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

The presence of the gene coding for trehalose-6-phosphate synthase (tps) was determined for the first time in Tardigrada in twelve species belonging to both Heterotardigrada and Eutardigrada. The tps gene was found in all semiterrestrial and anhydrobiotic species examined, correlating trehalose presence with anhydrobiotic ability. In contrast, tps was not detected in two limnic and desiccation intolerant species. The surprising presence of tps in another limnic and desiccation intolerant species, Dactylobiotus parthenogeneticus, allowed 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. Our findings, integrated with literature data, indicate that anhydrobiotic ability in tardigrades can depend on the combined action of numerous different molecules, only partially identified. With nucleotide tps sequences, it is impossible to infer phylogenetic relationships inside the phylum Tardigrada, while amino acid sequences further support the relationship between Tardigrada and Pancrustacea.