Lotus-specific expansion in LPR1/LPR2 proteins. (A) The number of LPR1/LPR2 homologs in land plants. Homologs detected by Basic Local Alignment Search Tool against the genomes of land plants are represented by a box. A protein similarity network of those proteins is also shown; lotus proteins are represented as purple nodes, Arabidopsis proteins (LPR1 and LPR2) are represented as green nodes and other land plant proteins are represented as grey nodes. (B) Heatmap of COG2132 gene family member expression in lotus. Reads per kilo base per million (RPKM) values were log2 transformed, where blue correlates to high expression, and yellow to low expression. (C) A maximum-likelihood tree of LPR1/LPR2-like lotus proteins. Branch support was calculated using an Approximate Likelihood-Ratio Test. Lotus homologs are connected with a dashed bracket, whereas proteins whose genes are found in tandem on the genome are connected with a solid bracket. A detailed phylogeny of COG2132 members can be found in Figure S8 in Additional file 1.