Influence of ozone on transgenic tobacco plants expressing reduced quantities of Rubisco

Abstract

RbcS-antisense transformed tobacco plants (Nicotiana tabacum cv. Petit Havana) expressing reduced quantities of Rubisco protein were used to examine the role of Rubisco quantity in determining ozone (O3) sensitivity. Transformed and wild-type plants were exposed to O3 in the greenhouse and in the field. Stomatal conductance, net photosynthesis and Rubisco protein quantity were measured at various times. Antisense-transformed genotypes responded to O3 by exhibiting rapid, severe foliar necrosis. The wild-type plants responded more slowly, exhibiting limited injury. Decreases in stomatal conductance, net photosynthesis or Rubisco quantity in plants exposed to Os were not observed in asymptomatic leaves. Total biomass was lower for the transformed genotypes and decreased in both genotypes after exposure to O3. Shoot-root ratio and specific leaf area were higher in the transformed genotypes and increased in both genotypes with exposure to O3. Measurements of intercellular airspace demonstrated the presence of larger intercellular spaces in the transformed plants. The indirect effects of the rbcS antisense transformation, including morphological changes in the leaf, probably rendered the transformed plants more sensitive to the oxidant. The decreased quantity of Rubisco is not thought to be directly related to increased O3 sensitivity in the transformed plants.