Cloning of stress tolerance gene in Torulaspora delbrueckii No. 3110

A cryptic plasmid (pSRY1) was found in Torulaspora delbrueckii No. 3110. A plasmid vector (pSRY21) was constructed by ligating it to pPR1-RIM-C ORF with a cycloheximide resistance gene (RIM-C). The transformation efficiency of the strain No. 3110 with pSRY21 by the protoplast-PEG method was increased by 3000-fold by treatment of the protoplasts with polylysine [poly(epsilon-L-lysine)]. Previously we have reported a mutant No. 3110, T1, which can neither assimilate nor accumulate trehalose. The mutant was salt- and temperature-sensitive. We cloned a DNA fragment from No. 3110, which, when introduced, complemented these mutant characters of T1. These results suggested an important role of metabolism of trehalose for the stress tolerance.