title: Inhibition of germination of dormant barley (Hordeum vulgare L.) grains by blue light as related to oxygen and hormonal regulation.
abstract: Germination of primary dormant barley grains is promoted by darkness and temperatures below 20 °C, but is strongly inhibited by blue light. Exposure under blue light at 10 °C for periods longer than five days, results in a progressive inability to germinate in the dark, considered as secondary dormancy. We demonstrate that the inhibitory effect of blue light is reinforced in hypoxia. The inhibitory effect of blue light is associated with an increase in embryo abscisic acid (ABA) content (by 3.5- to 3.8-fold) and embryo sensitivity to both ABA and hypoxia. Analysis of expression of ABA metabolism genes shows that increase in ABA mainly results in a strong increase in HvNCED1 and HvNCED2 expression, and a slight decrease in HvABA8'OH-1. Among the gibberellins (GA) metabolism genes examined, blue light decreases the expression of HvGA3ox2, involved in GA synthesis, increases that of GA2ox3 and GA2ox5, involved in GA catabolism, and reduces the GA signalling evaluated by the HvExpA11 expression. Expression of secondary dormancy is associated with maintenance of high embryo ABA content and a low HvExpA11 expression. The partial reversion of the inhibitory effect of blue light by green light also suggests that cryptochrome might be involved in this hormonal regulation.
authors.affiliation: UR5-EAC 7180 CNRS, PCMP, UPMC Univ Paris 06, Boîte courrier 156, Bat C, 4 place Jussieu, F-75005, Paris, France.
authors.forename: Hai Ha
authors.initials: HH
authors.lastname: Hoang
authors.forename: Julien
authors.initials: J
authors.lastname: Sechet
authors.forename: Christophe
authors.initials: C
authors.lastname: Bailly
authors.forename: Juliette
authors.initials: J
authors.lastname: Leymarie
authors.forename: Françoise
authors.initials: F
authors.lastname: Corbineau
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D018525:Germination / Q000528:radiation effects*; D005875:Gibberellins / Q000378:metabolism; D001467:Hordeum / Q000254:growth & development / Q000378:metabolism / Q000528:radiation effects*; D010100:Oxygen / Q000378:metabolism*; D010937:Plant Growth Regulators / Q000378:metabolism*; D012639:Seeds / Q000254:growth & development / Q000528:radiation effects; D015398:Signal Transduction; D013696:Temperature
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C007842:gibberellic acid; D010100:Oxygen
keywords: abscisic acid (ABA); gibberellins (GA); primary dormancy; secondary dormancy