Author:
Dever Louisa V.,Bailey Karen J.,Leegood Richard C.,Lea Peter J.
Abstract
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 ‘on-off’ switch
than a means of fine adjustment of PEPC activity in response to varying
factors such as PEPC content, CO2 or temperature
changes.
Subject
Plant Science,Agronomy and Crop Science
Cited by
38 articles.
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