Fig. 4.

Cnidarian ficolin-like proteins (CniFLs), a newly recognized family of putative PRRs. (A) Maximum-likelihood phylogenetic tree of all CniFLs identified in Aiptasia and stony corals (A. digitifera and Stylophora pistillata) and of all canonical ficolins (Fcns) found in stony corals and the anemone N. vectensis (Dataset S1.7). A human and a mouse ficolin (one of three and two, respectively, in those species) were also included as an out-group. The tree is based on an alignment of a 113-amino-acid sequence (with gaps removed) that spans portions of the collagen and fibrinogen domains. Most of the identified CniFLs contain three central Ig domains, but five (indicated by an asterisk) contain only two. Numbers on nodes denote bootstrap values. (B) Components of the lectin-complement pathway that are encoded in the Aiptasia genome (based on KEGG analysis; SI Appendix, SI Materials and Methods) and may be involved in signaling downstream of the CniFLs. BF, complement factor B; C2, C3, and C3b, complement components 2 and 3 and the cleavage product of C3; C4BP, complement component 4 binding protein; CR, complement receptor; HF1, complement factor H; MASP, mannose-binding-lectin–associated serine protease. Complement component C4 was not unequivocally identified in the currently available sequence but is included here for the sake of completeness (Dataset S1.8).