Transcription factor genes with expression correlated to nitrate‐related root plasticity of Arabidopsis thaliana

The root response to changes in nitrogen availability was examined in Arabidopsis thaliana. Plants grown on vertically oriented Petri plates with nutrient media containing either 10 or 0.5 mm KNO3 supplemented with 5 mm glutamine were analysed for changes in root architecture, morphology and nitrogen status compared to plants grown on 0.5 mm KNO3. Fourteen-day-old 10 mm KNO3-grown plants displayed a decrease in number, length and density of lateral roots, had the highest tissue NO3– content, but no change in amino acid composition. Lateral root development was arrested at a stage after the initiation of primordia but prior to emergence. In contrast, plants grown on 0.5 mm KNO3 supplemented with glutamine had a slightly higher number and density of lateral root primordia and lateral roots, lower root NO3– content, and higher tissue glutamine content. A macro-array containing 126 putative A. thaliana transcriptional factor expressed sequence tags was used to screen for regulatory genes with expression correlated to the root plasticity response. Genes for a basic leucine zipper (bZIP) and a LIM transcription factor were identified and via Northern analysis it was confirmed that their expression is preferentially observed in the roots and correlated to the root response to nitrate availability.