Awake1, an ABC-Type Transporter, Reveals an Essential Role for Suberin in the Control of Seed Dormancy.

Fabio Fedi,Steven Penfield,Christophe Bailly,Guillaume Menard,Carmel M O’Neill,Martin Trick,Peter J Eastmond,Simone Dechirico,Françoise Corbineau

doi:10.1104/pp.16.01556

Abstract

The mother plant plays an important dynamic role in the control of dormancy of her progeny seed in response to environmental signals. In order to further understand the mechanisms by which this dormancy control takes place in Arabidopsis (Arabidopsis thaliana), we conducted a forward genetic screen to isolate mutants that fail to enter dormancy in response to variation in temperature during seed set. We show that, for the first of these mutants, designated awake1, the maternal allele is required for entry into strongly dormant states and that awake1 mutants show seed phenotypes shown previously to be associated with the loss of suberin in the seed. We identify awake1 as an allele of ABCG20, an ATP-binding cassette transporter-encoding gene required for the transport of fatty acids during suberin deposition, and show that further suberin-deficient mutants have seed dormancy defects. Seed coat suberin composition is affected by temperature during seed maturation, but this response appears to be independent of ABCG20. We conclude that seed coat suberin is essential for seed dormancy imposition by low temperature and that the exclusion of oxygen and water from the seed by the suberin and tannin layers is important for dormancy imposition.

Highlights

The mother plant plays an important dynamic role in the control of dormancy of her progeny seed in response to environmental signals
Because we previously found that temperature affects seed dormancy, seed coat permeability, and seed coat tannin synthesis (MacGregor et al, 2015), and because temperature has been shown to affect suberin deposition in potato (Solanum tuberosum; Dean, 1989), we tested whether variation in the seed maturation temperature affected aliphatic monomer composition in the wild type and awe1-1
We found that all three abcg20 alleles shared a lower dormancy than the wild type, confirming that ABCG transporter 20 (ABCG20) is necessary for normal seed dormancy in Arabidopsis

Summary

Introduction

The mother plant plays an important dynamic role in the control of dormancy of her progeny seed in response to environmental signals. The mother plant plays an important role in this signaling process, collecting signals throughout her life history and modulating dormancy by providing hormones to maturing seeds and by plastic development of the tissues surrounding the embryo (Gutterman, 1978, 2000; Chen et al, 2014) This process is especially important in seeds with physiological dormancy that is coat imposed, which requires the presence and activity of the seed coat and endosperm structures that form a barrier between the embryo and the external environment (Debeaujon et al, 2000; Penfield et al, 2006b; Lee et al, 2010). Analysis and cloning of the first of these, awake (awe1), reveals an important role for seed coat suberin and maternal tissues in the imposition of maintenance of these more dormant states

Methods

Results

Conclusion