RESPECTIVE EFFECTS OF HYPOXIA AND GLUMELLAE ON THE EXPRESSION OF GENES INVOLVED IN ABA METABOLISM AND SIGNALLING PATHWAYS IN BARLEY GRAIN

MENDIONDO, GUILLERMINA M.; LEYMARIE, JULIETTE; CORBINEAU, FRANCOISE; BENECH-ARNOLD ROBERTO L.

JOURNAL OF EXPERIMENTAL BOTANY

Oxford Journal

Lugar: Lancaster UK; Año: 2008

0022-0957

Dormancy in the barley grain is expressed at temperatures above 15°C and is mostly imposed by the glumellae which have been suggested to limit oxygen supply to the embryo. Previous results have shown that hypoxia imposed either artificially or by the glumellae to embryos from dormant grains, increases embryo sensitivity to ABA, and promotes the accumulation of ABA during the first hours after imbibition. The aim of the present work was to investigate at a molecular level whether the glumellae and/or hypoxia interfere with ABA metabolism and signalling pathway. Expression of candidate genes involved in ABA metabolism (HvNCED1, HvNCED2 and HvABA8OH) and signalling (HvABI5, HvVP1 and HvPKABA) was analysed in embryos isolated from  dormant and non dormant whole or de-hulled grains  incubated in air or in hypoxia. The presence of the glumellae enhances the expression of genes involved in ABA metabolism (i.e. HvNCED1 at 5 h after imbibition and HvABA8OH at 12 h after imbibition) and signalling (HvABI5, HvVP1) with respect to that observed in de-hulled grains incubated in air. These results suggest that, at least part of the observed physiological responses to the presence of the glumellae, are regulated at the level of gene expression.  However, hypoxia imposed to dormant de-hulled grains did not mimic the presence of the glumellae in terms of expression of candidate genes. These results show that, although hypoxia mimics the presence of the glumellae in terms of both dormancy maintenance and ABA accumulation and sensitivity, its effects operate through different mechanisms. Key words: barley, hypoxia, dormancy, abscisic acid, gene expression