title: Mitogen-activated protein kinase 6 regulates NPR1 gene expression and activation during leaf senescence induced by salicylic acid.
abstract: Plant senescence is a highly regulated process that can be induced by a range of factors. The nonexpressor of pathogenesis-related genes 1 (npr1) mutant is defective in the salicylic acid (SA) signalling pathway, displaying delayed yellowing during developmental senescence. However, the regulating mechanism of NPR1 on exogenous SA-induced senescence in detached Arabidopsis leaves has not yet been clarified. It was shown here that mitogen-activated protein kinase 6 (MPK6) is involved in promoting exogenous SA-induced detached leaf senescence. During the process of SA-induced senescence, the expression of NPR1 and senescence-related transcription factor WRKY6 was suppressed in mpk6 mutant plants. Further analyses showed that the NPR1 mRNA level is reduced in wrky6 mutants and enhanced in WRKY6 overexpressing lines. Meanwhile, chromatin immunoprecipitation experiments revealed that WRKY6 binds directly to the NPR1 promoter containing W-box motifs. Moreover, inhibition of MPK6 function diminished SA-induced monomerization and nuclear localization of NPR1. In addition, the expression of Trx h5, which catalyses the SA-induced NPR1 activation, was suppressed in the mpk6 mutant, suggesting that MPK6 promotes NPR1 activation, possibly by regulating the expression of Trx h5. Collectively, MPK6-mediated WRKY6 and Trx h5 transcriptional activation co-regulated the expression of the NPR1 gene and the monomerization of NPR1 protein, allowing it to enter the nucleus, thereby promoting SA-induced leaf senescence. These results provide new insight into the mechanism of exogenous SA-induced detached leaf senescence.
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Chai
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Liu
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China.
authors.forename: Jun
authors.initials: J
authors.lastname: Zhou
authors.affiliation: MOE Key Laboratory of Laser Life Science & Institute of Laser Life Science, College of Biophotonics, South China Normal University, Guangzhou 510631, China xingda@scnu.edu.cn.
authors.forename: Da
authors.initials: D
authors.lastname: Xing
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism*; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D005419:Flavonoids / Q000494:pharmacology; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008954:Models, Biological; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018515:Plant Leaves / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects / Q000235:genetics; D021381:Protein Transport / Q000187:drug effects; D020156:Salicylic Acid / Q000494:pharmacology*; D054480:Thioredoxin h / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
chemical_list: C504905:ATTRX1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D005419:Flavonoids; C105496:NPR1 protein, Arabidopsis; D054480:Thioredoxin h; D014157:Transcription Factors; C446285:WRKY6 protein, Arabidopsis; D049452:Green Fluorescent Proteins; C436293:MPK6 protein, Arabidopsis; D020928:Mitogen-Activated Protein Kinases; D020156:Salicylic Acid; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one
keywords: Arabidopsis; MPK6; NPR1; Trx h5; WRKY6.; salicylic acid; senescence