title: Gibberellin-to-abscisic acid balances govern development and differentiation of the nucellar projection of barley grains.
abstract: In cereal grains, the maternal nucellar projection (NP) constitutes the link to the filial organs, forming a transfer path for assimilates and signals towards the endosperm. At transition to the storage phase, the NP of barley (Hordeum vulgare) undergoes dynamic and regulated differentiation forming a characteristic pattern of proliferating, elongating, and disintegrating cells. Immunolocalization revealed that abscisic acid (ABA) is abundant in early non-elongated but not in differentiated NP cells. In the maternally affected shrunken-endosperm mutant seg8, NP cells did not elongate and ABA remained abundant. The amounts of the bioactive forms of gibberellins (GAs) as well as their biosynthetic precursors were strongly and transiently increased in wild-type caryopses during the transition and early storage phases. In seg8, this increase was delayed and less pronounced together with deregulated gene expression of specific ABA and GA biosynthetic genes. We concluded that differentiation of the barley NP is driven by a distinct and specific shift from lower to higher GA:ABA ratios and that the spatial-temporal change of GA:ABA balances is required to form the differentiation gradient, which is a prerequisite for ordered transfer processes through the NP. Deregulated ABA:GA balances in seg8 impair the differentiation of the NP and potentially compromise transfer of signals and assimilates, resulting in aberrant endosperm growth. These results highlight the impact of hormonal balances on the proper release of assimilates from maternal to filial organs and provide new insights into maternal effects on endosperm differentiation and growth of barley grains.
authors.affiliation: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany Leibniz-Institut für Pflanzenbiochemie, D-06120 Halle (Saale), Germany.
authors.forename: Diana
authors.initials: D
authors.lastname: Weier
authors.affiliation: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
authors.forename: Johannes
authors.initials: J
authors.lastname: Thiel
authors.affiliation: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
authors.forename: Stefan
authors.initials: S
authors.lastname: Kohl
authors.affiliation: Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Slechtitelu 11, CZ-78371, Olomouc, Czech Republic.
authors.forename: Danuše
authors.initials: D
authors.lastname: Tarkowská
authors.affiliation: Laboratory of Growth Regulators, Palacky University and Institute of Experimental Botany, Academy of Sciences of the Czech Republic, Slechtitelu 11, CZ-78371, Olomouc, Czech Republic.
authors.forename: Miroslav
authors.initials: M
authors.lastname: Strnad
authors.affiliation: Leibniz-Institut für Pflanzenbiochemie, D-06120 Halle (Saale), Germany * Present address: Humboldt-Universität zu Berlin, Faculty of Agriculture and Horticulture, D-14195 Berlin, Germany.
authors.forename: Sara
authors.initials: S
authors.lastname: Schaarschmidt
authors.affiliation: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany.
authors.forename: Winfriede
authors.initials: W
authors.lastname: Weschke
authors.affiliation: Leibniz-Institut für Pflanzengenetik und Kulturpflanzenforschung, D-06466 Gatersleben, Germany weber@ipk-gatersleben.de.
authors.forename: Hans
authors.initials: H
authors.lastname: Weber
authors.affiliation: Leibniz-Institut für Pflanzenbiochemie, D-06120 Halle (Saale), Germany.
authors.forename: Bettina
authors.initials: B
authors.lastname: Hause
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism*; D002454:Cell Differentiation / Q000502:physiology; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005875:Gibberellins / Q000378:metabolism*; D001467:Hordeum / Q000378:metabolism*
chemical_list: D005875:Gibberellins; D000040:Abscisic Acid
keywords: Assimilate transfer; barley endosperm; gibberellin-to-abscisic acid balances; maternal–filial communication; nucellar projection; seg8 barley mutant.