PLANT PHYSIOLOGY , Vol 113, Issue 3 787-794, Copyright © 1997 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Composition of Photosystem II Antenna in Light-Harvesting Complex II Antisense Tobacco Plants at Varying Irradiances
R. Flachmann
European Molecular Biology Laboratory, Meyerhofstrasse 1, D 69117 Heidelberg, Germany
Plants with genes coding for chlorophyll a/b-binding proteins of
light-harvesting complex II (LHCII) in antisense orientation (Lhcb) that
are characterized by severely reduced Lhcb transcript levels (below 10% of
wild type) do not show a bleached phenotype due to a specific loss of the
polypeptide. To produce such a phenotype, a conceptually different
antisense approach was tested with a dual-functional transcript encoding
the gene for hygromycin phosphotransferase and the transit sequence of
Lhcb1-2 in the antisense orientation. Using increasing concentrations of
hygromycin, transformants with Lhcb steady-state levels as low as 9% of
wild type were regenerated and grown in a growth chamber. Together with
Lhcb antisense plants obtained in an earlier study, these antisense plants
were analyzed biochemically for their photosystem II (PSII) antenna
composition under varying light conditions. All antisense plants showed a
characteristic low-irradiance-induced increase of their PSII antenna size
as determined by higher chlorophyll concentrations, an increased content of
LHCII, and a constant chlorophyll b-to-lutein ratio in comparison with
control plants. One to 5% of the total Lhcb transcript amount was
sufficient to allow unrestricted formation of the PSII antenna at low
irradiance, suggesting that LHCII biogenesis is not controlled primarily by
transcription.
