PnCcp, a Phytophthora nicotianae protein containing a single complement control protein module, is sorted into large peripheral vesicles in zoospores

Motile zoospores are instrumental in establishing infection in many species of Phytophthora and other pathogenic oomycetes. We have identified Phytophthora nicotianae complement control protein (PnCcp), a protein that occurs in the large peripheral vesicles in Phytophthora nicotianae zoospores. Phytophthora nicotianae PnCcp contains a single complement control protein module and has homologues in P. infestans, P. sojae and P. ramorum. Sequence analysis revealed that PnCcp is a single copy, intron-less gene. Unlike the promoters of other Phytophthora genes that have been described, the PnCcp promoter contains a putative non-canonical TATA box, a CT box-containing initiator element and a downstream promoter element. PnCcp was expressed at low levels in mycelia and germinated cysts but was significantly upregulated in sporulating hyphae and zoospores. Immunolocalisation studies in zoospores and sporangia showed that PnCcp colocalised with LPV, a high molecular weight glycoprotein that is resident in the large peripheral vesicles. However, in mycelia arising from cysts that had germinated up to 3 days earlier, the two proteins did not colocalise, suggesting that the large peripheral vesicles may contain components that are processed separately during the asexual life cycle.