Plant Physiol, January 2001, Vol. 125, pp. 266-277
Biliverdin Reductase-Induced Phytochrome Chromophore Deficiency
in Transgenic Tobacco1
Beronda L.
Montgomery,2
Keara A.
Franklin,2
Matthew J.
Terry,
Brian
Thomas,
Stephen D.
Jackson,
Marc W.
Crepeau, and
J. Clark
Lagarias*
Section of Molecular and Cellular Biology, University of
California, Davis, California 95616 (B.L.M., M.W.C., J.C.L.);
Horticulture Research International, Wellesbourne, Warwick CV35 9EF,
United Kingdom (K.A.F, B.T., S.D.J.); and School of Biological
Sciences, University of Southampton, Bassett Crescent East,
Southampton S016 7PX, United Kingdom (K.A.F., M.J.T.)
Targeted expression of mammalian biliverdin IX
reductase (BVR),
an enzyme that metabolically inactivates linear tetrapyrrole precursors
of the phytochrome chromophore, was used to examine the physiological
functions of phytochromes in the qualitative short-day tobacco
(Nicotiana tabacum cv Maryland Mammoth) plant. Comparative phenotypic and photobiological analyses of plastid- and
cytosol-targeted BVR lines showed that multiple phytochrome-regulated processes, such as hypocotyl and internode elongation, anthocyanin synthesis, and photoperiodic regulation of flowering, were altered in
all lines examined. The phytochrome-mediated processes of carotenoid and chlorophyll accumulation were strongly impaired in plastid-targeted lines, but were relatively unaffected in cytosol-targeted lines. Under
certain growth conditions, plastid-targeted BVR expression was found to
nearly abolish the qualitative inhibition of flowering by long-day
photoperiods. The distinct phenotypes of the plastid-targeted BVR lines
implicate a regulatory role for bilins in plastid development or,
alternatively, reflect the consequence of altered tetrapyrrole metabolism in plastids due to bilin depletion.
1
This work was supported in part by the U.S.
Department of Agriculture National Research Initiative Competitive
Grant (no. AMD 9801768 to J.C.L.), a Royal Society University Research
Fellowship (to M.J.T.), and a CASE Studentship from the Biotechnology
and Biological Sciences Research Council (to K.A.F.).
2
These authors contributed equally to the paper.
*
Corresponding author; e-mail jclagarias{at}ucdavis.edu; fax
530-752-3085.
© 2001 American Society of Plant Physiologists
