Nano-silver controls transcriptional regulation of ethylene- and senescence-associated genes during senescence in cut carnations

Flower senescence in three carnation cultivars (‘Koba Kabana,’ ‘Purple Sky,’ and ‘Lufa’) was associated with increased ethylene production in floral tissues (petals and gynoecia). Treatment with silver nanoparticles (NAg) significantly reduced ethylene production in petals and gynoecia and significantly delayed petal senescence compared with that in control (untreated) flowers, as indicated by higher relative fresh weight. Gene expression analyses performed on petals and gynoecia from initial flower opening through senescence indicated that the expression levels of ethylene biosynthesis genes (ACS1 and ACO1) and a petal senescence-related gene (CP1) were significantly higher in control flowers than in NAg-treated flowers. In contrast, the expression level of the petal senescence inhibitor gene CPi was more upregulated in NAg-treated flowers than in control flowers. The expression levels of EIL1/2, ERS2, and EBF1 were significantly higher in control flowers, in which ethylene was highly produced, than in NAg-treated flowers, whereas the expression levels of CTR1 and ETR1 were lower. This indicates that EIL1/2, ERS2, and EBF1 positively regulate and CTR1 and ETR1 negatively regulate the ethylene signal transduction pathway in carnations. In addition, NAg can inhibit the expression of these positive regulator genes in carnations. Therefore, this study suggests that NAg is helpful in significantly repressing ethylene production and delaying petal senescence in carnations via the suppression of ethylene biosynthesis genes, a petal senescence-related gene, and genes positively regulating ethylene signaling in petals and gynoecia.