title: High levels of jasmonic acid antagonize the biosynthesis of gibberellins and inhibit the growth of Nicotiana attenuata stems.
abstract: Hormones play pivotal roles in regulating plant development, growth, and stress responses, and cross-talk among different hormones fine-tunes various aspects of plant physiology. Jasmonic acid (JA) is important for plant defense against herbivores and necrotic fungi and also regulates flower development; in addition, Arabidopsis mutants over-producing JA usually have stunted stems and wound-induced jasmonates suppress Arabidopsis growth, suggesting that JA is also involved in stem elongation. Gibberellins (GAs) promote stem and leaf growth and modulate seed germination, flowering time, and the development of flowers, fruits, and seeds. However, little is known about the interaction between the JA and GA pathways. Two calcium-dependent protein kinases, CDPK4 and CDPK5, are important suppressors of JA accumulation in a wild tobacco species, Nicotiana attenuata. The stems of N. attenuata silenced in CDPK4 and CDPK5 (irCDPK4/5 plants) had dramatically increased levels of JA and exhibited stunted elongation and had very high contents of secondary metabolites. Genetic analysis indicated that the high JA levels in irCDPK4/5 stems accounted for the suppressed stem elongation and the accumulation of secondary metabolites. Supplementation of GA(3)  to irCDPK4/5 plants largely restored normal stem growth to wild-type levels. Measures of GA levels indicated that over-accumulation of JA in irCDPK4/5 stems inhibited the biosynthesis of GAs. Finally, we show that JA antagonizes GA biosynthesis by strongly inhibiting the transcript accumulation of GA20ox and possibly GA13ox, the key genes in GA production, demonstrating that high JA levels antagonize GA biosynthesis in stems.
authors.affiliation: Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Hans-Knöll-Strasse 8, D-07745, Jena, Germany.
authors.forename: Maria
authors.initials: M
authors.lastname: Heinrich
authors.forename: Christian
authors.initials: C
authors.lastname: Hettenhausen
authors.forename: Theo
authors.initials: T
authors.lastname: Lange
authors.forename: Hendrik
authors.initials: H
authors.lastname: Wünsche
authors.forename: Jingjing
authors.initials: J
authors.lastname: Fang
authors.forename: Ian T
authors.initials: IT
authors.lastname: Baldwin
authors.forename: Jianqiang
authors.initials: J
authors.lastname: Wu
mesh_terms: D000085:Acetates / Q000494:pharmacology*; D019412:Anatomy, Cross-Sectional; D003517:Cyclopentanes / Q000378:metabolism* / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D020868:Gene Silencing; D017343:Genes, Plant; D005816:Genetic Complementation Test; D005875:Gibberellins / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000494:pharmacology; D054883:Oxylipins / Q000378:metabolism* / Q000494:pharmacology*; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D018547:Plant Stems / Q000187:drug effects / Q000201:enzymology / Q000254:growth & development*; D054817:Pollination; D011401:Promoter Regions, Genetic; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D014026:Nicotiana / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000254:growth & development; D014158:Transcription, Genetic
chemical_list: D000085:Acetates; D003517:Cyclopentanes; D005875:Gibberellins; D054883:Oxylipins; D010937:Plant Growth Regulators; D010940:Plant Proteins; C011006:jasmonic acid; C072239:methyl jasmonate; D011494:Protein Kinases