Hormonal crosstalk is central for tailoring plant responses to the nature of challenges encountered. The role of antagonism between the two major defense hormones, salicylic acid （SA） and jasmonic acid （JA）, and m...Hormonal crosstalk is central for tailoring plant responses to the nature of challenges encountered. The role of antagonism between the two major defense hormones, salicylic acid （SA） and jasmonic acid （JA）, and modulation of this interplay by ethylene （ET） in favor of JA signaling pathway in plant stress responses is well recognized, but the underlying mechanism is not fully understood. Here, we show the opposing function of two transcription factors, ethylene insensitive3 （EIN3） and EIN3-Like1 （EIL1）, in SA-mediated suppression and JA- mediated activation of PLANT DEFENSINI.2 （PDFI.2）. This functional duality is mediated via their effect on protein, not transcript levels of the PDF1.2 transcriptional activator octadecanoid-responsive Arabidopsis59 （ORA59）. Specifically, JA induces ORA59 protein levels independently of EIN3/EIL1, whereas SA reduces the protein levels dependently of EIN3/EIL1. Co-infiltration assays revealed nuclear co-localization of ORA59 and EIN3, and split- luciferase together with yeast-two-hybrid assays established their physical interaction. The functional ramification of the physical interaction is EIN3-dependent degradation of ORA59 by the 26S proteasome. These findings allude to SA-responsive reduction of ORA59 levels mediated by EIN3 binding to and targeting of ORA59 for degrada4tion, thus nominating ORA59 pool as a coordination node for the antagonistic function of ET/JA and SA.展开更多
Mediator,a conserved multiprotein complex in animals,plants,and fungi,is a cofactor of RNA polymerase II(Pol II).It is known to promote basal Pol II-mediated transcription as well as bridge sequence-specific transcrip...Mediator,a conserved multiprotein complex in animals,plants,and fungi,is a cofactor of RNA polymerase II(Pol II).It is known to promote basal Pol II-mediated transcription as well as bridge sequence-specific transcriptional regulators and Pol II to integrate regulatory information.Pol II transcribes not only protein-coding genes but also intergenic regions to generate noncoding RNAs such as small RNAs(microRNAs and small interfering RNAs)and long noncoding RNAs.Intriguingly,two plant-specific polymerases,Pol IV and Pol V,have evolved from Pol II and play a role in the production of small interfering RNAs and long noncoding RNAs at heterochromatic regions to maintain genome stability through transcriptional gene silencing(TGS).Recent studies have defined the composition of the plant Mediator and evaluated its role in noncoding RNA production in relationship to Pol II,Pol IV and Pol V.Here,we review the functions of Mediator and that of noncoding RNAs generated by Pol II,Pol IV and Pol V in plants,and discuss a role of Mediator in epigenetic regulation via noncoding RNA production.展开更多
基金supported by National Institutes of Health(R01GM107311)National Science Foundation(IOS-1036491and IOS1352478) grants awarded to K.D.
文摘Hormonal crosstalk is central for tailoring plant responses to the nature of challenges encountered. The role of antagonism between the two major defense hormones, salicylic acid （SA） and jasmonic acid （JA）, and modulation of this interplay by ethylene （ET） in favor of JA signaling pathway in plant stress responses is well recognized, but the underlying mechanism is not fully understood. Here, we show the opposing function of two transcription factors, ethylene insensitive3 （EIN3） and EIN3-Like1 （EIL1）, in SA-mediated suppression and JA- mediated activation of PLANT DEFENSINI.2 （PDFI.2）. This functional duality is mediated via their effect on protein, not transcript levels of the PDF1.2 transcriptional activator octadecanoid-responsive Arabidopsis59 （ORA59）. Specifically, JA induces ORA59 protein levels independently of EIN3/EIL1, whereas SA reduces the protein levels dependently of EIN3/EIL1. Co-infiltration assays revealed nuclear co-localization of ORA59 and EIN3, and split- luciferase together with yeast-two-hybrid assays established their physical interaction. The functional ramification of the physical interaction is EIN3-dependent degradation of ORA59 by the 26S proteasome. These findings allude to SA-responsive reduction of ORA59 levels mediated by EIN3 binding to and targeting of ORA59 for degrada4tion, thus nominating ORA59 pool as a coordination node for the antagonistic function of ET/JA and SA.
文摘Mediator,a conserved multiprotein complex in animals,plants,and fungi,is a cofactor of RNA polymerase II(Pol II).It is known to promote basal Pol II-mediated transcription as well as bridge sequence-specific transcriptional regulators and Pol II to integrate regulatory information.Pol II transcribes not only protein-coding genes but also intergenic regions to generate noncoding RNAs such as small RNAs(microRNAs and small interfering RNAs)and long noncoding RNAs.Intriguingly,two plant-specific polymerases,Pol IV and Pol V,have evolved from Pol II and play a role in the production of small interfering RNAs and long noncoding RNAs at heterochromatic regions to maintain genome stability through transcriptional gene silencing(TGS).Recent studies have defined the composition of the plant Mediator and evaluated its role in noncoding RNA production in relationship to Pol II,Pol IV and Pol V.Here,we review the functions of Mediator and that of noncoding RNAs generated by Pol II,Pol IV and Pol V in plants,and discuss a role of Mediator in epigenetic regulation via noncoding RNA production.
