Unravelling the contribution of Arabidopsis NADP-malic enzyme 1 during seed development

ARIAS, C. L.; BADIA, M. B.; GERRARD WHEELER, M. C.; PAVLOVIC, T.; DRINCOVICH, M. F.; SAIGO, M.; TORCOLESE, G.; ANDREO, C. S.

Corrientes

Congreso; XXXI Reunión Argentina de Fisiología Vegetal; 2016

Sociedad Argentina de Fisiología Vegetal

Arabidopsis thaliana has four NADP dependent malic enzymes, three of which have a confirmed cytosolic localization (ME1, ME2 and ME3). ME2 presents the highest expression level in all vegetative tissues, where is responsible for most of the NADP-ME activity measured. On the other hand, ME1 is almost undetectable during normal vegetative growth. In this work we demonstrate the importance of this isoform during seed maturation. Total malic enzyme activity increases in growing siliques along with ME1 transcript, which reaches levels higher than those for ME2 in the latest stages. Knockout me2 lines or even a triple mutant me2me3me4 showed almost no alteration in the total malic enzyme activity in mature seeds, in contrast with a me1 mutant line where the total activity drastically decreases. Besides, lines that express ME1-YFP show an intense YFP fluorescence in embryos in the latest maturation stages. No YFP fluorescence is observed in early stages of embryo development including those lines in which the construction was expressed under the control of a double 35SCAMV promoter, suggesting a tight expression control of this gene during embryogenesis. Germination rates and seed quality were also assayed in different lines to help unravel the role of NADP-ME1.