Overexpression of rice phytochrome A in tobacco seedlings modifies responsiveness but not competence to phytochrome
✍ Scribed by Karlheinz Emmler; Thomas Kretsch; Eberhard Schäfer
- Publisher
- Springer-Verlag
- Year
- 1996
- Tongue
- English
- Weight
- 845 KB
- Volume
- 199
- Category
- Article
- ISSN
- 0032-0935
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✦ Synopsis
To analyse the control of rice phytochrome A (phyA) overexpression (wild type or variously mutated) on gene regulation, transgenic tobacco lines overexpressing various rice phyA constructs were crossed with transgenic tobacco lines containing mustard Lhcbl or Chsl promoters fused to the uidA reporter gene (13-glucuronidase). It was demonstrated that the temporal pattern of competence to respond to phytochrome was not altered by rice phyA overexpression. Also, overexpression of rice phyA did not change the spatial pattern of gene expression. The responsiveness to red and far-red light, on the other hand, depended on the type of overexpressed rice phyA in a structure-function relation: the serine-to-alanine mutant mediated an enhanced response both under continuous red and far-red light, whereas the N-terminal deletion mutant showed a dominant negative effect under continuous far-red light and even after red light pulses. However, the effectiveness of rice phyA overexpression depended on the promoter construct and the developmental stage of the seedlings. The Lhcbl promoter also conferred 13-glucuronidase activity in etiolated seedlings. This dark expression could be decreased by a long-wavelength farred light pulse given early in development (24 h after sowing), indicating that this phenomenon is under the control of stable types of phytochrome.