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Expression of Functional Oat Phytochrome a in Transgenic Rice

Richard C. Clough, Jorge J. Casal, Emily T. Jordan, Paul Christou and Richard D. Vierstra
Plant Physiology
Vol. 109, No. 3 (Nov., 1995), pp. 1039-1045
Stable URL: http://www.jstor.org/stable/4276897
Page Count: 7
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Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Expression of Functional Oat Phytochrome a in Transgenic Rice
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Abstract

To investigate the biological functions of phytochromes in monocots, we generated, by electric discharge particle bombardment, transgenic rice (Oryza sativa cv Gulfmont) that constitutively expresses the oat phytochrome A apoprotein. The introduced 124-kD polypeptide bound chromophore and assembled into a red- and far-red-light-photoreversible chromoprotein with absorbance spectra indistinguishable from those of phytochrome purified from etiolated oats. Transgenic lines expressed up to 3 and 4 times more spectrophotometrically detectable phytochrome than wild-type plants in etiolated and green seedlings, respectively. Upon photoconversion to the far-red-absorbing form of phytochrome, oat phytochrome A was degraded in etiolated seedlings with kinetics similar to those of endogenous rice phytochromes (half-life approximately 20 min). Although plants overexpressing phytochrome A were phenotypically indistinguishable from wild-type plants when grown under high-fluence white light, they were more sensitive as etiolated seedlings to light pulses that established very low phytochrome equilibria. This indicates that the introduced oat phytochrome A was biologically active. Thus, rice ectopically expressing PHY genes may offer a useful model to help understand the physiological functions of the various phytochrome isoforms in monocotyledonous plants.

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