Mitogen-activated protein kinase （MAPK） cascades play important roles in regulating plant innate immune responses. In a genetic screen to search for mutants with constitutive defense responses, we identified multipl...Mitogen-activated protein kinase （MAPK） cascades play important roles in regulating plant innate immune responses. In a genetic screen to search for mutants with constitutive defense responses, we identified multiple alleles of mpk4 and mekkl that exhibit cell death and constitutive defense responses. Bimolecular fluorescence complemen- tation （BiFC） analysis showed that both MPK4 and MEKK1 interact with MKK1 and MKK2, two closely related MAPK kinases, mkkl and mkk2 single mutant plants do not have obvious mutant phenotypes. To test whether MKK1 and MKK2 function redundantly, mkkl mkk2 double mutants were generated. The mkkl mkk2 double mutant plants die at seedling stage and the seedling-lethality phenotype is temperature-dependent. Similar to the mpk4 and mekkl mutants, the mkkl mkk2 double mutant seedlings accumulate high levels of H202, display spontaneous cell death, constitutively express Pathogenesis Related （PR） genes and exhibit pathogen resistance. In addition, activation of MPK4 by fig22 is impaired in the mkkl mkk2 double mutants, suggesting that MKK1 and MKK2 function together with MPK4 and MEKK1 in a MAP kinase cascade to negatively regulate innate immune responses in plants.展开更多
Mitogen-activated protein kinase(MAPK)cascades play important roles in disease resistance in model plant species.However,the functions of MAPK signaling pathways in crop disease resistance are largely unknown.Here we ...Mitogen-activated protein kinase(MAPK)cascades play important roles in disease resistance in model plant species.However,the functions of MAPK signaling pathways in crop disease resistance are largely unknown.Here we report the function of HvMKK1-HvMPK4-HvWRKY1 module in barley immune system.HvMPK4 is identified to play a negative role in barley immune response against Bgh,as virus-induced gene silencing of HvMPK4 results in enhanced disease resistance whilst stably overexpressing HvMPK4 leads to super-susceptibility to Bgh infection.Furthermore,the barley MAPK kinase HvMKK1 is found to specifically interact with HvMPK4,and the activated HvMKK1^(DD) variant specifically phosphorylates HvMPK4 in vitro.Moreover,the transcription factor HvWRKY1 is identified to be a downstream target of HvMPK4 and phosphorylated by HvMPK4 in vitro in the presence of HvMKK1^(DD).Phosphorylation assay coupled with mutagenesis analyses identifies S122,T284,and S347 in HvWRKY1 as the major residues phosphorylated by HvMPK4.HvWRKY1 is phosphorylated in barley at the early stages of Bgh infection,which enhances its suppression on barley immunity likely due to enhanced DNA-binding and transcriptional repression activity.Our data suggest that the HvMKK1-HvMPK4 kinase pair acts upstream of HvWRKY1 to negatively regulate barley immunity against powdery mildew.展开更多
Over the last few years, it has become evident that reactive oxygen species （ROS） signalling plays an important role in various physiological responses, including pathogen defense and stomatal opening/closure. On th...Over the last few years, it has become evident that reactive oxygen species （ROS） signalling plays an important role in various physiological responses, including pathogen defense and stomatal opening/closure. On the other hand, ROS overproduction is detrimental for proper plant growth and development, indicating that the regulation of an appropriate redox balance is essential for plants. ROS homeostasis in plants involves the mitogen-activated protein kinase （MAPK） pathway consisting of the MAPK kinase kinase MEKK1 and the MAPK MPK4. Phenotypic and molecular analysis revealed that the MAPK kinases MKK1 and MKK2 are part of a cascade, regulating ROS and salicylic acid （SA） accumulation. Gene expression analysis shows that of 32 transcription factors reported to be highly responsive to multiple ROS-inducing conditions, 20 are regulated by the MEKK1, predominantly via the MEKK1-MKK1/2-MPK4 pathway. However, MEKK1 also functions on other as yet unknown pathways and part of the MEKK1-dependent MPK4 responses are regulated independently of MKK1 and MKK2. Overall, this analysis emphasizes the central role of this MAPK cascade in oxidative stress signalling, but also indicates the high level of complexity revealed by this signalling network.展开更多
Aluminum(Al)toxicity can seriously restrict crop production on acidic soils,which comprise 40%of the world’s potentially arable land.The zinc finger transcription factor STOP1 has a conserved and essential function i...Aluminum(Al)toxicity can seriously restrict crop production on acidic soils,which comprise 40%of the world’s potentially arable land.The zinc finger transcription factor STOP1 has a conserved and essential function in mediating plant Al resistance.Al stress induces STOP1 accumulation via post-transcriptional regulatory mechanisms.However,the upstream signaling pathway involved in Al-triggered STOP1 accumulation remains unclear.Here,we report that the MEKK1-MKK1/2-MPK4 cascade positively regulates STOP1 phosphorylation and stability.Mutations of MEKK1,MKK1/2,or MPK4 lead to decreased STOP1 stability and Al resistance.Al stress induces the kinase activity of MPK4,which interacts with and phosphorylates STOP1.The phosphorylation of STOP1 reduces its interaction with the F-box protein RAE1 that mediates STOP1 degradation,thereby leading to enhanced STOP1 stability and Al resistance.Taken together,our results suggest that the MEKK1-MKK1/2-MPK4 cascade is important for Al signaling and confers Al resistance through phosphorylation-mediated enhancement of STOP1 accumulation in Arabidopsis.展开更多
Disruption of the MEKK1-MKK1/MKK2-MPK4 kinase cascade leads to activation of immunity mediated by the nucleotide-binding leucine-rich repeat(NLR)immune receptor SUMM2,which monitors the phosphorylation status of CRCK3...Disruption of the MEKK1-MKK1/MKK2-MPK4 kinase cascade leads to activation of immunity mediated by the nucleotide-binding leucine-rich repeat(NLR)immune receptor SUMM2,which monitors the phosphorylation status of CRCK3.Here we report that two receptor-like kinases(RLKs),MDS1,and MDS2,function redundantly to promote SUMM2-mediated immunity.Activation of SUMM2-mediated immunity is dependent on MDS1,and to a less extent on MDS2.MDS1 associates with CRCK3 in planta and can phosphorylate CRCK3 in vitro,suggesting that it may target CRCK3 to positively regulate SUMM2-mediated signaling.Our finding highlights a new defense mechanism where RLKs promote NLR-mediated immunity.展开更多
文摘Mitogen-activated protein kinase （MAPK） cascades play important roles in regulating plant innate immune responses. In a genetic screen to search for mutants with constitutive defense responses, we identified multiple alleles of mpk4 and mekkl that exhibit cell death and constitutive defense responses. Bimolecular fluorescence complemen- tation （BiFC） analysis showed that both MPK4 and MEKK1 interact with MKK1 and MKK2, two closely related MAPK kinases, mkkl and mkk2 single mutant plants do not have obvious mutant phenotypes. To test whether MKK1 and MKK2 function redundantly, mkkl mkk2 double mutants were generated. The mkkl mkk2 double mutant plants die at seedling stage and the seedling-lethality phenotype is temperature-dependent. Similar to the mpk4 and mekkl mutants, the mkkl mkk2 double mutant seedlings accumulate high levels of H202, display spontaneous cell death, constitutively express Pathogenesis Related （PR） genes and exhibit pathogen resistance. In addition, activation of MPK4 by fig22 is impaired in the mkkl mkk2 double mutants, suggesting that MKK1 and MKK2 function together with MPK4 and MEKK1 in a MAP kinase cascade to negatively regulate innate immune responses in plants.
基金funded by the National Key R&D Program of China(2018YFD1000703 and 2018YFD1000700)the Strategic Priority Research Program of Chinese Academy of Sciences(XDPB16)National Program on Research and Development of Transgenic Plants(2016ZX08009-003-001).
文摘Mitogen-activated protein kinase(MAPK)cascades play important roles in disease resistance in model plant species.However,the functions of MAPK signaling pathways in crop disease resistance are largely unknown.Here we report the function of HvMKK1-HvMPK4-HvWRKY1 module in barley immune system.HvMPK4 is identified to play a negative role in barley immune response against Bgh,as virus-induced gene silencing of HvMPK4 results in enhanced disease resistance whilst stably overexpressing HvMPK4 leads to super-susceptibility to Bgh infection.Furthermore,the barley MAPK kinase HvMKK1 is found to specifically interact with HvMPK4,and the activated HvMKK1^(DD) variant specifically phosphorylates HvMPK4 in vitro.Moreover,the transcription factor HvWRKY1 is identified to be a downstream target of HvMPK4 and phosphorylated by HvMPK4 in vitro in the presence of HvMKK1^(DD).Phosphorylation assay coupled with mutagenesis analyses identifies S122,T284,and S347 in HvWRKY1 as the major residues phosphorylated by HvMPK4.HvWRKY1 is phosphorylated in barley at the early stages of Bgh infection,which enhances its suppression on barley immunity likely due to enhanced DNA-binding and transcriptional repression activity.Our data suggest that the HvMKK1-HvMPK4 kinase pair acts upstream of HvWRKY1 to negatively regulate barley immunity against powdery mildew.
文摘Over the last few years, it has become evident that reactive oxygen species （ROS） signalling plays an important role in various physiological responses, including pathogen defense and stomatal opening/closure. On the other hand, ROS overproduction is detrimental for proper plant growth and development, indicating that the regulation of an appropriate redox balance is essential for plants. ROS homeostasis in plants involves the mitogen-activated protein kinase （MAPK） pathway consisting of the MAPK kinase kinase MEKK1 and the MAPK MPK4. Phenotypic and molecular analysis revealed that the MAPK kinases MKK1 and MKK2 are part of a cascade, regulating ROS and salicylic acid （SA） accumulation. Gene expression analysis shows that of 32 transcription factors reported to be highly responsive to multiple ROS-inducing conditions, 20 are regulated by the MEKK1, predominantly via the MEKK1-MKK1/2-MPK4 pathway. However, MEKK1 also functions on other as yet unknown pathways and part of the MEKK1-dependent MPK4 responses are regulated independently of MKK1 and MKK2. Overall, this analysis emphasizes the central role of this MAPK cascade in oxidative stress signalling, but also indicates the high level of complexity revealed by this signalling network.
基金supported by the National Natural Science Foundation of China(grant nos.32170261 and 31870223 to C.-F.H.)the National Key Laboratory of Plant Molecular Genetics.
文摘Aluminum(Al)toxicity can seriously restrict crop production on acidic soils,which comprise 40%of the world’s potentially arable land.The zinc finger transcription factor STOP1 has a conserved and essential function in mediating plant Al resistance.Al stress induces STOP1 accumulation via post-transcriptional regulatory mechanisms.However,the upstream signaling pathway involved in Al-triggered STOP1 accumulation remains unclear.Here,we report that the MEKK1-MKK1/2-MPK4 cascade positively regulates STOP1 phosphorylation and stability.Mutations of MEKK1,MKK1/2,or MPK4 lead to decreased STOP1 stability and Al resistance.Al stress induces the kinase activity of MPK4,which interacts with and phosphorylates STOP1.The phosphorylation of STOP1 reduces its interaction with the F-box protein RAE1 that mediates STOP1 degradation,thereby leading to enhanced STOP1 stability and Al resistance.Taken together,our results suggest that the MEKK1-MKK1/2-MPK4 cascade is important for Al signaling and confers Al resistance through phosphorylation-mediated enhancement of STOP1 accumulation in Arabidopsis.
文摘Disruption of the MEKK1-MKK1/MKK2-MPK4 kinase cascade leads to activation of immunity mediated by the nucleotide-binding leucine-rich repeat(NLR)immune receptor SUMM2,which monitors the phosphorylation status of CRCK3.Here we report that two receptor-like kinases(RLKs),MDS1,and MDS2,function redundantly to promote SUMM2-mediated immunity.Activation of SUMM2-mediated immunity is dependent on MDS1,and to a less extent on MDS2.MDS1 associates with CRCK3 in planta and can phosphorylate CRCK3 in vitro,suggesting that it may target CRCK3 to positively regulate SUMM2-mediated signaling.Our finding highlights a new defense mechanism where RLKs promote NLR-mediated immunity.
