Suppressive subtractive hybridisation transcriptomics provides a novel insight into the functional role of the hypobranchial gland in a marine mollusc

The hypobranchial gland present in gastropods is an organ whose function is not clearly understood. Involved in mucus production, within members of the family Muricidae it is also the source of the ancient dye Tyrian purple and its bioactive precursors. To gain further insights into hypobranchial gland biology, suppressive subtractive hybridisation was performed on hypobranchial gland and mantle tissue from the marine snail Dicathais orbita creating a differentially expressed cDNA library. 437 clones were randomly sequenced, analysed and annotated and 110 sequences had their functions putatively identified. Importantly this approach identified a putative gene involved in Tyrian purple biosynthesis, an arylsulphatase gene. Confirmation of the upregulation of arylsulphatase in the hypobranchial gland compared to the mantle was demonstrated using quantitative real-time PCR. Other genes identified as playing an important role in the hypobranchial gland were those involved in mucus protein synthesis, choline ester regulation, protein and energy production. This study confirms that the hypobranchial gland is involved in the production of mucus secretion and also identifies it as a site of chemical interaction and biosynthesis. This study lays the foundation for a better understanding of the enzymatic production of Tyrian purple precursors within the gland.