Abstract
Numerous enzymes that digest carbohydrates, such as cellulases and chitinases, are present in various organisms (e.g., termites, nematodes, and so on). Recently, the presence of cellulases and chitinases has been reported in marine organisms such as urchin and bivalves, and their several roles in marine ecosystems have been proposed. In this study, we reported the presence of genes predicted to encode proteins similar to cellulases and chitinases in the genome of the coral Acropora digitifera, their gene expression patterns at various life stages, and cellulose- and chitin-degrading enzyme activities in several coral species (A. digitifera, Galaxea fascicularis, Goniastrea aspera, Montipora digitata, Pavona divaricata, Pocillopora damicornis, and Porites australiensis). Our gene expression analysis demonstrated the expressions of these cellulase- and chitinase-like genes during various life stages, including unfertilized eggs, fertilized eggs, zygotes, planula larvae, primary polyps and adults of A. digitifera. Agar plate assays confirmed cellulase and chitinase activities in the tissues extracted from adult branches of several coral species. These results suggested that corals are able to utilize cellulases and chitinases in their life histories.
Highlights
We identified two cellulase-like genes and two chitinase-like genes in the A. digitifera genome (Table 1)
Phylogenetic analysis supported that these cellulase- and chitinase-like genes were classified into the animal-origin group (Fig. 1)
Regarding the cellulase-like genes, two coral cellulase-like genes belonged to the GHF 9 group and were located adjacent to each other owing to high sequence similarity at the putative amino acid level
Summary
They are major energy sources, and monosaccharide derivatives constitute sugar chains on cell surfaces. Carbohydrate levels have been suggested to reflect food shortage (Rossi et al, 2006). Reef-building corals, which are the major calcifying organisms supporting the biodiversity of coral reef ecosystems (Roberts et al, 2002), are known to secrete mucus, which is mainly composed of carbohydrates (Wild et al, 2010) and is an important primary product in coral reefs (Wild et al, 2004). Corals are considered to utilize carbohydrates for maintaining their life histories and for high-degree use in material circulation in coral reef ecosystems. How corals use carbohydrates is not yet known
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