Figure 2.

Topology of the maximum likelihood tree representing the phylogenetic relationships among the LRR-RK KDs and other eukaryotic kinases. The phylogenetic tree was generated from an alignment of the KDs (Additional file 4) of representative Arabidopsis and animal protein kinases, LRR-containing RKs and closely related receptors lacking TM domains and/or LRRs from Monosiga brevicollis (Monosiga, brown), Chlorella variabilis NC64A (Chlorella, greenish blue), Ectocarpus siliculosus (Ectocarpus, gray) and oomycetes (oomycetes, blue). Oomycete LRR-RKs, Monosiga LRR-RKs, Chlorella LRR-RKs and Ectocarpus LRR-RKs are included in the monophyletic receptor kinase group (RKG, red box), consisting of the plant receptor-like kinase (RLK) and animal cytoplasmic Pelle (forming the RLK/Pelle subfamily, green), receptor serine/threonine kinase (RSK, light blue), receptor tyrosine kinase (RTK, khaki) and Raf (Raf, pink) proteins. The RKG members are distinct from the other eukaryotic kinases. See Additional file 5 for the detailed phylogenetic tree.