title: Myrigalone A inhibits Lepidium sativum seed germination by interference with gibberellin metabolism and apoplastic superoxide production required for embryo extension growth and endosperm rupture.
abstract: Myrica gale L. (sweet gale) fruit leachate contains myrigalone A (MyA), a rare C-methylated dihydrochalcone and putative allelochemical, which is known to be a phytotoxin impeding seedling growth. We found that MyA inhibited Lepidium sativum L. seed germination in a dose-dependent manner. MyA did not affect testa rupture, but inhibited endosperm rupture and the transition to subsequent seedling growth. MyA inhibited micropylar endosperm cap (CAP) weakening and the increase in the growth potential of the radical/hypocotyl region (RAD) of the embryo, both being key processes required for endosperm rupture. We compared the contents of abscisic acid (ABA) and gibberellins in the tissues and found that the major bioactive forms of gibberellin in L. sativum seed tissues were GA(4) and GA(6), while GA(8) and GA(13) were abundant inactive metabolites. MyA did not appreciably affect the ABA contents, but severely interfered with gibberellin metabolism and signaling by inhibiting important steps catalyzed by GA3 oxidase, as well as by interfering with the GID1-type gibberellin signaling pathway. The hormonally and developmentally regulated formation of apoplastic superoxide radicals is important for embryo growth. Specific zones within the RAD were associated with accumulation of apoplastic superoxide radicals and endoreduplication indicative of embryo cell extension. MyA negatively affected both of these processes and acted as a scavenger of apoplastic reactive oxygen species. We propose that MyA is an allelochemical with a novel mode of action on seed germination.
authors: University of Freiburg, Faculty of Biology, Institute for Biology II, Botany/Plant Physiology, Freiburg, Germany. oracz.krystyna@op.pl
authors: Krystyna
authors: K
authors: Oracz
authors: Antje
authors: A
authors: Voegele
authors: Danuse
authors: D
authors: Tarkowská
authors: Dominique
authors: D
authors: Jacquemoud
authors: Veronika
authors: V
authors: Turecková
authors: Terezie
authors: T
authors: Urbanová
authors: Miroslav
authors: M
authors: Strnad
authors: Elwira
authors: E
authors: Sliwinska
authors: Gerhard
authors: G
authors: Leubner-Metzger
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology; D047188:Chalcones / Q000737:chemistry / Q000494:pharmacology*; D003512:Cyclohexanones / Q000737:chemistry / Q000494:pharmacology*; D056625:Endosperm / Q000187:drug effects / Q000196:embryology* / Q000235:genetics; D005030:Ethylenes / Q000494:pharmacology; D005638:Fruit / Q000187:drug effects / Q000378:metabolism; D020440:Gene Duplication / Q000187:drug effects / Q000235:genetics; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000187:drug effects* / Q000235:genetics; D005875:Gibberellins / Q000378:metabolism* / Q000494:pharmacology; D031220:Lepidium sativum / Q000187:drug effects* / Q000196:embryology* / Q000235:genetics / Q000378:metabolism; D009928:Organ Specificity / Q000187:drug effects / Q000235:genetics; D053147:Plant Exudates / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics / Q000254:growth & development; D013481:Superoxides / Q000378:metabolism*
chemical_list: D047188:Chalcones; D003512:Cyclohexanones; D005030:Ethylenes; D005875:Gibberellins; D053147:Plant Exudates; C571989:myrigalone A; D013481:Superoxides; D000040:Abscisic Acid; C036216:ethylene