Engineering Nicotiana tabacum for enhanced water use efficiency by the cell-type specific expression of maize NADP-malic enzyme

MAURINO, VERÓNICA G.; LARA, MARÍA V.; ANDREO, CARLOS S.; MÜLLER, GABRIELA L.; DRINCOVICH, MARÍA F.; OITAVÉN, PABLO AGUSTÍN

Congreso; Plant Biology 2017; 2017

The consumption of plant materials increases at a rapid pace to satisfy the demands of a growing population for food and feed; further accelerated by the use of plants for biofuel production. These growing demands can only be met with improvements in plant productivity at given irrigation rates. Here, we report a strategy to enhance water use efficiency in the C3 plant Nicotiana tabacum by simultaneously decreasing stomata conductance and increasing the export of photosynthetic products to the phloem, achieved through the cell-localized expression of a maize NADP-malic enzyme, driven by the Arabidopsis thaliana Potassium channel 1 promoter. The biochemical modifications in both guard cells and vascular tissue produced by the activity of maize NADP-malic enzyme, which catalyses the oxidative decarboxylation of malate in the presence of NADP, are traduced in important phenotypic modifications in the whole plant. Compared to wild type plants, the transgenic tobacco lines (ME1, ME3 and ME4) produce significantly more biomass per water used and flower earlier than wild type plants. The stomata of the transgenic lines exhibited reduced pore sizes compared to the wild type plants. Transgenic tobacco lines export sugars to the phloem at higher rate than wild type; leading to higher sucrose, glucose, and fructose levels in phloem exudates. Transgenic tobacco lines display significant high net CO2 fixation rate than wild type plants at CO2 levels over 400 μmol mol-1 and light intensity over 200 μmol m-2 s-1. The results presented in this work correspond to a novel and promising strategy for managing plant productivity and water usage, through the manipulation of stomata movement and sugar phloem loading in source organs