Isolation and characterisation of senescence-related genes in carnations.

Thesis (M.Sc.)-University of Natal, Pietermaritzburg, 1995.

Senescence has been the subject of many studies, with the ultimate goal of increasing longevity of cut flowers, and for insight into the process of ageing. Senescence in the carnation is a complex phenomonen involving many physiological and molecular events. The carnation serves as an excellent subject for studies in senescence because of the clearly visible evidence of "in-rolling" of petals indicating the onset of senescence. Senescence in the carnation results in a large number of physiological changes in the flower which in many cases involve the action of the growth regulating hormones, particularly ethylene. Physiological studies of senescence, though exhaustive, have not as yet been able to pinpoint the source of control of senescence in the carnation and the exact controlling mechanism. Senescence has in the past been shown to be partially regulated at the transcriptional level, thus warranting studies in the area of molecular biology. The aim of the present investigation was to isolate genes active during senescence . To achieve this, mRNA from presenescent and senescing carnation petals, receptacles and ovaries was extracted. The mRNA was used to synthesise cDNA which was cloned into ۸gt10 phage to produce presenescent and senescing cDNA libraries of carnation material. The production of the petal library was the only library that, after boosting levels of petal cDNA using PCR (polymerase chain reaction) technology; was generated successfully. A subtraction procedure was carried out between the presenescent and senescing libraries to isolate the sequences unique to the senescing library ie. the genes active only during senescence. One sequence of 1 kb in size was isolated. This gene could be used for future research into the influence of the growth regulators on its activity, and also to pinpoint organs other than the petals where this particular gene is active. It would be of interest to investigate the sequence of the gene, for a comparison with other gene isolates in order to elucidate the identity and function of the gene product.