Functional differentiation in bryozoan colonies: a proteomic analysis

Abstract

Bryozoans are typical modular organisms. They consist of repetitive structural units, the zooids. Bryozoan colonies grow by zooidal budding, with the distribution pattern of the budding loci underlying the diversity of colony forms. Budding is usually restricted to the colony periphery, where a “growing edge” or local terminal growth zones are formed. Non-budding parts of the colony can be functionally subdivided, too. In many species colonies consist of regular, often repetitive zones of feeding and non-feeding modules, associated with a periodical degeneration and regeneration of the polypide retractile tentacle crown with a gut and the accompanying musculature. The mechanisms of functional differentiation in bryozoan colonies are unknown. Presumably, budding and/or polypide recycling are induced or inhibited by certain determinants of functional specialization in different colony parts. An effective tool of their identification is the comparison of proteomes in functionally different zones. Here we report the results of proteomic analysis of three bryozoan species from the White Sea with a different colony form: Flustrellidra hispida, Terminoflustra membranaceotruncata and Securiflustra securifrons. Using differential two-dimensional electrophoresis (2D-DIGE), we compared proteomes of the growing edge, the zone with polypides and the zone without polypides. We assessed the general level of differences between the zones and revealed proteins whose relative abundance changed gradually along the proximal-distal colony axis. These proteins might be involved in the determination of the functional differentiation of the colony.