Transcriptional down-regulation by abscisic acid of pathogenesis-related beta-1,3-glucanase genes in tobacco cell cultures.
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.
Rezzonico
E
E
Friedrich Miescher Institute, Basel, Switzerland.
Flury
N
N
Meins
F
F
Beffa
R
R
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*
D017931:DNA Primers; D000040:Abscisic Acid; D002688:Chitinases; D001617:beta-Glucosidase; D043326:Glucan 1,3-beta-Glucosidase