Nitrogen and nitric oxide regulate Arabidopsis flowering differently

Area of Science:

• Plant Physiology
• Molecular Biology
• Circadian Rhythms

Background:

• Nitrogen (N) and nitric oxide (NO) are known to delay flowering in plants.
• Previous research implicated ferredoxin NADP+ oxidoreductase (FNR1) and cryptochrome 1 (CRY1) in nitrogen-regulated flowering time.
• The precise signaling mechanisms by which N and NO influence flowering time remain unclear.

Purpose of the Study:

• To investigate whether nitrogen and nitric oxide utilize the same signaling pathways to delay plant flowering.
• To elucidate the distinct roles of N and NO in regulating flowering time and the circadian clock.
• To examine the effect of sucrose supply on N- and NO-induced flowering delays.

Main Methods:

• Comparative analysis of flowering time under high nitrogen and nitric oxide treatments.
• Measurement of circadian clock gene transcript amplitudes under different treatments.
• Assessment of protein S-nitrosation modification on key flowering time regulators.
• Evaluation of sucrose supplementation effects on flowering time and molecular responses.

Main Results:

• Nitric oxide-induced late-flowering is independent of FNR1 and CRY1, unlike nitrogen-induced delay.
• High nitrogen decreased circadian clock transcript amplitudes, while NO differentially affected them, increasing some and decreasing others (CO, GI).
• Sucrose counteracted NO-induced flowering delay and reversed declines in CO and GI transcript amplitudes, also reducing NO-induced S-nitrosation on CO and GI proteins.

Conclusions:

• Nitrogen and nitric oxide regulate plant flowering through signaling pathways that overlap but are not identical.
• Nitric oxide directly modifies key flowering regulators like CO and GI via S-nitrosation, a mechanism not observed with high nitrogen.
• Sucrose can mitigate some effects of nitric oxide on flowering time and circadian gene expression, suggesting a role in metabolic signaling.