DELLA-mediated cotyledon expansion breaks coat-imposed seed dormancy

TY - JOUR

T1 - DELLA-mediated cotyledon expansion breaks coat-imposed seed dormancy

AU - Penfield, S.

AU - Gilday, A.D.

AU - Halliday, K.J.

AU - Graham, I.A.

PY - 2006/12/5

Y1 - 2006/12/5

N2 - Seed dormancy is a key adaptive trait in plants responsible for the soil seed bank. The long established hormone-balance theory describes the antagonistic roles of the dormancy promoting plant hormone abscisic acid (ABA), and the germination promoting hormone gibberellin (GA) in dormancy control [1], [2], [3], [4], [5] and [6]. Light, temperature, and other dormancy-breaking signals function to modulate the synthesis and perception of these hormones in the seed [7], [8], [9] and [10]. However, the way in which these hormones control dormancy in the imbibed seed remains unknown. Here, we show that the DELLA protein regulators of the GA response are required for dormancy and describe a model through which hormone signal integration and dormancy regulation is achieved. We demonstrate that cotyledon expansion precedes radicle emergence during Arabidopsis seed germination and that a striking correlation exists between final seedling cotyledon size and seed dormancy in the DELLA mutants. Furthermore, twelve previously characterized seed-dormancy mutants are also defective in the control of cotyledon size in a manner consistent with their effect on germination potential. We propose that DELLA-mediated, light-, temperature-, and hormone-responsive cotyledon expansion prior to radicle emergence overcomes dormancy imposed by the seed coat and underlies seed-dormancy control in Arabidopsis.

AB - Seed dormancy is a key adaptive trait in plants responsible for the soil seed bank. The long established hormone-balance theory describes the antagonistic roles of the dormancy promoting plant hormone abscisic acid (ABA), and the germination promoting hormone gibberellin (GA) in dormancy control [1], [2], [3], [4], [5] and [6]. Light, temperature, and other dormancy-breaking signals function to modulate the synthesis and perception of these hormones in the seed [7], [8], [9] and [10]. However, the way in which these hormones control dormancy in the imbibed seed remains unknown. Here, we show that the DELLA protein regulators of the GA response are required for dormancy and describe a model through which hormone signal integration and dormancy regulation is achieved. We demonstrate that cotyledon expansion precedes radicle emergence during Arabidopsis seed germination and that a striking correlation exists between final seedling cotyledon size and seed dormancy in the DELLA mutants. Furthermore, twelve previously characterized seed-dormancy mutants are also defective in the control of cotyledon size in a manner consistent with their effect on germination potential. We propose that DELLA-mediated, light-, temperature-, and hormone-responsive cotyledon expansion prior to radicle emergence overcomes dormancy imposed by the seed coat and underlies seed-dormancy control in Arabidopsis.

U2 - 10.1016/j.cub.2006.10.057

DO - 10.1016/j.cub.2006.10.057

M3 - Article

SN - 0960-9822

VL - 16

SP - 2366

EP - 2370

JO - Current Biology

JF - Current Biology

IS - 23

ER -