Enzymatic control of anhydrobiosis-related accumulation of trehalose in the sleeping chironomid, Polypedilum vanderplanki.
Bottom Line: Although computational prediction indicated that the alternative splicing variants (PvTpsα/β) obtained encoded probable functional motifs consisting of a typical consensus domain of TPS and a conserved sequence of TPP, PvTpsα did not exert activity as TPP, but only as TPS.The translated product of the TREH ortholog (PvTreh) certainly degraded trehalose to glucose.Trehalose was synthesized abundantly, consistent with increased activities of TPS and TPP and suppressed TREH activity.
Affiliation: Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.Show MeSH
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Mentions: In Saccharomyces cerevisiae, trehalose synthase forms a heterotetramer with TPS1, TPS2, TPS3 and TSL1 subunits [42,43]. In the complex, the TPS3 and TSL1 subunits, both of which possess GT-20 and TrePP motifs without TPS or TPP activity, act as regulators [27,28,42–44]. In addition, the activity of TPS is enhanced by its aggregation, indicating that heteromeric and/or homomeric multimerization of the TPS–TPP complex should be important for the production of TPS activity . Similar to S. cerevisiae, other regulatory subunits might constitute the trehalose synthase complex in P. vanderplanki. No cDNAs homologous to TPS3 and TSL1 have been found thus far in the EST database of P. vanderplanki. Although we could not detect TPS activity in PvTPSβ (Fig. 5A), acceleration of its expression by desiccation (Fig. 7) suggests that the protein also plays a role in anhydrobiosis induction. PvTPSβ might act as a regulatory subunit, in a similar manner to TPS3 and TSL1, interacting with PvTPSα and PvTPP. The absence of enzymatic activity in PvTPSα/β proteins prepared by an in vitro transcription and translation system might be caused by the inappropriate interaction of components. If PvTPSα also possesses the same property as TPS in yeast, aggregation of PvTPSα caused by dehydration could lead to an enhancement of its activity en route to anhydrobiosis. Further investigation is required to answer these questions.
Affiliation: Anhydrobiosis Research Unit, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, Japan.