Botrytis cinerea-induced F-box protein 1 enhances disease resistance by inhibiting JAO/JOX-mediated jasmonic acid catabolism in Arabidopsis

Jasmonic acid(JA)is a crucial phytohormone that regulates plant immunity.The endogenous JA level is determined by the rates of its biosynthesis and catabolism in plants.The activation of JA biosynthesis has been well documented;however,how plants repress JA catabolism upon pathogen infection remains elusive.In this study,we identified and characterized Botrytis cinerea-induced F-box protein 1(BFP1)in Arabidopsis.The expression of BFP1 was induced by B.cinerea in a JA signaling-dependent manner,and BFP1 protein was critical for plant defense against B.cinerea and plant response to JA.In addition,BFP1 overexpression increased plant defenses against broad-spectrum pathogens without fitness costs.Further experiments demonstrated that BFP1 interacts with and mediates the ubiquitination and degrada-tion of jasmonic acid oxidases(JAOs,also known as jasmonate-induced oxygenases,JoXs),the enzymes that hydroxylate JA to 12OH-JA.Consistent with this,BFP1 affects the accumulation of JA and 12OH-JA during B.cinerea infection.Moreover,mutation of JAo2 complemented the phenotypes of the bfp1 mutant.Collectively,our results unveil a new mechanism used by plants to activate immune responses upon path-ogeninfection:suppressing JA catabolism.

PLEK2 promotes cancer stemness and tumorigenesis of head and neck squamous cell carcinoma via the c-Myc-mediated positive feedback loop

Background:Head and neck squamous cell carcinoma(HNSCC)is one of the most frequent malignancies worldwide and is characterized by unfavorable prognosis,high lymph node metastasis and early recurrence.However,the molecular events regulating HNSCC tumorigenesis remain poorly understood.Therefore,uncovering the underlying mechanisms is urgently needed to identify novel and promising therapeutic targets for HNSCC.In this study,we aimed to explore the role of pleckstrin-2(PLEK2)in regulating HNSCC tumorigenesis.Methods:The expression pattern of PLEK2 and its clinical significance in HNSCC were determined by analyzing publicly assessable datasets and our own independent HNSCC cohort.In vitro and in vivo experiments,including cell proliferation,colony formation,Matrigel invasion,tumor sphere formation,ALDEFLUOR,Western blotting assays and xenograft mouse models,were used to investigate the role of PLEK2 in regulating the malignant behaviors of HNSCC cells.The underlying molecular mechanisms for the tumor-promoting role of PLEK2 were elucidated using co-immunoprecipitation,cycloheximide chase analysis,ubiquitination assays,chromatin immunoprecipitation-quantitative polymerase chain reaction,luciferase reporter assays and rescue experiments.Results:The expression levels of PLEK2 mRNA and protein were significantly increased in HNSCC tissues,and PLEK2 overexpression was strongly associated with poor overall survival and therapeutic resistance.Additionally,PLEK2 was important for maintaining the proliferation,invasion,epithelial-mesenchymal transition,cancer stemness and tumorigenesis of HNSCC cells and could alter the cellular metabolism of the cancer cells.Mechanistically,PLEK2 interacted with c-Myc and reduced the association of F-box and WD repeat domain containing 7(FBXW7)with c-Myc,thereby avoiding ubiquitination and subsequent proteasome-mediated degradation of c-Myc.Moreover,the c-Myc signaling activated by PLEK2 was important for sustaining the aggressive malignant phenotypes and tumorigenesis of HNSCC cells.c-Myc also directly bounded to the PLEK2 promoter and activated its transcription,forming a positive feedback loop.Conclusions:Collectively,these findings uncover a previously unknown molecular basis of PLEK2-enhanced c-Myc signaling in HNSCC,suggesting that PLEK2 may represent a promising therapeutic target for treating HNSCC.