PLANT PHYSIOLOGY , Vol 107, Issue 2 593-602, Copyright © 1995 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Light-Regulated and Organ-Specific Expression of Types 1, 2, and 3 Light-Harvesting Complex b mRNAs in Ginkgo biloba
E. Chinn, J. Silverthorne and A. Hohtola
Department of Biology, University of California, Santa Cruz, California 95064
In a prior study (E. Chinn and J. Silverthorne [1993] Plant Physiol
103:727-732) we showed that the gymnosperm Ginkgo biloba was completely
dependent on light for chlorophyll synthesis and chloroplast development
and that expression of light-harvesting complex b (Lhcb) mRNAs was
substantially increased by light. However, dark-grown seedlings that were
transferred to constant white light took significantly longer than
angiosperm seedlings to initiate a program of photomorphogenesis and the
stems failed to green completely. We have prepared type-specific probes for
mRNAs encoding major polypeptides of light-harvesting complex II (Lhcb1,
Lhcb2, and Lhcb3) and have used these to analyze the expression of
individual Lhcb mRNAs during greening. All three sequences accumulated in
the top portions of dark-grown seedlings transferred to light, but, as was
seen previously for total Lhcb mRNAs, there was a transient, reproducible
decline in the levels of all three mRNAs after 4 d in the light. This
transient decrease in Lhcb mRNA levels was not paralleled by a decrease in
Chl accumulation. By contrast, there were significantly lower levels of all
three Lhcb mRNAs in the lower portions of greening dark-grown stems as well
as lower Chl levels. We conclude that although the tops of the plants have
the capacity to etiolate and green, Gingko seedling stems continue a
program of development into woody tissue in darkness that precludes
greening when the seedlings are transferred to the light.
