Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE credits
Dehydrins are proteins formed in plants in connection to different kinds of stress, such as cold and drought, and dehydrin gene expression can be used as a marker of freezing hardiness. It would be useful if the dehydrin content in young plants could be influenced by chemical treatment, which could simplify the inwintering process for conifer seedlings in plant nurseries. The effect of seed treatment with nicotinamide on the expression of the dehydrin 5 gene (Psdhn5) in Pinus sylvestris was studied.
Approximately 20% of the seeds in the batch of seeds used for this study were light coloured seeds and the rest dark brown or black. A potential connection between seed colour and gene expression was investigated. Psdhn5 expression was analyzed in seeds and in roots of one month old seedlings. Seeds were analyzed both directly after four hours of treatment with 2,5 mM nicotinamide or water (control), and after air drying over night. The Psdhn5 expression in control seeds, not dried over night, was approximately the same in light and dark coloured seeds. Nicotinamide treatment of seeds resulted in decreased Psdhn5 expression in seeds of both colours. In rotts from darj coloured seeds the expression was lower if seeds had been treated with nicotinamide, but also if the seeds had been left drying over night. However, in roots from light coloured seeds there was only a small decrease in expression after seed drying and only a small, if any, decrease after nicotinamide seed treatment. Compared to dark coloured seeds, the light coloured ones were slower to germinate, but was stimulated by nicotinamide treatment.
Overall, the results indicate a way to influence dehydrin expression in young pine seedlings by a simple seed treatment with a natural non-toxic compound. This knowledge may be useful in controlling the inwintering process for cold storage of seedlings in plant nurseries. The study also illustrates the impact of different phenotypes among pine seeds, which can be of importance in the production of healthy and stress tolerant seedlings within forestry. Furthermore, this study also points at sensitivity of gene expression in the growing plant regarding treatment and general environmental factos at the seed stage.