Seven transcripts from the chitinase gene family of the mud crab Scylla paramamosain: Their expression profiles during development and moulting and under environmental stresses.

Abstract: In crustaceans, chitinases (Chts) play crucial roles in physiological functions such as chitinous food digestion, moulting and stress responses. Chitinases have been identified in both prokaryotes and eukaryotes, but the composition and number of Cht family members vary across species, especially in crustaceans. Seven Cht transcripts, all of which contained the conserved enzyme activity motif, were cloned from Scylla paramamosain for the first time, and SpCht1‐SpCht6 were clearly classified into groups 1–6, respectively, through phylogenetic analysis. Notably, SpCht7, which had two catalytic domains, was identified for the first time in crabs and crustaceans. Although SpCht7 could not be grouped into any known Cht subclasses, it clustered together with insect Cht7 and could be classified into a novel subclass that we named group 7. The tissue distributions of SpChts, as well as their expression profiles during embryonic and larval development, growth‐related moulting, salinity and cadmium stresses, were also investigated. The results suggested that SpChts might have different and varied biological functions. These results would be helpful for understanding and clarifying the roles of chitinases in crab development, moulting and responses to environmental stress. These results also provide new insight into the origin and evolution of the chitinase gene family in crabs and other crustaceans. [ABSTRACT FROM AUTHOR]