First echinoderm trehalase from a tropical sea cucumber (Holothuria leucospilota): Molecular cloning and mRNA expression in different tissues, embryonic and larval stages, and under a starvation challenge.

Trehalases are a group of enzymes that catalyse the conversion of trehalose to glucose, and they are observed in most organisms. In this study, the first echinoderm trehalase, designated Hl-Tre, was identified from a tropical sea cucumber, Holothuria leucospilota. The full-length cDNA of H. leucospilota trehalase (Hl-Tre) is 2461 bp in length with an open reading frame (ORF) of 1788 bp that encodes a 595-amino-acid protein with a deduced molecular weight of 67.95 KDa. The Hl-Tre protein contains a signal peptide at the N-terminal and a functional trehalase domain, which includes the signature motifs 1 and 2. The mRNA expression of Hl-Tre was ubiquitously detected in all selected tissues, with the highest level being detected in the intestine. By in situ hybridization (ISH), the positive Hl-Tre signals were observed in the brush borders of the intestinal mucosa. In embryonic and larval stages, the transcript levels of Hl-Tre decreased during embryonic development and increased after the pentactula stage. After a challenge of starvation, the intestinal Hl-Tre mRNA levels were observed to be first decreased and partially recovered thereafter. Overall, our study provided the first evidence for trehalase in echinoderms and showed that this enzyme was potentially linked to a trehalose metabolic pathway in sea cucumbers.