Isolation and expression analysis of two stress-responsive sucrose-synthase genes from the resurrection plant Craterostigma plantagineum (Hochst.)

The enzyme sucrose synthase (UDP-glucose: D-fructose 2 alpha-glucosyltransf erase, EC 2.4.1.13) is a key enzyme in carbohydrate metabolism, catalyzing the reversible conversion of sucrose uridine-diphosphate into fructose and UDP-glucose. We report the molecular characterization of two classes of cDN A and genomic clones encoding sucrose synthase from Craterostigma plantagin eum Hochst., a resurrection plant in which the turnover of sucrose is consi dered to have an important role in the unique phenomenon of surviving desic cation. Sucrose-synthase transcript and protein levels are modulated by deh ydration and rehydration. In-situ hybridization revealed that transcripts p referentially accumulate in phloem tissues. Promoter analysis underlined a role for class-I sucrose-synthase genes in dehydration stress and in respon se to cis-abscisic acid. A DNA sequence motif common to class-I sucrose-syn thase and sucrose-phosphate-synthase genes was discovered.