Plant response to nitrate starvation is determined by N storage capacity matched by nitrate uptake capacity in two Arabidopsis genotypes.
In a low-input agricultural context, plants facing temporal nutrient deficiencies need to be efficient. By comparing the effects of NO(3)(-)-starvation in two lines of Arabidopsis thaliana (RIL282 and 432 from the Bay-0xShahdara population), this study aimed to screen the physiological mechanisms allowing one genotype to withstand NO(3)(-)-deprivation better than another and to rate the relative importance of processes such as nitrate uptake, storage, and recycling. These two lines, chosen because of their contrasted shoot N contents for identical shoot biomass under N-replete conditions, underwent a 10 d nitrate starvation after 28 d of culture at 5 mM NO(3)(-). It was demonstrated that line 432 coped better with NO(3)(-)-starvation, producing higher shoot and root biomass and sustaining maximal growth for a longer time. However, both lines exhibited similar features under NO(3)(-)-starvation conditions. In particular, the nitrate pool underwent the same drastic and early depletion, whereas the protein pool was increased to a similar extent. Nitrate remobilization rate was identical too. It was proportional to nitrate content in both shoots and roots, but it was higher in roots. One difference emerged: line 432 had a higher nitrate content at the beginning of the starvation phase. This suggests that to overcome NO(3)(-)-starvation, line 432 did not directly rely on the N pool composition, nor on nitrate remobilization efficiency, but on higher nitrate storage capacities prior to NO(3)(-)-starvation. Moreover, the higher resistance of 432 corresponded to a higher nitrate uptake capacity and a 2-9-fold higher expression of AtNRT1.1, AtNRT2.1, and AtNRT2.4 genes, suggesting that the corresponding nitrate transporters may be preferentially involved under fluctuating N supply conditions.
Richard-Molard
Céline
C
INRA, UMR1091 Environnement et Grandes Cultures, F-78850 Thiverval Grignon, France. richardm@grignon.inra.fr
Krapp
Anne
A
Brun
François
F
Ney
Bertrand
B
Daniel-Vedele
Françoise
F
Chaillou
Sylvain
S
D017360:Arabidopsis / Q000235:genetics* / Q000378:metabolism*; D001693:Biological Transport, Active / Q000502:physiology; D002244:Carbon / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D009566:Nitrates / Q000378:metabolism*; D009584:Nitrogen / Q000378:metabolism*; D009587:Nitrogen Isotopes; D035261:Plant Components, Aerial / Q000254:growth & development; D013217:Starvation; D013997:Time Factors
D009566:Nitrates; D009587:Nitrogen Isotopes; D002244:Carbon; D009584:Nitrogen