Fragaria ananassa DAM4 expression correlates with vegetative growth during semi-dormancy breaking

Dormancy-Associated MADS-BOX (DAM)3 and DAM4 have been described as potential regulators of winter dormancy in cultivated strawberry (Fragaria x ananassa Duch.). These genes are upregulated under short-day conditions and downregulated under chilling conditions. The aim of the current work is to test the hypothesis that the expression of DAM3 and DAM4 correlates negatively with vegetative growth during dormancy induction and breaking. The expression of DAM3 and DAM4 as well as plant morphology and physiology was analyzed during a period of semi-dormancy induction and breaking. Furthermore, DAM3 and DAM4 expression was compared between cultivars with different chill requirements. Lastly, the DAM1, DAM2, DAM3, and DAM4 expression of concurrently growing summer and winter leaves was compared at multiple stages of dormancy breaking. DAM3 and DAM4 expression negatively correlated with leaf area and petiole length. We conclude that DAM3 and DAM4 expression patterns are consistent with that of regulators of semi-dormancy. DAM4 expression in particular correlates strongly with vegetative growth during semi-dormancy breaking. DAM3 or DAM4 expression was not found to correlate with the cultivar-specific chill requirements. Lastly, no relevant differences in DAM expression were found between summer and winter leaves.