PROMOTER ANALYSIS OF A LIGHT-REGULATED GENE ENCODING HYDROXYPYRUVATE REDUCTASE, AN ENZYME OF THE PHOTORESPIRATORY GLYCOLATE PATHWAY

Hydroxypyruvate reductase (HPR) is a peroxisomal enzyme that catalyzes the NADH-dependent reduction of hydroxypyruvate to glycerate in the photorespiratory glycolate pathway. HPR gene expression in cucumber seedlings is organ-specific and light-regulated. A 5.7 kb fragment of cucumber genomic DNA containing the entire HPR-encoding gene, hpr-A, plus 1069 bp of 5' flanking sequence was introduced into tobacco, as was a construct consisting of the upstream region (positions -1069 to +43) of the hpr-A gene fused to the beta-glucuronidase (GUS) reporter gene. Both constructs were expressed in the transgenic plants in an organ-specific and light-dependent manner. A deletion analysis of the 5' flanking sequence of the hpr-A gene was conducted in transgenic tobacco. A construct in which the 5'-flanking region had been deleted to within 299 bases of the transcription start site was sufficient to confer a high level of light-regulated expression on the hpr-A gene in the transgenic plants. However, deletion to position -218 resulted in a substantial reduction in expression. The region between positions -299 and -218 contains sequences resembling the I box and G box elements that are associated with other light-regulated genes.