Malate decarboxylation in species belonging to different C4 subtypes inside the Panicoideae clade.

CALACE, P.; DRINCOVICH, M. F.; ANDREO, C. S.; GERRARD WHEELER, M.C.; SAIGO, M.

Congreso; RAFV XXXII; 2018

As an adaptation to changing climatic conditions thatcaused high rates of photorespiration, plants haveevolved the C4 pathway, which creates a CO2 pumpthat concentrates it around the RuBisCO. In most C4species, this is achieved through compartmentalizingthe initial and definitive CO2 assimilation processesinto two discrete cell types, namely mesophyll (M) andbundle sheath (BS) cells. As part of this mechanism acompound of four carbon atoms is transported from Mto BS cells. Setaria italica (foxtail millet) and Panicumvirgatum (switchgrass) are two members of the Panicoideaeclade used for feed and biofuel production.Despite their evolutionary closeness, they have beenclassified into different C4 subtypes as they possesesa NADP or NAD-dependent malic enzyme as major malatedecarboxylase within chloroplasts or mitochondriaof BS cells, respectively. In this study we characterizethe kinetic and structural properties that distinguisheach decarboxylase enzyme operating in both grasses.Furthemore, we carried out a comparative analysis inorder to identify the isoforms involved in the C4 cycleand to characterize the differences between the photosyntheticand the non-photosynthetic versions. Theseresults were compared with those of other species previouslystudied by our group.