title: Transcriptional down-regulation by abscisic acid of pathogenesis-related beta-1,3-glucanase genes in tobacco cell cultures.
abstract: Class I isoforms of beta-1,3-glucanases (betaGLU I) and chitinases (CHN I) are antifungal, vacuolar proteins implicated in plant defense. Tobacco (Nicotiana tabacum L.) betaGLU I and CHN I usually exhibit tightly coordinated developmental, hormonal, and pathogenesis-related regulation. Both enzymes are induced in cultured cells and tissues of cultivar Havana 425 tobacco by ethylene and are down-regulated by combinations of the growth hormones auxin and cytokinin. We report a novel pattern of betaGLU I and CHN I regulation in cultivar Havana 425 tobacco pith-cell suspensions and cultured leaf explants. Abscisic acid (ABA) at a concentration of 10 micron markedly inhibited the induction of betaGLU I but not of CHN I. RNA-blot hybridization and immunoblot analysis showed that only class I isoforms of betaGLU and CHN are induced in cell culture and that ABA inhibits steady-state betaGLU I mRNA accumulation. Comparable inhibition of beta-glucuronidase expression by ABA was observed for cells transformed with a tobacco betaGLU I gene promoter/beta-glucuronidase reporter gene fusion. Taken together, the results strongly suggest that ABA down-regulates transcription of betaGLU I genes. This raises the possibility that some of the ABA effects on plant-defense responses might involve betaGLU I.
authors.affiliation: Friedrich Miescher Institute, Basel, Switzerland.
authors.forename: E
authors.initials: E
authors.lastname: Rezzonico
authors.forename: N
authors.initials: N
authors.lastname: Flury
authors.forename: F
authors.initials: F
authors.lastname: Meins
authors.forename: R
authors.initials: R
authors.lastname: Beffa
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D001483:Base Sequence; D002478:Cells, Cultured; D002688:Chitinases / Q000096:biosynthesis*; D017931:DNA Primers; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D043326:Glucan 1,3-beta-Glucosidase; D007700:Kinetics; D010947:Plants, Toxic; D016133:Polymerase Chain Reaction; D014026:Nicotiana / Q000201:enzymology* / Q000235:genetics; D014158:Transcription, Genetic / Q000187:drug effects*; D001617:beta-Glucosidase / Q000096:biosynthesis*
chemical_list: D017931:DNA Primers; D000040:Abscisic Acid; D002688:Chitinases; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase