Transcriptional regulation of a patatin-1 gene in potato.

Patatin is an abundant glycoprotein in the tubers of potato plants that has a lipid acyl hydrolase activity. Fusions of the promoter of patatin genes that are highly expressed in tubers with the reporter gene encoding beta-glucuronidase (GUS) have shown that patatin transcription has a high degree of tuber specificity. Patatin transcription was also inducible in other organs of transgenic potato by growth on high concentrations of sucrose. Experiments were conducted to define regions of the patatin promoter that confered tuber specific expression and sucrose inducibility. Sequences between -40 and -400 bp and between -400 and -957 bp of the transcriptional start site were able to confer tuber-specific expression on a heterologous truncated promoter. The cell specificity of GUS transcription in the transformants indicated that organ specificity was possibly determined by source-sink relationships of sucrose, or a metabolite of sucrose, in the whole plant.