Absorption kinetics and nitrogen fractions in rice as an expression of the OsDof26 transcription factor

Dof transcription factors can act as transcriptional activators or repressors in several biological processes unique to plants, however many of their physiological functions have not been explained. In this work, rice plants (Oryza sativa L.), expressing the transcription factor OsDof26, showed changes in uptake kinetics and nitrogen (N) metabolism when subjected to treatments of 0.2 and 2.0 mM ammonium (NH₄⁺) or nitrate (NO₃^-) in a nutrient solution. The experimental design was completely randomised, with four replications in a 2 × 2 × 2 factorial, two plants (nontransformed rice plants and the L24 strain of rice, expressing OsDof26; two sources of N (NO₃^- and NH₄⁺); and two dosages (0.2 and 2.0 mM). At 17 days after germination (DAG), the treatments were applied and nutrient solution was then collected at intervals of 30 minutes for 48 hours, in order to estimate the kinetic uptake parameters for N (V_max, K_mand C_min). At 19 DAG, the total fresh weight was obtained, with part of the material being stored to determine the soluble nitrogen fractions and soluble sugars. The L24 strain showed less growth of shoots and roots for all the treatments studied compared to the untransformed plant (WT - wild type). The lower influx of NO₃^-and NH₄⁺ in the L24 resulted in unfavourable kinetic parameters and lower levels of NO₃^-, NH₄⁺ and amino N, thereby affecting the N metabolism in the transformed plants.

Oryza sativa L.; Nitrogen fractions; Soluble sugars; Absorption kinetics