EFICIÊNCIA DO USO DE NITROGÊNIO EM PLANTAS TRANSGÊNICAS DE TABACO COM ALTO ACÚMULO DE PROLINA

Abstract

Increasing the nitrogen use efficiencyofcrop plants is a result of the improvement in the mechanisms involved in nitrogen uptake, translocation, assimilation and remobilization. In this study, tobacco plants with high accumulation of proline caused by the insertion of the VaP5CSF129Amutant gene under control of the constitutive promoter CaMV35S was used as a model to investigate the effect of overexpression of the transgene in the uptake and utilization of N. For this, an experiment was carried out in a completely randomized design, in a 2x5 factorial arrangement, with two genotypes (transgenic eventand untransformed control) and five levels of nitrogen fertilization (25, 50, 100, 200 and 400 kg N ha-¹), cultivated under greenhouse conditions. Plants were evaluated for height, number of leaves, dry mass, free proline content, nitrogencontent, total protein content and use of the applied N (efficiency of absorption -EAbs, efficiency of leaf utilization –EUtiland efficiency of plant use -EUN). The transgenic plantswith high proline accumulation were less efficient than the control plants in terms of nitrogen absorption (with lowerN levelsin root, leaves and wholeplant), which resulted in lower EAbs. There was no difference between the transgenic and control genotypesfor EUtil. However, the transgenic plants presented lower EUN in comparison tothe control plants. Our data showed thattransgenictobacco plants withhigh proline accumulation do not have potential for direct use in agricultural systems, since the alteration of the biochemical balance between the metabolisms of nitrogen and carbon did not result in plants with higher EUN.