AbstractIn C3 plants Phosphoenolpyruvate Carboxylase (PEPC) is primarily involved in the replenishment of intermediates from the Citric Acid Cycle that have been depleted during biosynthetic reactions. Antisense DNA technology has allowed the specific repression of the enzyme.
Three groups of plants were used in the study. Tobacco antisense genes under the control of a constitutive promoter (CaMV35S promoter),; Tobacco antisense with a promoter expressing only in mesophyll cells (Cab3 promoter); and a C4 Flaveria antisense gene
( Cab3 promoter).
It was found that PEPC antisense expression causes a suppression in growth, although individual plants showed varying degrees of repression. In the first part of the study it was found that Group A plants (short plants) showed a 30-40% reduction in chlorophyll levels and 25% fewer leaves than the Group B plants (tall plants) of the same line.
In all lines, except line 9 there was a 15-40% reduction in photosynthesis levels for the Group A plants compared to the Group B plants. Stomata! function was not affected in any of the lines.
The results from the PEPC activity assay showed repressed activity
(more than 30% below average) in some individuals. These low PEPC activity individuals showed varying levels of photosynthesis and height.
The amino acid analysis did not draw any conclusions, but indicated that in low PEPC individuals there is a disruption in the production of some amino acids.
The results of the study indicate that the role of phosphoenolpyruvate carboxylase in the growth and development of the C3 tobaf co plant is complex, and requires further study in order to gain a deeper understanding
|Date of Award||1993|