| Three nuclear genes encode glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in Arabidopsis thaliana. GAPA and GAPB encode chloroplast GAPDH, functioning in the Calvin cycle GAPC encodes cytosolic GAPDH, functioning in glycolysis. Regulation of the GAPDH genes was studied. GAPA and GAPB were regulated by light through both phytochrome and blue light receptor pathways GAPC was both developmentally and light regulated, and was induced by sucrose and hypoxia.Analysis of the phyA-101 mutant demonstrated that phytochrome A is necessary for GAPA and GAPB induction by far-red light. Analysis of the hy4-2.23N mutant showed that the HY4 gene product is required for full expression of GAPA and GAPB in response to continuous blue light. Light induction of GAPA and GAPB in norflurazon-treated seedlings grown under high fluence rate light was reduced and plastid differentiation was blocked, suggesting that a plastid signal participates in regulation of nuclear transcription of GAPA and GAPB.The GAPA gene promoter was analyzed in transgenic tobacco. Sequence elements sufficient to confer regulation by red, blue or white light occurred within the GAPC was highly expressed in a light-independent manner immediately following germination. While GAPA and GAPB expression was restricted to organs containing photosynthetic tissues, GAPC was expressed in all organs examined, including roots, flowers and leaves. GAPC was light regulated, probably through phytochrome, and was induced by sucrose and hypoxia, suggesting that multiple pathways functioned in its regulation.Mutagenized transgenic A. thaliana expressing... |
