Winter induction of the galactinol synthase gene is associated with endodormancy in chestnut trees

Abstract

From the start of autumn and throughout winter dormancy, starch stored in the stems and buds of woody plants is broken down into oligosaccharides, mainly raffinose family oligosaccharides (RFOs). Given that RFO synthesis protects plants against winter cold, the enzyme galactinol synthase (catalyzing the first step in RFO synthesis) could play an important role in this process. Here, we characterized a galactinol synthase gene (CsGolS1) in chestnut and examined its expression in relation to tree dormancy. In chestnut branches, CsGolS1 mRNA levels paralleled the induction and course of winter dormancy, starting to rise at the beginning of autumn and elevated levels persisting until the onset of spring. In addition, exposure of chestnut plantlets to 4 °C induced the expression of the CsGolS1 gene in the stems. However, the permanent induction of stem CsGolS1 during winter months, rather than being a direct response to the cold, was found to be associated with the endodormancy state. This observation points to transcriptional mechanisms controlling the maintenance of endodormancy.