Functional characterization of Dormancy-Associated MADS-Box genes in apple

The cultivated apple Malus ×domestica Borkh. is grown globally, but climate change is disrupting production, particularly by altering flower bud dormancy.
Warmer temperatures during winter months cause earlier bud break and flowering, increasing susceptibility to late frost events. Dormancy-Associated MADS-Box (DAM) genes are linked to dormancy regulation in deciduous fruit trees, including apple, though their specific roles remain unclear.
Several DAM genes were identified on different chromosomes in the apple genome sequence.
Their expression patterns were analyzed in buds of different apple cultivars during the dormant phase in the winter months.
To explore their function, apple trees were genetically modified to overexpress or silence MdDAM1 and MdDAM4. Phenotypic and transcriptomic analyses confirmed that both genes are essential for dormancy regulation.
Trees lacking functional MdDAM1 or MdDAM4 genes failed to enter dormancy.
To avoid off-target effects from RNAi silencing, CRISPR/Cas-mediated genome editing was also used to edit MdDAM1 in the apple cultivar ‘Gala’. Of 732 regenerated shoot lines, 60 showed mutations.
None of these lines had both alleles of MdDAM1 mutated.
A second regeneration step yielded 17 lines with uniform biallelic MdDAM1 mutations, which are currently under investigation.

International Symposium on Biotechnological Tools in Horticulture

J. Lempe, S. Schröpfer, L. Baader, M. Moser, E. Asquini, A. Si-Ammour, H. Flachowsky

dormancy, DAM gene, Malus × domestica, growth cessation, transgenic apple, genome editing

https://doi.org/10.17660/ActaHortic.2026.1454.33