Figure 7
Nitrogen and lignin metabolisms and expression profile from genes-related under contrasting N fertilization treatments. Nitrate (NO3-) uptake is carried out by nitrate transporters (NRTs) and converted to nitrite (NO2-) by the nitrate reductase (NR) and in the plastid reduced to ammonium (NH4+). The NH4+ is incorporated by glutamine synthethase/glutamate synthase (GS2/GOGAT) into the amino acids. Cells in N deficiency and undergoing active lignification use an efficient N recycling mechanism where the NH4+ liberate by phenylalanine-ammonia lyase (PAL) and/or glutamate dehydrogenase (GDH) deamination by glutamate are incorporate by a cytosolic glutamine synthethase (GS1) and recycle into phenylalanine via Arogenate. Under N deficiency, high rates of lignification are maintained by the flux of N recycled. Expression profile by pairwise comparison between limiting (N-) and both luxuriant (N + and NO3) treatments; * = P < 0.01.