title: The Mediator Complex Subunits MED14, MED15, and MED16 Are Involved in Defense Signaling Crosstalk inArabidopsis.
abstract: Mediator is a highly conserved protein complex that functions as a transcriptional coactivator in RNA polymerase II (RNAPII)-mediated transcription. TheArabidopsisMediator complex has recently been implicated in plant immune responses. Here, we compared salicylic acid (SA)-, methyl jasmonate (MeJA)-, and the ethylene (ET) precursor 1-aminocyclopropane-1-carboxylic acid (ACC)-induced defense and/or wound-responsive gene expression in 14ArabidopsisMediator subunit mutants. Our results show that MED14, MED15, and MED16 are required for SA-activated expression of the defense marker genePATHOEGNESIS-RELATED GENE1, MED25 is required for MeJA-induced expression of the wound-responsive marker geneVEGATATIVE STORAGE PROTEIN1(VSP1), MED8, MED14, MED15, MED16, MED18, MED20a, MED25, MED31, and MED33A/B (MED33a and MED33B) are required for MeJA-induced expression of the defense maker genePLANT DEFENSIN1.2(PDF1.2), and MED8, MED14, MED15, MED16, MED25, and MED33A/B are also required for ACC-triggered expression ofPDF1.2. Furthermore, we investigated the involvement of MED14, MED15, and MED16 in plant defense signaling crosstalk and found that MED14, MED15, and MED16 are required for SA- and ET-mediated suppression of MeJA-inducedVSP1expression. This result suggests that MED14, MED15, and MED16 not only relay defense signaling from the SA and JA/ET defense pathways to the RNAPII transcription machinery, but also fine-tune defense signaling crosstalk. Finally, we show that MED33A/B contributes to the necrotrophic fungal pathogenBotrytis cinerea-induced expression of the defense genesPDF1.2, HEVEIN-LIKE, andBASIC CHITINASEand is required for full-scale basal resistance toB. cinerea, demonstrating a positive role for MED33 in plant immunity against necrotrophic fungal pathogens.
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville FL, USA.
authors.forename: Chenggang
authors.initials: C
authors.lastname: Wang
authors.affiliation: College of Life Science, Hubei University Wuhan, China.
authors.forename: Xuezhu
authors.initials: X
authors.lastname: Du
authors.affiliation: Department of Microbiology and Cell Science, University of Florida, Gainesville FL, USA.
authors.forename: Zhonglin
authors.initials: Z
authors.lastname: Mou
keywords: Arabidopsis; MED14; MED15; MED16; and ethylene; defense signaling crosstalk; jasmonate; salicylic acid