily conserved thaumatins are present in pea aphids and plants. (a) The three-dimensional structure of the pea aphid thaumatin ACYPI009605 (top) was calculated using the published crystallographic structure of a sweet cherry (plant) thaumatin 2AHN_A (bottom)  and Swissmodel , revealing that both thaumatins are similar in structure. However, one exposed loop, encircled by a dotted line, shows a significant difference in structure, suggesting possible adaptation to different targets. (b) Similarities are also revealed in the alignment of the pea aphid thaumatin with the plant thaumatin. A predicted signal sequence of the pea aphid thaumatin is underlined. Identical amino acids are highlighted in red. (c) Maximum likelihood phylogeny of thaumatins, indicating branches leading to nematode, plant, insect and bacteria-specific clades. Red highlights the sweet cherry thaumatin. Blue highlights the pea aphid thaumatins. Asterisks indicate approximate likelihood ratio test support >80. Abbreviations: Api, A. pisum; Cac, Catenulispora acidiphila; Cel, Caenorhabditis elegans; Mtr, Medicago truncatula; Pav, Prunus avium; Tca, Tribolium castaneum; Tpr, Trifolium pretense.