Natural variation in Arabidopsis adaptation to growth at low nitrogen conditions.

Improving nutrient use efficiency of crop plants, especially at low input, is essential to ensure sustainable food production in the future. In order to address the genetic basis of nutrient use efficiency in a model system, growth of Arabidopsis ecotypes at normal and low nitrogen (N) supply was compared. The ecotypes differed significantly in the extent of growth reduction in limiting conditions. The fresh weight of Shahdara and Ws grown at 1mM nitrate was reduced by 30% compared to control, whereas Col-0 and Ga-0 were almost unaffected. Total N content was reduced in all ecotypes by 10-30%. The capacity to store nitrate correlated with the tolerance to low N; in Shahdara and Ws, but not in Col-0 and Ga-0, nitrate content on low N was significantly reduced compared to control nutrition. The mRNA levels for genes of nitrate uptake and assimilation were only moderately affected by the treatment. The transcript levels of nitrate reductase NIA1 and nitrite reductase were higher in the ecotypes tolerant to low N (Col-0 and Ga-0) with normal N nutrition but on low N they were reduced to a much higher extent than the sensitive ecotypes (Shahdara and Ws). It seems that a higher capacity to keep nitrate reserves at low N, perhaps due to the ability to turn down nitrate reduction rate, is responsible for a better tolerance of Col-0 and Ga-0 to low N supply.