Identification of the trehalose-6-phosphate synthase (tps) gene in desiccation tolerant and intolerant tardigrades

The non-reducing disaccharide trehalose is one of the molecules involved in anhydrobiosis, acting as bioprotectant of cells exposed to desiccation. The main biosynthesis pathway of trehalose involves a glycosyl-transferase, trehalose-6-phosphate synthase (TPS), encoded by a gene (tps) whose presence and characterization has been studied in different metazoans. The tps gene is here identified for the first time in Tardigrada in twelve species belonging to both Heterotardigrada and Eutardigrada. The tps gene is found in all semiterrestrial and anhydrobiotic species examined, correlating trehalose presence with anhydrobiotic ability. In contrast, tps is not detected in two limnic and desiccation intolerant species. The surprising presence of tps in another limnic and desiccation intolerant species, Dactylobiotus parthenogeneticus, allows us to infer that in tardigrades trehalose could be produced and involved, not just in anhydrobiosis, but also in the regulation of other biological functions, such as encystment. The analysis of nucleotide tps sequences shows a very high conservation of the gene inside the phylum Tardigrada, while amino acid sequences further support the relationship between Tardigrada and Pancrustacea.