Expression patterns and promoter characteristics of the gene encoding Actinidia deliciosal-galactose-1-phosphate phosphatase involved in the response to light and abiotic stresses

The gene encoding l-galactose-1-phosphate phosphatase (GPP) plays a central role in ascorbic acid (AsA) biosynthesis in plants. Here, we report AsA contents, GPP expression, and functioning of its promoter in response to light, exogenous stress-signalling hormones, or abiotic stresses in kiwifruit (Actinidia deliciosa). To identify the upstream region of GPP required for promoter activity, we constructed a series of promoter deletion derivatives. Each construct was analyzed by Agrobacterium-mediated transient transformation in tobacco leaves after various treatments. Some correlation was observed between the relative levels of GPP mRNA and AsA contents when kiwi leaves were exposed to varying light conditions, treatment with ABA or SA, wounding, or a hypoxic environment. Analysis of a series of 5′ deletions in tobacco leaves indicated that the proximal area 390 bp from the transcription initiation site was needed for establishing both the constitutive and the induced patterns of expression. This promoter was induced by light or one of our abiotic treatments. These results suggest that GPP is regulated by light or abiotic stress and that it plays an important role in controlling AsA contents in kiwifruit.