PLANT PHYSIOLOGY , Vol 108, Issue 2 777-785, Copyright © 1995 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Ozone-Induced Alterations in the Accumulation of Newly Synthesized Proteins in Leaves of Maize
M. E. Pino, J. B. Mudd and J. Bailey-Serres
Department of Botany and Plant Sciences, Statewide Air Pollution Research Center, and Environmental Toxicology Graduate Program, University of California, Riverside, California 92521
We examined the response of leaves of 3-week-old maize (Zea mays L.) to
short-term (5 h) fumigation with O3-enriched air (0, 0.12, 0.24, or 0.36
[mu]L/L). Older leaves and leaf tissue developed more severe visible damage
at higher external O3 concentrations. To investigate the immediate effect
of O3 exposure on the accumulation of newly synthesized leaf proteins,
leaves were labeled with [35S]methionine after 2 h and fumigated for an
additional 3 h. O3-induced alterations of leaf proteins were observed in a
concentration-dependent manner. There was a significant decrease in
[35S]methionine incorporation into protein at the highest O3 concentration.
Developmental differences in accumulation of de novo-synthesized leaf
proteins were observed when the leaf tip, middle, and basal sections were
labeled under 0 [mu]L/L O3, and additional changes were apparent upon
exposure to increasing O3 concentrations. Changes in leaf protein synthesis
were observed in the absence of visible leaf injury. Subcellular
fractionation revealed O3-induced alterations in soluble and
membrane-associated proteins. A number of thylakoid membrane-associated
proteins showed specific increases in response to O3 fumigation. In
contrast, the synthesis of a 32-kD polypeptide associated with thylakoid
membranes was reduced in response to O3 fumigation in parallel with reduced
incorporation of [35S]methionine into protein. Immunoprecipitation
identified this polypeptide as the D1 protein of photosystem II. A
reduction in the accumulation of newly synthesized D1 could have
consequences for the efficiency of photosynthesis and other cellular
processes.
