Conserved MYC transcription factors play a key role in jasmonate signaling both in tomato and Arabidopsis.
Jasmonates (JA) are important regulators of plant defense responses that activate expression of many wound-induced genes including the tomato proteinase inhibitor II (pin2) and leucine aminopeptidase (LAP) genes. Elements required for JA induction of the LAP gene are all present in the -317 to -78 proximal promoter region. Using yeast one-hybrid screening, we have identified the bHLH-leu zipper JAMYC2 and JAMYC10 proteins, specifically recognizing a T/G-box AACGTG motif in this promoter fragment. Mutation of the G-box element decreases JA-responsive LAP promoter expression. Expression of JAMYC2 and JAMYC10 is induced by JA, with a kinetics that precedes that of the LAP or pin2 transcripts. JAMYC overexpression enhanced JA-induced expression of these defense genes in potato, but did not result in constitutive transcript accumulation. Using footprinting assays, an additional protected element was identified, located directly adjacent to the T/G-box motif. Mutation of this element abolishes JA response, showing that recognition of this duplicated element is also required for gene expression. Knockout mutants in the AtMYC2 homolog gene of Arabidopsis are insensitive to JA and exhibit a decreased activation of the JA-responsive genes AtVSP and JR1. Activation of the PDF1.2 and b-CHI, ethylene/JA-responsive genes, is, however, increased in these mutants. These results show that the JAMYC/AtMYC2 transcription factors function as members of a MYC-based regulatory system conserved in dicotyledonous plants with a key role in JA-induced defense gene activation.
Boter
Marta
M
Departament de Genètica Molecular, Institut de Biologia Molecular de Barcelona, CID-CSIC, 08034 Barcelona, Spain.
Ruíz-Rivero
Omar
O
Abdeen
Ashraf
A
Prat
Salomé
S
D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D022782:CCAAT-Enhancer-Binding Protein-beta / Q000235:genetics; D017124:Conserved Sequence; D003517:Cyclopentanes / Q000378:metabolism* / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D016350:Leucine Zippers; D018551:Solanum lycopersicum / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation; D054883:Oxylipins; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic; D016271:Proto-Oncogene Proteins c-myc / Q000378:metabolism; D015534:Trans-Activators / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation
D029681:Arabidopsis Proteins; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D022782:CCAAT-Enhancer-Binding Protein-beta; D003517:Cyclopentanes; D004268:DNA-Binding Proteins; D054883:Oxylipins; D010940:Plant Proteins; D016271:Proto-Oncogene Proteins c-myc; D015534:Trans-Activators; D014157:Transcription Factors; C473611:MYC2 protein, Arabidopsis; C117206:MYC7E protein, Zea mays; C117013:AT5G57090 protein, Arabidopsis; C011006:jasmonic acid