PLANT PHYSIOLOGY , Vol 112, Issue 2 569-574, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Effect of CO2 Concentration on Carbonic Anhydrase and Ribulose-1,5-Bisphosphate Carboxylase/Oxygenase Expression in Pea
N. Majeau and J. R. Coleman
Department of Botany, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada M5S 3B2
The effect of external CO2 concentration on the expression of carbonic
anhydrase (CA) and ribulose-1,5-bisphosphate carboxylase/oxygenase
(Rubisco) was examined in pea (Pisum sativum cv Little Marvel) leaves.
Enzyme activities and their transcript levels were reduced in plants grown
at 1000 [mu]L/L CO2 compared with plants grown in ambient air. Growth at
160 [mu]L/L CO2 also appeared to reduce steady-state transcript levels for
rbcS, the gene encoding the small subunit of Rubisco, and for ca, the gene
encoding CA; however, rbcS transcripts were reduced to a greater extent at
this concentration. Rubisco activity was slightly lower in plants grown at
160 [mu]L/L CO2, and CA activity was significantly higher than that
observed in air-grown plants. Transfer of plants from 1000 [mu]L/L to air
levels of CO2 resulted in a rapid increase in both ca and rbcS transcript
abundance in fully expanded leaves, followed by an increase in enzyme
activity. Plants transferred from air to high-CO2 concentrations appeared
to modulate transcript abundance and enzyme activity less quickly. Foliar
carbohydrate levels were also examined in plants grown continuously at high
and ambient CO2, and following changes in growth conditions that rapidly
altered ca and rbcS transcript abundance and enzyme activities.
