
%0 Journal Article
%A Dever, Louisa V. 
%A Bailey, Karen J. 
%A Leegood, Richard C. 
%A Lea, Peter J. 
%T Control of Photosynthesis in <emph type="2">Amaranthus edulis</emph> Mutants with Reduced Amounts of PEP Carboxylase
%J Functional Plant Biology
%D 1997/11/19
%V 24
%N 4
%P 469-476
%K 
%R https://doi.org/10.1071/PP97008
%U https://www.publish.csiro.au/paper/PP97008 
%X Mutants of the NAD-ME plant have been created using sodium azide. These contain reduced activities of PEP carboxylase ranging from 5 to 100% of wild-type. Those with greater than 50% of the wild-type PEPC content showed a lower maximum rate of photosynthesis and reduced carboxylation efficiency compared to the wild-type plants. The PEPC from these heterozygotes was less sensitive to malate inhibition than the PEPC of the wild-type plants and also had an increased phosphorylation state. Mutants containing 45 and 49% of wild-type PEPC exhibited a greater Amax than was observed for the 55, 66 and 70% mutants. We postulate that there is a compensatory mechanism that activates PEPC when the PEPC protein is less than 55% of the wild-type. Control coefficients were measured for PEP carboxylase from wild-type and heterozygous (55%) plants. Results suggest that activation of PEPC by phosphorylation and metabolites may be more an &#8216;on-off&#8217; switch than a means of fine adjustment of PEPC activity in response to varying factors such as PEPC content, CO2 or temperature changes. 
