Phylogenetic tree of SERK proteins. Phylogenetic tree (unrooted) was constructed using protein sequences of several SERK genes from different plant species. NCBI (GenBank) accession numbers of SERK genes and SERK proteins included in this analysis are: N. attenuata: NaBAK1 (HM639279), NaSERK1 (HM639280); N. benthamiana: NbSERK3/BAK1 (CK291393); Arabidopsis thaliana: AtSERK1 (NP_177328), AtSERK2 (NP_174683), AtSERK3 (NP_567920), AtSERK4 (NP_178999), AtSERK5 (NP_179000); Solanum tuberosum: StSERK1 (ABO14172); Medicago truncatula: MtSERK1 (AAN64294); Oryza sativa: OsSERK1 (BAD86793); Zea mays: ZmSERK1 (CAC37638); ZmSERK2 (CAC37639).