Preliminary Detection and Analysis of Hox Genes in the Bryozoans Membranipora Grandicella (Cheilostomata) and Tubulipora flabellaris (Stenolaemata)

Abstract

Although the phylogenetic position of bryozoans have always been subject to debate on the basis of other criteria such as morphological and developmental characters, However, recent molecular phylogeny tends to place them inside the lophotrochozoan assemblage among protostomes with annelids, mollusks, platworms, nemerteans, brachiopods, and others. The Hox genes present in all metazoans has to be a powerful tool for broad reconstruction of animal phylogeny. Up to date, for bryozoans, only one species of cheilostomes, that is Bugula neritina was detected and analysed. In this paper, the Hox genes in another cheilostomatous species Membranipora grandicella and a stenolaematous species Tubulipora flabellaris which commonly found in the seas of southeastern China was preliminary detetected and analysed, aiming to find their devlopmentary evolutionary information and retest their protostome affinity. PCR amplication were porformed and the PCR products were clone sequenced. For each species, fourty positive clones were selected randomly and the results showed that two different Hox gene clones was detected within both of them. From their homeobox sequences and those of other related animal groups obtained through GenBank, we reconstructed their neighbour-jioning phylogenetic trees. In addition, their homeodomain sequences were preliminary analysed compared with other lophotochozoan animals. Both the phylogenetic analyses and the characteristic sites of the homodomain indicated their lophotrozoan affinities.