AUTHOR=Moody Nicholas R. , Christin Pascal-Antoine , Reid James D. 

TITLE=Kinetic Modifications of C4 PEPC Are Qualitatively Convergent, but Larger in Panicum Than in Flaveria

JOURNAL=Frontiers in Plant Science

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2020.01014

DOI=10.3389/fpls.2020.01014

ISSN=1664-462X

ABSTRACT=<p>C<sub>4</sub> photosynthesis results from a set of anatomical features and biochemical components that act together to concentrate CO<sub>2</sub> within the leaf and boost productivity. This complex trait evolved independently many times, resulting in various realizations of the phenotype, but in all C<sub>4</sub> plants the primary fixation of atmospheric carbon is catalyzed by phosphoenolpyruvate carboxylase. Comparisons of C<sub>4</sub> and non-C<sub>4</sub> PEPC from a few closely related species suggested that the enzyme was modified to meet the demands of the C<sub>4</sub> cycle. However, very few C<sub>4</sub> groups have been investigated, hampering general conclusions. To test the hypothesis that distant C<sub>4</sub> lineages underwent convergent biochemical changes, we compare the kinetic variation between C<sub>4</sub> and non-C<sub>4</sub> PEPC from a previously assessed young lineage (<italic>Flaveria</italic>, Asteraceae) with those from an older lineage found within the distantly related grass family (<italic>Panicum</italic>). Despite the evolutionary distance, the kinetic changes between the non-C<sub>4</sub> and C<sub>4</sub> PEPC are qualitatively similar, with a decrease in sensitivity for inhibitors, an increased specificity (<italic>k</italic><sub>cat</sub>/<italic>K</italic><sub>m</sub>) for bicarbonate, and a decreased specificity (<italic>k</italic><sub>cat</sub>/<italic>K</italic><sub>m</sub>) for PEP. The differences are more pronounced in the older lineage <italic>Panicum</italic>, which might indicate that optimization of PEPC for the C<sub>4</sub> context increases with evolutionary time.</p>