PLANT PHYSIOLOGY , Vol 111, Issue 2 627-634, Copyright © 1996 by American Society of Plant Biologists
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DEVELOPMENT AND GROWTH REGULATION |
Developmental and Light-Regulated Expression of Individual Members of the Light-Harvesting Complex b Gene Family in Pinus palustris
W. Peer, J. Silverthorne and J. L. Peters
Department of Biology, University of California, Santa Cruz, California 95064
Angiosperms require light for multiple aspects of chloroplast development,
including chlorophyll synthesis and induction of expression of the mRNAs
encoding the major polypeptides of the light-harvesting complex of
photosystem II (Lhcb genes). In contrast, many conifers, including pines,
firs, and spruces, can accumulate chlorophyll and the light-harvesting
chlorophyll a/b-binding proteins of photosystem II in complete darkness. To
understand the factors responsible for the regulation of expression of
individual Lhcb mRNAs in the pine Pinus palustris, we have prepared
sequence-specific cDNA probes for each of three family members, Lhcb1*Pp1,
Lhcb2*Pp1, and Lhcb2*Pp2, and have studied the expression of two of these,
Lhcb1*Pp1 and Lhcb2*Pp2, in detail. The levels of expression of each
sequence were disparate, and Lhcb1*Pp1-encoded transcripts were the most
abundant in the light. Both Lhcb1*Pp1 and Lhcb2*Pp2 mRNAs were expressed in
stems and cotyledons, but Lhcb1*Pp1 mRNA was present at about 10-fold lower
levels in stems than in cotyledons, in contrast to Lhcb2*Pp2 mRNA, which
was expressed at higher levels in stems than in cotyledons. Both Lhcb1*Pp1
and Lhcb2*Pp2 mRNAs were absent in embryos but were expressed during
seedling development. The levels increased with age in both the light and
the dark and in both cases were about 2-fold higher in the light than in
the dark. Despite the expression of Lhcb1*Pp1 and Lhcb2*Pp2 mRNAs during
development in darkness, the levels of both mRNAs increased in dark-grown
seedlings given red light in the low fluence range within 2 h of treatment.
