Phylogeny and distinct properties of major intrinsic proteins in the genomes of six Phytophthora species suggest their novel functions in Phytophthora

Major intrinsic proteins (MIPs), commonly known as aquaporins, transport water and other non- polar solutes across membranes. MIPs are believed to be involved in host-pathogen interactions. Herein, we identified 17, 24, 27, 19, 19, and 22 full-length MIPs, respectively, in the genomes of six Phytophthora species, P. infestans, P. parasitica, P. sojae, P. ramorum, P. capsici, and P. cinnamomi, which are devastating plant pathogens and members of oomycetes, a distinct lineage of fungus-like eukaryotic microbes. Phylogenetic analysis showed that the Phytophthora MIPs (PMIPs) formed a completely distinct clade from their counterparts in other taxa and were clustered into nine subgroups. Sequence and structural analysis of homology models indicated that the primary selectivity-related constrictions, including aromatic arginine (ar/R) selectivity filter and Froger9s positions in PMIPs were distinct from those in other taxa. The substitutions in the conserved Asn-Pro-Ala motifs in loops B and E of many PMIPs were also divergent from those in plants. We further deciphered group-specific consensus sequences/motifs in different loops and transmembrane helices of PMIPs, which were distinct from those in plants, animals, and microbes. The data collectively supported the notion that PMIPs might have novel functions and could be considered attractive anti-Phytophthora targets.