Nitro-fatty acids modulate germination onset through S-nitrosothiol metabolism

Nitro-fatty acids (NO2-FAs) have emerged as key components of nitric oxide (NO) signaling in eukaryotes. We previously described how nitro-linolenic acid (NO2-Ln), the major NO2-FA detected in plants, regulates S-nitrosoglutathione (GSNO) levels in Arabidopsis (Arabidopsis thaliana). However, the underlying molecular mechanisms remain undefined. Here, we used a combination of physiological, biochemical, and molecular approaches to provide evidence that NO2-Ln modulates S-nitrosothiol (SNO) content through S-nitrosylation of S-nitrosoglutathione reductase1 (GSNOR1) and its impact on germination onset. The aer mutant (a knockout mutant of the alkenal reductase enzyme; AER) exhibits higher NO2-Ln content and lower GSNOR1 transcript levels, reflected by higher SNO content and S-nitrosylated proteins. Given its capacity to release NO, NO2-Ln mediates the S-nitrosylation of GSNOR1, demonstrating that NO2-FAs can indirectly modulate total SNO content in plants. Moreover, the ectopic application of NO2-Ln to dormant seeds enhances germination success similarly to the aer germination rate, which is mediated by the degradation of master regulator ABSCISIC ACID INSENSITIVE 5 (ABI5). Our results establish that NO2-FAs regulate plant development through NO and SNO metabolism and reveal a role of NO2-FAs in plant physiology.