Fig. 3: Expansions, contractions and positive selection within IRs and ORs in termites. | Nature Ecology & Evolution

Fig. 3: Expansions, contractions and positive selection within IRs and ORs in termites.

From: Hemimetabolous genomes reveal molecular basis of termite eusociality

Fig. 3

a,b, IR (a) and OR (b) gene trees of 13 insect species. In each tree, only well-supported clades (support values > 85) that include B. germanica or termite genes are highlighted within the gene trees. The lengths of the coloured bars represent the number of genes per species within each of these clades. The red asterisk in a denotes the putative root of intronless IRs. c, The upper schematic diagram depicts the 2D structure of an IR, containing ligand-binding lobes (S1 and S2), transmembrane regions (TM1–3) and the pore domain (P). Below, the sequence of the domains along the peptide is represented, showing that the sites, which are under significant positive selection (red bars; codeml site models 7 and 8) within Blattodea IRs for M. natalensis (P < 1.7 × 10−10; likelihood-ratio test, 5 sequences, 413 aligned codons), are all situated within the ligand-binding lobes and on or around the putative ligand-binding sites (asterisks)86. d, The same representation for ORs, which include eight transmembrane regions. Positive selection was found for M. natalensis (P = 1.1 × 10−10; 5 sequences, 1,001 aligned codons) and C. secundus (P = 5.6 × 10−16; likelihood ratio test, 26 sequences, 1,913 aligned codons) of the orange clade, each at two codon positions within the second transmembrane region and at a third position within the carboxy-terminal extracellular region for M. natalensis.