Sucrose plays crucial roles in growth and responses of plants to the environment, including those in ornamental species. During post-harvest handling of cut flowers,
sucrose degradation is an essential process of inter- and intra-cellular
carbon partitioning affecting flower opening and senescence and, subsequently, flower quality. However, complete information about the molecular basis of
sucrose degradation in ornamental flowers, which can be catalyzed by two kinds of sucrolytic
enzymes,
invertase (INV), and
sucrose synthase (SUS), is not available from past reports. The present study shows that
sucrose treatment of carnation (Dianthus caryophyllus L.) florets increased
starch content in petals, accompanied by decreased vacuolar INV (VIN) activity and increased SUS activity. However, hypoxic treatment of carnation florets decreased
sucrose content and cell-wall INV (CWIN) activity in petals. In silico analysis using the carnation genome database identified six CWIN, three VIN, eight cytoplasmic INV (CIN), and five SUS genes. Real-time RT-PCR analysis confirmed that these genes are differentially expressed in carnation petals in response to
sucrose and hypoxic treatments, partially corresponding to the changes in
enzyme activities. In contrast to DcSUS1 (Dca4507.1), a SUS gene already reported in carnation, which showed preferential expression under aerated conditions, the expression of DcSUS2 (Dca22218.1), an undescribed carnation SUS gene, was enhanced under
hypoxia similarly to an
alcohol dehydrogenase gene DcADH1 (Dca18671.1). These results suggest that
sugar metabolism in carnation petals is regulated in response to environmental cues, accompanied by modulated activities and gene expression of a set of sucrolytic
enzymes.