Abstract
Seed ageing is a major problem in the conservation of germplasm resources. The involvement of possible signalling molecules during seed deterioration needs to be identified. In this study, we confirmed that nitric oxide (NO), a key signalling molecule in plants, plays a positive role in the resistance of elm seeds to deterioration. To explore which metabolic pathways were affected by NO, an untargeted metabolomic analysis was conducted, and 163 metabolites could respond to both NO and the ageing treatment. The primary altered pathways include glutathione, methionine, and carbohydrate metabolism. The genes involved in glutathione and methionine metabolism were up-regulated by NO at the transcriptional level. Using a biotin switch method, proteins with an NO-dependent post-translational modification were screened during seed deterioration, and 82 putative S-nitrosylated proteins were identified. Eleven of these proteins were involved in carbohydrate metabolism, and the activities of the three enzymes were regulated by NO. In combination, the results of the metabolomic and S-nitrosoproteomic studies demonstrated that NO could activate glycolysis and inhibit the pentose phosphate pathway. In summary, the combination of these results demonstrated that NO could modulate carbohydrate metabolism at the post-translational level and regulate glutathione and methionine metabolism at the transcriptional level. It provides initial insights into the regulatory mechanisms of NO in seed deterioration.
Highlights
Seed ageing is an irreversible process of the gradual decline of seed vigour
When the elm seeds were exposed to vapours from an nitric oxide (NO) donor sodium nitroprusside (SNP), the germination percentage of the ageing seeds was affected (Fig. 1A).The germination percentage was enhanced with a moderate concentration of SNP (100 μM) from 51% to 65% after 3 d of controlled deterioration treatment (CDT), and it even increased from 2% to 18% after 5 d of CDT
Lower (50 μM) or higher (150 μM) concentrations of SNP had no effect on the vigour of the aged seeds, showing a narrow window of SNP concentration in the resistance to seed ageing (Supplementary Fig. S1).To confirm further the role of NO in seed ageing, elm seeds pre-treated with the NO scavenger c-PTIO and/or SNP were subjected to CDT, after which the seed vigor was determined (Fig. 1B)
Summary
Seed ageing is an irreversible process of the gradual decline of seed vigour. It is characterized as a reduction of antioxidant systems, the disruption of cellular membranes, the damage of genetic integrity, the peroxidation of lipids, and the degradation of proteins in seeds. Recent studies found that the typical features of programmed cell death (PCD), such as DNA fragmentation, a TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labelling)-positive nucleus, cytochrome c release, and. In the Arabidopsis mutant noa with a defective nitric oxide associated 1 gene, the detached leaves and intact plants senesced more rapidly than the wild type, and treatment with the NO donor sodium nitroprusside (SNP) slowed the dark-induced senescence of the noa mutant leaves (Guo and Crawford, 2005). Its exact role in seed deterioration has not been investigated
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