Light Regulation of Hypocotyl Elongation and Greening in Transgenic Tobacco Seedlings That Over-Express Rice Phytochrome A

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Previous analysis of a transgenic tobacco line (BN1) that over-expressed rice phytochrome A (PhyA) indicated that the introduced PhyA was spectrally and biologically active [Kay et al. (1989) Plant Cell 1: 775, Nagatani et al. (1991) Proc. Natl. Acad. Sci. USA 88: 5207]. In the present study, we have further investigated responses of the BN1 plants to light. Fluence rate dependence analysis of the inhibition of hypocotyl elongation indicated that the response is biphasic. The amplitude of the low fluence rate component increased by 2 to 3 fold in the BN1 plants compared to the wild type. In contrast, the presence of rice PhyA did not alter the level of chlorophyll in the BN1 seedlings grown under the same light conditions. Ultrastructure studies showed that chloroplasts in the BN1 plants were not significantly different from those in the wild type plants, except that chloroplasts in the guard cells of the BN1 plants appeared to be more developed than those of the wild type plants. The fluence response analysis of the potentiation of chlorophyll accumulation indicated no significant difference between the BN1 and the wild type plants. Thus, the introduced rice PhyA greatly influenced hypocotyl elongation but did not significantly affect the greening process.
日本植物生理学会の論文