PLANT PHYSIOLOGY , Vol 103, Issue 3 727-732, Copyright © 1993 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Light-Dependent Chloroplast Development and Expression of a Light-Harvesting Chlorophyll a/b-Binding Protein Gene in the Gymnosperm Ginkgo biloba
E. Chinn and J. Silverthorne
Department of Biology, University of California, Santa Cruz, California 95064
Unlike conifers, the gymnosperm Ginkgo biloba is dependent on light for
chlorophyll (Chl) synthesis and initiation of chloroplast development.
Dark-grown seedlings show complete etiolation, including no detectable Chl
accumulation, no leaf expansion, and increased hypocotyl elongation. When
dark-grown seedlings are placed in white light, Chl synthesis and leaf
expansion are initiated, but unlike angiosperms, which initiate rapid
photomorphogenesis, Ginkgo takes at least 1 week to change to a normal
light-regulated pattern of growth. A cDNA clone (pLhcb*Gb1) encoding a Chl
a/b-binding protein of light-harvesting complex II from Ginkgo mRNA has
been used as a probe for the expression of this family of mRNAs. We have
found that, in common with angiosperms but in marked contrast to pines,
Lhcb mRNA is expressed in a highly light-dependent manner. In addition to
being expressed in light-grown leaves, this sequence is also expressed in
the green tissues of immature seeds. The Lhcb mRNA appears during greening
in parallel with the onset of Chl synthesis. The complete sequence of
pLhcb*Gb1 has been determined and the deduced amino acid sequence was found
to be of type I based on comparison with signature sequences of angiosperm
and gymnosperm sequences.
