Effect of cytokinins on delaying petunia flower senescence: a transcriptome study approach

Flower senescence is a fascinating natural process that represents the final developmental stage in the life of a flower. Plant hormones play an important role in regulating the timing of flower senescence. Ethylene is a trigger and usually accelerates the senescence rate, while cytokinins are known to delay it. The aim of this work was to study the effect of 6-benzylaminopurine (BA) on petal senescence by transcript profile comparison after 3 or 6 h using a cross-species method by hybridizing petunia samples to a 4 x 44 K Agilent tomato array. The relative content of ethylene, abscisic acid, anthocyanins, total carotenoids and total phenols that determine the physiological behaviours of the petal tissue were measured. BA treatment prolonged the flower life and increased the concentrations of phenols and anthocyanins, while total carotenoids did not increase and were lower than the control. The ethylene biosynthetic and perception gene expressions were studied immediately after treatment until 24 h and all genes were repressed, while ethylene production was strongly induced after 4 days. The microarray analyses highlighted that BA strongly affected gene regulation after 3 h, but only 14 % of genes remained differentially expressed after 6 h. The most affected pathways and genes were those related to stress, such as heat shock proteins, abscisic acid (ABA) catabolism and its signalling pathway, lipid metabolism and antioxidant defence systems. A gene annotation enrichment analysis using DAVID showed that the most important gene clusters were involved in energy generation and conservation processes. In addition to the ethylene pathway, cytokinins seem to be strongly involved the regulation of the ABA response in flower tissues.