Scientific review explains how seeds break dormancy

During germination, seeds face biomechanical and molecular challenges to initiate embryo growth. A recent study by researcher Angel J. Matilla, from the University of Santiago de Compostela, gathered evidence detailing how this process depends on interactions between hormones, internal pressure, and cell wall (CW) modifications.

Endosperm expansion pressure is the driving force behind seed coat rupture and radicle protrusion. This force results from water absorption and cell wall loosening, especially in the micropyle region. Expansins (EXPs), mannanases (MANs) and transglycosylases (XTHs) are the main agents involved.

These enzymes promote the relaxation of CWs, reducing the mechanical resistance of the seed coat. In the model Arabidopsis thaliana, the expansin AtEXP2, activated by regulators NAC25/NAC1L and the hormone gibberellin (GA), is crucial for endosperm cell expansion. Mutants defective in this gene show delayed germination.

The study also highlights the importance of microtubules in directing cell expansion. These structures align cellulose microfibrils, guiding cell growth. The formation of these microtubules, from the synthesis of beta-tubulin, is inhibited by abscisic acid (ABA), reinforcing their inhibitory role in germination.

Another aspect is the role of the endosperm as an environmental sensor. It responds to external and internal signals, such as light and hormones, and releases enzymes that facilitate the rupture of the CW. The presence of the endospermic cuticle, associated with tannins and regulated by GSO1/GSO2 kinases, also modulates permeability and protects the embryo.

In the agricultural context, understanding these mechanisms allows advances in genetic improvement and seed biotechnology. Genes such as AtMAN5 and LeMAN2, associated with the degradation of mannose polymers, become targets to increase vigor and uniformity in seedling emergence.

Furthermore, epigenetic factors such as histone methylations and acetylations modulate the expression of key genes such as DOG1 and ABI5, which regulate dormancy and the transition to active growth.

More information at doi.org/10.1016/j.plantsci.2025.112612