Expression of abscisic and gibberellic acid signalling factors in Fagus sylvatica L. seeds during dormancy breaking and germination

Abstract

European beech seeds are characterised by deep physiological dormancy and to germinate, they require several weeks of stratification at 3°C. Seed dormancy is under hormonal regulation, but the details of how hormones regulate deep dormancy in trees remain not yet well elucidated. We hypothesised that the mechanism of seed dormancy breaking is differentially regulated according to depth of dormancy. Expression of ABI5 and 14-3-3, members of the abscisic acid pathway, and RGL2, a member of gibberellic acid pathways, were examined at the protein and mRNA levels during dormancy alleviation of beech seeds. Unlike in non-deep dormant seeds, ABI5, 14-3-3 and RGL2 were present during nearly all periods of cold stratification in beech seeds, but during dormancy breaking and germination these proteins nearly disappeared. Relative abundances of ABI5 and 14-3-3 transcripts were the highest in dormant dry seeds, and during stratification it decreased gradually. We suppose that during stratification, de novo translation of proteins on the basis of deposited mRNA occurred. On the base of our research we can conclude that the seed dormancy breaking mechanism differs according to seed’s dormancy depth.