Impaired malate and fumarate accumulation due the mutation of tonoplast dicarboxylate transporter

Abstract

Malate is a central metabolite involved in a multiplicity of plant metabolic pathways, being associated with mitochondrial metabolism and playing significant roles n stomatal movements. Vacuolar malate transport has been characterized at the molecular level and is performed by at least one carrier protein and two channels in Arabidopsis vacuoles. The absence of the Arabidopsis thaliana tonoplast Dicarboxylate Transporter (tDT) in tdt knockout mutant was previously associated with an impaired accumulation of malate and fumarate in leaves. Here, we investigated the consequences of this lower accumulation on stomatal behaviour and photosynthetic capacity as well as ts putative metabolic impacts. Neither the stomatal conductance (g s ) nor the kinetic responses to dark, light or high CO 2 were highly affected in tdt plants. In addition, we did not observe any impact on stomatal aperture following incubation with either bscisic acid (ABA), malate or citrate. Further, an effect on photosynthetic capacity was not observed in the mutant lines. However, leaf mitochondrial metabolism was affected in the tdt plants. Levels of the intermediates of the tricarboxylic acid cycle were altered and increases in both light and dark respiration were observed. We conclude that manipulation of the tonoplastic organic acid transporter impacted mitochondrial metabolism, while the overall stomatal and photosynthetic capacity were unaffected.