Abstract
Among cytsolic ADP-ribose/NADH pyrophosphatases (AtNUDX2, 6, and 7) in Arabidopsis, AtNUDX6 prefers NADH to ADP-ribose as a physiological substrate and its expression is induced by pathogenic attacks. Here, we explored physiological role of AtNUDX6 in the immuno response. The expression levels of AtNUDX6 were increased by treatment with 0.5 mM salicylic acid (SA), but not by various stressful conditions, suggesting that AtNUDX6 is involved in the SA signaling. The expression of NPR1-dependent SA-induced genes (SAIGs) paralleled that of AtNUDX6 under normal conditions and SA treatment, while those of NPR1-independent SAIGs did not change together with expression of AtNUDX6. Furthermore, the expression of TRX-h5 (thioredoxin 5) which catalyzed SA-induced NPR1 oligomer-to-monomer reaction paralleled that of AtNUDX6 under normal conditions and SA treatment. An inverse correlation was observed between the levels of ICS1 and AtNUDX6 under both normal conditions and SA treatment. These findings indicated that AtNUDX6 positively regulates the NPR1-dependent SA signaling via modulation of the NADH metabolism in plant immune response.
