Nitric oxide and S-nitrosoglutathione function additively during plant immunity

Area of Science:

• Plant molecular biology
• Plant pathology
• Redox signaling

Background:

• Nitric oxide (NO) is a vital regulator of plant cellular processes.
• S-nitrosylation, mediated by S-nitrosoglutathione reductase 1 (GSNOR1), is a key NO bioactivity transfer pathway.
• Dysregulation of S-nitrosylation occurs when GSNOR1 function is absent, leading to GSNO accumulation.

Purpose of the Study:

• To investigate the role of endogenous nitric oxide (NO) accumulation in plant immunity.
• To elucidate the relationship between NO, S-nitrosoglutathione (GSNO), and plant defense mechanisms.
• To determine the functional relationship between NO and GSNOR1 in Arabidopsis.

Main Methods:

• Utilized Arabidopsis loss-of-function mutants in NO Overexpression 1 (NOX1) to induce NO accumulation.
• Assessed plant resistance against pathogens and analyzed salicylic acid (SA) synthesis and signaling pathways.
• Employed GSNOR1 transgene complementation and generated double mutants (atgsnor1-3 nox1-1) to study gene functions.

Main Results:

• NO accumulation in nox1 mutants compromised Resistance (R) gene-mediated protection, basal resistance, and defense against pathogens.
• SA synthesis and signaling were suppressed in nox1 plants, reducing SA-dependent defense gene expression.
• GSNOR1 expression rescued SNO-dependent phenotypes but not NO-related traits in nox1 mutants, and double mutants showed increased bacterial titers.

Conclusions:

• Endogenous NO accumulation disrupts plant immunity by suppressing SA-mediated defenses.
• GSNO and NO function additively, potentially targeting distinct or overlapping molecular pathways in plant immunity and development.
• GSNOR1 plays a critical role in regulating NO homeostasis and plant defense responses.