title: A role for arabinogalactan proteins in gibberellin-induced alpha-amylase production in barley aleurone cells.
abstract: Arabinogalactan proteins (AGPs) are plant proteoglycans that have been implicated in plant growth and development. The possible involvement of AGPs in the action of gibberellin (GA), a class of plant hormones, was examined by applying beta-glucosyl Yariv reagent (beta-Glc)3Y, a synthetic phenyl glycoside that interacts selectively with AGPs, to barley aleurone protoplasts. Gibberellin induces transcription and secretion of alpha-amylases in the protoplasts. Induction of alpha-amylase was clearly inhibited by (beta-Glc)3Y but not by (alpha-Gal)3Y, a negative control of the Yariv reagent that does not interact with AGPs. Transfection analysis, using an alpha-amylase promoter-GUS fusion gene in the protoplasts, indicated that the transcriptional activation of the alpha-amylase promoter was inhibited specifically by (beta-Glc)3Y. These observations are the first indication of an involvement of AGPs in a plant hormone function. The inhibitory effect of (beta-Glc)3Y was not observed when aleurone layers or half-seed grains were used. This result, together with the fact that protoplasts do not have cell walls, suggests that the AGPs that function in alpha-amylase induction reside at the plasma membrane. An aleurone-specific AGP was detected by reversed-phase HPLC, and supported the idea that an AGP may play an important role in aleurone-specific events. The possible mechanism of AGP function in gibberellin-induced alpha-amylase production is discussed.
authors.affiliation: Department of Applied Biological Chemistry, The University of Tokyo, Japan. ayoshi@pgr1.ch.a.u-tokyo.ac.jp
authors.forename: Yoshihito
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Mamiko
authors.initials: M
authors.lastname: Kitagawa
authors.forename: J Paul
authors.initials: JP
authors.lastname: Knox
authors.forename: Isomaro
authors.initials: I
authors.lastname: Yamaguchi
mesh_terms: D002470:Cell Survival / Q000187:drug effects; D002473:Cell Wall / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D004790:Enzyme Induction / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005875:Gibberellins / Q000494:pharmacology*; D005960:Glucosides / Q000494:pharmacology; D005966:Glucuronidase / Q000235:genetics / Q000378:metabolism; D001467:Hordeum / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009088:Mucoproteins / Q000502:physiology*; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000494:pharmacology; D010937:Plant Growth Regulators / Q000494:pharmacology; D010940:Plant Proteins; D011401:Promoter Regions, Genetic / Q000235:genetics; D011523:Protoplasts / Q000187:drug effects / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012639:Seeds / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D014162:Transfection; D000516:alpha-Amylases / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D004791:Enzyme Inhibitors; D005875:Gibberellins; D005960:Glucosides; D009088:Mucoproteins; D010937:Plant Growth Regulators; D010940:Plant Proteins; D011993:Recombinant Fusion Proteins; C104977:Yariv reagent; C006619:arabinogalactan proteins; D010696:Phloroglucinol; D000516:alpha-Amylases; D005966:Glucuronidase