Expression levels of ethylene biosynthetic genes and senescence-related genes in carnation (Dianthus caryophyllus L.) with ultra-long-life flowers

- Carnation line 532-6 has ultra-long flower life, 29 days without chemical treatment.
- Expression of senescence-related genes in line 532-6 was investigated.
- DcCP1 transcript levels differed in 532-6 and cultivars with shorter flower life.
- The time course of DcCPIn expression differed between 532-6 and these cultivars.

Carnation (Dianthus caryophyllus L.) line 532-6 has ultra-long flower life (29 days without chemical treatment). We investigated ethylene production and expression of ethylene biosynthetic genes and senescence-related genes in the flowers of 532-6 in comparison with those of a control cultivar, 'Francesco' and a cultivar with long flower life, 'Miracle Rouge' (MR). 'Francesco' flowers, but not those of MR and 532-6, showed typical symptoms of ethylene-dependent senescence. The flowers of MR and 532-6 produced very low levels of ethylene as a result of very low expression levels of two ethylene biosynthetic genes, DcACS1 and DcACO1. The expression of some senescence-related genes (DcbGal, DcGST1 and DcLip) increased in 'Francesco' petals by day 6, but remained low in the petals of MR and 532-6 throughout the experiment, whereas there was a small difference between the levels of the DcCP1 transcript in MR and 532-6. The expression of DcCPIn was regulated differently in all three cultivars. In 'Francesco' petals, the DcCPIn expression level sharply decreased on day 6 and 7; in MR, the DcCPIn level increased on day 7 and decreased by day 16, whereas in 532-6 it increased on day 3 and then gradually decreased until day 25. The results suggest that the extended flower life of MR and 532-6 in comparison with 'Francesco' depends on reduced levels of ethylene production, low levels of ethylene biosynthetic gene expression, and senescence-related gene expression; the difference between MR and 532-6 may be due, in particular, to DcCPIn and DcCP1.