DELLA-mediated cotyledon expansion breaks coat-imposed seed dormancy

Area of Science:

• Plant Biology
• Seed Physiology
• Molecular Genetics

Background:

• Seed dormancy is crucial for plant survival and maintaining soil seed banks.
• The balance between abscisic acid (ABA) and gibberellin (GA) is a well-established theory for dormancy control.
• The precise molecular mechanisms by which ABA and GA regulate dormancy in imbibed seeds are not fully understood.

Purpose of the Study:

• To investigate the role of DELLA proteins in seed dormancy and germination.
• To elucidate the mechanism of hormone signal integration in controlling seed dormancy.
• To establish a model for how environmental factors influence dormancy.

Main Methods:

• Analysis of DELLA mutants in Arabidopsis thaliana.
• Observation of seed germination and seedling development, focusing on cotyledon expansion and radicle emergence.
• Comparison of DELLA mutants with previously characterized seed-dormancy mutants.

Main Results:

• DELLA proteins are essential for maintaining seed dormancy.
• Cotyledon expansion precedes radicle emergence during germination, and its final size correlates with seed dormancy levels in DELLA mutants.
• Existing seed-dormancy mutants exhibit defects in cotyledon size control, consistent with their germination potential.

Conclusions:

• DELLA proteins integrate light, temperature, and hormone signals to regulate cotyledon expansion.
• DELLA-mediated cotyledon expansion prior to radicle emergence is a key mechanism for overcoming seed coat-imposed dormancy.
• This process underlies seed dormancy control in Arabidopsis.