REGULATION OF MALATE DECARBOXYLATION IN SPECIES BELONGING TO DIFFERENT C4 SUBTYPES OF THE PANICOIDEAE CLADE

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

Córdoba

Congreso; XXXII Reunión Argentina de Fisiología Vegetal; 2018

Sociedad Argentina de Fisiología Vegetal

As an adaptation to changing climatic conditions that caused high rates ofphotorespiration, plants have evolved the C4 pathway, which creates a CO2 pumpthat concentrates it around the RuBisCO. In most C4 species, this is achieved through compartmentalizing the initial and definitive CO2 assimilation processes into two discrete cell types, namely mesophyll (M) and bundle sheath (BS) cells. As part of this mechanism a compound of four carbon atoms is transported from M to BS cells. Setaria italica (foxtail millet) and Panicum virgatum (switchgrass) are two members of the Panicoideae clade used for feed and biofuel production. Despite their evolutionary closeness, they have been classified into different C4 subtypes as they posseses a NADP or NAD-dependent malic enzyme as major malate decarboxylase within chloroplasts or mitochondria of BS cells, respectively. In this study we characterize the kinetic and structural properties that distinguish each decarboxylase enzyme operating in both grasses. Furthemore, we carried out a comparative analysis in order to identify the isoforms involved in the C4 cycle and to characterize the differences between the photosynthetic and the non-photosynthetic versions. These results were compared with those of other species previously studied by our group.