A plant＇s capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase （MAPK） cascades. In Arabidopsis thaliana, MPK3 is particularly strongly asso...A plant＇s capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase （MAPK） cascades. In Arabidopsis thaliana, MPK3 is particularly strongly associated with numerous abiotic and biotic stress responses. Identification of MPK3 substrates is a milestone towards improving stress resistance in plants. Here, we characterize AZI1, a lipid transfer protein （LTP）-related hybrid proline-rich protein （HyPRP）, as a novel target of MPK3. AZI1 is phosphorylated by MPK3 in vitro. As documented by co-immunoprecipitation and bimolecular fluorescence complementation experiments, AZI1 interacts with MPK3 to form protein complexes in planta. Furthermore, null mutants of azil are hypersensitive to salt stress, while AZIl-overexpressing lines are markedly more tolerant. AZI1 overexpression in the mpk3 genetic background partially alleviates the salt-hypersensitive phenotype of this mutant, but functional MPK3 appears to be required for the full extent of AZIl-conferred robustness. Notably, this robustness does not come at the expense of normal development. Immunoblot and RT-PCR data point to a role of MPK3 as positive regulator of AZI1 abundance.展开更多
The mitotic activity of root apical meristem(RAM)is critical to primary root growth and development.Previous studies have identified the roles of ROOT GROWTH FACTOR 1(RGF1),a peptide ligand,and its receptors,RGF1 INSE...The mitotic activity of root apical meristem(RAM)is critical to primary root growth and development.Previous studies have identified the roles of ROOT GROWTH FACTOR 1(RGF1),a peptide ligand,and its receptors,RGF1 INSENSITIVEs(RGIs),a clade of five leucine-rich-repeat receptor-like kinases,in promoting cell division in the RAM,which determines the primary root length.However,the downstream signaling components remain elusive.In this study,we identify a complete mitogen-activated protein kinase(MAPK or MPK)cascade,composed of YDA,MKK4/MKK5,and MPK3/MPK6,that functions downstream of the RGF1-RGI ligand-receptor pair.Similar to the rgi1/2/3/4/5 quintuple mutant,loss-of-function mutants of MPK3 and MPK6,MKK4 and MKK5,or YDA show a short-root phenotype,which is associated with reduced mitotic activity and lower expression of PLETHORA 1(PLT1)/PLT2 in the RAM.Furthermore,MPK3/MPK6 activation in response to exogenous RGF1 treatment is impaired in the rgi1/2/3/4/5 quintuple,yda single,and mkk4 m kk5 double mutants.Epistatic analyses demonstrated that the expression of constitutively active MKK4,MKK5,or YDA driven by the RGI2 promoter can rescue the short-root phenotype of the rgi1/2/3/4/5 mutant.Taken together,these results suggest that the YDA-MKK4/MKK5-MPK3/MPK6 cascade functions downstream of the RGF1-RGI ligand-receptor pair and upstream of PLT1/PLT2 to modulate the stem cell population and primary root growth in Arabidopsis.展开更多
The plant cell wall is composed of a matrix of cellulose fibers, flexible pectin polymers, and an array of as- sorted carbohydrates and proteins. The receptor-like Wall-Associated Kinases （WAKs） of Arabidopsis bind ...The plant cell wall is composed of a matrix of cellulose fibers, flexible pectin polymers, and an array of as- sorted carbohydrates and proteins. The receptor-like Wall-Associated Kinases （WAKs） of Arabidopsis bind pectin in the wall, and are necessary both for cell expansion during development and for a response to pathogens and wounding. Mitogen Activated Protein Kinases （MPKs） form a major signaling link between cell surface receptors and both transcrip- tional and enzyme regulation in eukaryotes, and Arabidopsis MPK6 and MPK3 indeed have important roles in develop- ment and the response to stress and pathogens. A dominant allele of WAK2 requires kinase activity and activates a stress response that includes an increased ROS accumulation and the up-regulation of numerous genes involved in pathogen resistance, wounding, and cell wall biogenesis. This dominant allele requires a functional pectin binding and kinase domain, indicating that it is engaged in a WAK signaling pathway. A null mutant of the major plasma membrane ROS-producing enzyme complex, rbohd/f does not suppress the WAK2cTAP-induced phenotype. A mpk6, but not a mpk3, null allele is able to suppress the effects of this dominant WAK2 mutation, thus distinguishing MPK3 and MPK6, whose activity previously was thought to be redundant. Pectin activation of gene expression is abated in a wak2-null, but is tempered by the WAK-dominant allele that induces elevated basal stress-related transcript levels. The results suggest a mechanism in which changes to the cell wall can lead to a large change in cellular responses and help to explain how pathogens and wounding can have general effects on growth.展开更多
Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3(MAPK3 or MPK3)and MPK6 play important signaling roles in plant immunity and growth/development.MAPK KINASE4(MKK4)and MKK5 function redundantly upstream of MPK3 and MPK6 in...Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3(MAPK3 or MPK3)and MPK6 play important signaling roles in plant immunity and growth/development.MAPK KINASE4(MKK4)and MKK5 function redundantly upstream of MPK3 and MPK6 in these processes.YODA(YDA),also known as MAPK KINASE KINASE4(MAPKKK4),is upstream of MKK4/MKK5 and forms a complete MAPK cascade(YDA–MKK4/MKK5–MPK3/MPK6)in regulating plant growth and development.In plant immunity,MAPKKK3 and MAPKKK5 function redundantly upstream of the same MKK4/MKK5–MPK3/MPK6 module.However,the residual activation of MPK3/MPK6 in the mapkkk3 mapkkk5 double mutant in response to flg22 pathogen-associated molecular pattern(PAMP)treatment suggests the presence of additional MAPKKK(s)in this MAPK cascade in signaling plant immunity.To investigate whether YDA is also involved in plant immunity,we attempted to generate mapkkk3 mapkkk5 yda triple mutants.However,it was not possible to recover one of the double mutant combinations(mapkkk5 yda)or the triple mutant(mapkkk3 mapkkk5 yda)due to a failure of embryogenesis.Using the clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPRassociated protein 9(Cas9)approach,we generated weak,N-terminal deletion alleles of YDA,yda-del,in a mapkkk3 mapkkk5 background.PAMP-triggered MPK3/MPK6 activation was further reduced in the mapkkk3 mapkkk5 yda-del mutant,and the triple mutant was more susceptible to pathogen infection,suggesting YDA also plays an important role in plant immune signaling.In addition,MAPKKK5 and,to a lesser extent,MAPKKK3 were found to contribute to gamete function and embryogenesis,together with YDA.While the double homozygous mapkkk3 yda mutant showed the same growth and development defects as the yda single mutant,mapkkk5 yda double mutant and mapkkk3 mapkkk5 yda triple mutants were embryo lethal,similar to the mpk3 mpk6 double mutants.These results demonstrate that YDA,MAPKKK3,and MAPKKK5 have overlapping functions upstream of the MKK4/MKK5–MPK3/MPK6 module in both plant immunity and growth/development.展开更多
The plant signaling pathway that regulates pathogen-associated molecular pattern(PAMP)-triggered immunity(PTI)involves mitogen-activated protein kinase(MAPK)cascades that comprise sequential activation of several prot...The plant signaling pathway that regulates pathogen-associated molecular pattern(PAMP)-triggered immunity(PTI)involves mitogen-activated protein kinase(MAPK)cascades that comprise sequential activation of several protein kinases and the ensuing phosphorylation of MAPKs,which activate transcription factors(TFs)to promote downstream defense responses.To identify plant TFs that regulate MAPKs,we investigated TF-defective mutants of Arabidopsis thaliana and identified MYB44 as an essential constituent of the PTI pathway.MYB44 confers resistance against the bacterial pathogen Pseudomonas syringae by cooperating with MPK3 and MPK6.Under PAMP treatment,MYB44 binds to the promoters of MPK3 and MPK6 to activate their expression,leading to phosphorylation of MPK3 and MPK6 proteins.In turn,phosphorylated MPK3 and MPK6 phosphorylate MYB44 in a functionally redundant manner,thus enabling MYB44 to activate MPK3 and MPK6 expression and further activate downstream defense responses.Activation of defense responses has also been attributed to activation of EIN2 transcription by MYB44,which has previously been shown to affect PAMP recognition and PTI development.AtMYB44 thus functions as an integral component of the PTI pathway by connecting transcriptional and posttranscriptional regulation of the MPK3/6 cascade.展开更多
Mitogen-activated protein kinase(MAPK)cascades have been discovered to play a fundamental role in regulating organ abscission.However,the identity of protein substrates targeted by MAPK cascades,as well as whether the...Mitogen-activated protein kinase(MAPK)cascades have been discovered to play a fundamental role in regulating organ abscission.However,the identity of protein substrates targeted by MAPK cascades,as well as whether the role of MAPK protein cascades in the abscission process is conserved across different plant species,remain unknown.Here,the role of homologs of MPK3 and MPK6 in regulating fruit abscission were characterized in litchi.Ectopic expression of LcMPK3 or LcMPK6 in Arabidopsis mpk3 mpk6 mutant rescued the deficiency in floral organ abscission,while silencing of LcMPK3 or LcMPK6 in litchi significantly decreased fruitlet abscission.Importantly,a total of 49 proteins interacting with LcMPK3 were identified through yeast two-hybrid screening,including two components of the MAPK signaling cascade,five transcription factors,and two aquaporins.Furthermore,the interaction between LcMPK3/6 with LcBZR1/2,core components in brassinosteroids signaling that suppress litchi fruitlet abscission,was confirmed using in vitro and in vivo assays.Moreover,phos-tag assays demonstrated that LcMPK3/6 could phosphorylate LcBZR1/2,with several phosphorylation residues identified.Together,our findings suggest that LcMPK3 and LcMPK6 play a positive regulatory role in fruitlet abscission in litchi,and offer crucial information for the investigation of mechanisms underlying MPK3/6-mediated organ abscission in plants.展开更多
The nuclear pore complex(NPC),the sole exchange channel between the nucleus and cytoplasm,is composed of several subcomplexes,among which the central barrier determines the permeability/selectivity of the NPC to domin...The nuclear pore complex(NPC),the sole exchange channel between the nucleus and cytoplasm,is composed of several subcomplexes,among which the central barrier determines the permeability/selectivity of the NPC to dominate the nucleocytoplasmic trafficking essential for many important signaling events in yeast and mammals.How plant NPC central barrier controls selective transport is a crucial question remaining to be elucidated.In this study,we uncovered that phase separation of the central barrier is critical for the permeability and selectivity of plant NPC in the regulation of various biotic stresses.Phenotypic assays of nup62 mutants and complementary lines showed that NUP62 positively regulates plant defense against Botrytis cinerea,one of the world’s most disastrous plant pathogens.Furthermore,in vivo imaging and in vitro biochemical evidence revealed that plant NPC central barrier undergoes phase separation to regulate selective nucleocytoplasmic transport of immune regulators,as exemplified by MPK3,essential for plant resistance to B.cinerea.Moreover,genetic analysis demonstrated that NPC phase separation plays an important role in plant defense against fungal and bacterial infection as well as insect attack.These findings reveal that phase separation of the NPC central barrier serves as an important mechanism to mediate nucleocytoplasmic transport of immune regulators and activate plant defense against a broad range of biotic stresses.展开更多
Adventitious roots form from non-root tissues as part of normal development or in response to stress or wounding.The root primordia form in the source tissue,and during emergence the adventitious roots penetrate the i...Adventitious roots form from non-root tissues as part of normal development or in response to stress or wounding.The root primordia form in the source tissue,and during emergence the adventitious roots penetrate the inner cell layers and the epidermis;however,the mechanisms underlying this emergence remain largely unexplored.Here,we report that a regulatory module composed of the AP2/ERF transcription factor ABSCISIC ACID INSENSITIVE 4(ABI4),the MAP kinases MPK3 and MPK6,and the phosphatase PP2C12 plays an important role in the emergence of junction adventitious roots(J-ARs)from the root-hypocotyl junctions in Arabidopsis thaliana.ABI4 negatively regulates J-AR emergence,preventing the accumulation of reactive oxygen species and death of epidermal cells,which would otherwise facilitate J-AR emergence.Phosphorylation by MPK3/MPK6 activates ABI4 and dephosphorylation by PP2C12 inactivates ABI4.MPK3/MPK6 also directly phosphorylate and inactivate PP2C12 during J-AR emergence.We propose that this"double-check"mechanism increases the robustness of MAP kinase signaling and finely regulates the local programmed cell death required for J-AR emergence.展开更多
文摘A plant＇s capability to cope with environmental challenges largely relies on signal transmission through mitogen-activated protein kinase （MAPK） cascades. In Arabidopsis thaliana, MPK3 is particularly strongly associated with numerous abiotic and biotic stress responses. Identification of MPK3 substrates is a milestone towards improving stress resistance in plants. Here, we characterize AZI1, a lipid transfer protein （LTP）-related hybrid proline-rich protein （HyPRP）, as a novel target of MPK3. AZI1 is phosphorylated by MPK3 in vitro. As documented by co-immunoprecipitation and bimolecular fluorescence complementation experiments, AZI1 interacts with MPK3 to form protein complexes in planta. Furthermore, null mutants of azil are hypersensitive to salt stress, while AZIl-overexpressing lines are markedly more tolerant. AZI1 overexpression in the mpk3 genetic background partially alleviates the salt-hypersensitive phenotype of this mutant, but functional MPK3 appears to be required for the full extent of AZIl-conferred robustness. Notably, this robustness does not come at the expense of normal development. Immunoblot and RT-PCR data point to a role of MPK3 as positive regulator of AZI1 abundance.
基金grants from the National Natural Science Foundation of China(31922005)the Natural Science Foundation of Zhejiang Province(LR18C020001)+1 种基金the Young Elite Scientist Sponsorship Program of China Association for Science and Technology(CAST)(2018QNRC001)111 Project(B14027)to J.X.
文摘The mitotic activity of root apical meristem(RAM)is critical to primary root growth and development.Previous studies have identified the roles of ROOT GROWTH FACTOR 1(RGF1),a peptide ligand,and its receptors,RGF1 INSENSITIVEs(RGIs),a clade of five leucine-rich-repeat receptor-like kinases,in promoting cell division in the RAM,which determines the primary root length.However,the downstream signaling components remain elusive.In this study,we identify a complete mitogen-activated protein kinase(MAPK or MPK)cascade,composed of YDA,MKK4/MKK5,and MPK3/MPK6,that functions downstream of the RGF1-RGI ligand-receptor pair.Similar to the rgi1/2/3/4/5 quintuple mutant,loss-of-function mutants of MPK3 and MPK6,MKK4 and MKK5,or YDA show a short-root phenotype,which is associated with reduced mitotic activity and lower expression of PLETHORA 1(PLT1)/PLT2 in the RAM.Furthermore,MPK3/MPK6 activation in response to exogenous RGF1 treatment is impaired in the rgi1/2/3/4/5 quintuple,yda single,and mkk4 m kk5 double mutants.Epistatic analyses demonstrated that the expression of constitutively active MKK4,MKK5,or YDA driven by the RGI2 promoter can rescue the short-root phenotype of the rgi1/2/3/4/5 mutant.Taken together,these results suggest that the YDA-MKK4/MKK5-MPK3/MPK6 cascade functions downstream of the RGF1-RGI ligand-receptor pair and upstream of PLT1/PLT2 to modulate the stem cell population and primary root growth in Arabidopsis.
文摘The plant cell wall is composed of a matrix of cellulose fibers, flexible pectin polymers, and an array of as- sorted carbohydrates and proteins. The receptor-like Wall-Associated Kinases （WAKs） of Arabidopsis bind pectin in the wall, and are necessary both for cell expansion during development and for a response to pathogens and wounding. Mitogen Activated Protein Kinases （MPKs） form a major signaling link between cell surface receptors and both transcrip- tional and enzyme regulation in eukaryotes, and Arabidopsis MPK6 and MPK3 indeed have important roles in develop- ment and the response to stress and pathogens. A dominant allele of WAK2 requires kinase activity and activates a stress response that includes an increased ROS accumulation and the up-regulation of numerous genes involved in pathogen resistance, wounding, and cell wall biogenesis. This dominant allele requires a functional pectin binding and kinase domain, indicating that it is engaged in a WAK signaling pathway. A null mutant of the major plasma membrane ROS-producing enzyme complex, rbohd/f does not suppress the WAK2cTAP-induced phenotype. A mpk6, but not a mpk3, null allele is able to suppress the effects of this dominant WAK2 mutation, thus distinguishing MPK3 and MPK6, whose activity previously was thought to be redundant. Pectin activation of gene expression is abated in a wak2-null, but is tempered by the WAK-dominant allele that induces elevated basal stress-related transcript levels. The results suggest a mechanism in which changes to the cell wall can lead to a large change in cellular responses and help to explain how pathogens and wounding can have general effects on growth.
基金supported by a grant from the National Science Foundation to S.Z.(Award 1856093)。
文摘Arabidopsis MITOGEN-ACTIVATED PROTEIN KINASE3(MAPK3 or MPK3)and MPK6 play important signaling roles in plant immunity and growth/development.MAPK KINASE4(MKK4)and MKK5 function redundantly upstream of MPK3 and MPK6 in these processes.YODA(YDA),also known as MAPK KINASE KINASE4(MAPKKK4),is upstream of MKK4/MKK5 and forms a complete MAPK cascade(YDA–MKK4/MKK5–MPK3/MPK6)in regulating plant growth and development.In plant immunity,MAPKKK3 and MAPKKK5 function redundantly upstream of the same MKK4/MKK5–MPK3/MPK6 module.However,the residual activation of MPK3/MPK6 in the mapkkk3 mapkkk5 double mutant in response to flg22 pathogen-associated molecular pattern(PAMP)treatment suggests the presence of additional MAPKKK(s)in this MAPK cascade in signaling plant immunity.To investigate whether YDA is also involved in plant immunity,we attempted to generate mapkkk3 mapkkk5 yda triple mutants.However,it was not possible to recover one of the double mutant combinations(mapkkk5 yda)or the triple mutant(mapkkk3 mapkkk5 yda)due to a failure of embryogenesis.Using the clustered regularly interspaced short palindromic repeats(CRISPR)–CRISPRassociated protein 9(Cas9)approach,we generated weak,N-terminal deletion alleles of YDA,yda-del,in a mapkkk3 mapkkk5 background.PAMP-triggered MPK3/MPK6 activation was further reduced in the mapkkk3 mapkkk5 yda-del mutant,and the triple mutant was more susceptible to pathogen infection,suggesting YDA also plays an important role in plant immune signaling.In addition,MAPKKK5 and,to a lesser extent,MAPKKK3 were found to contribute to gamete function and embryogenesis,together with YDA.While the double homozygous mapkkk3 yda mutant showed the same growth and development defects as the yda single mutant,mapkkk5 yda double mutant and mapkkk3 mapkkk5 yda triple mutants were embryo lethal,similar to the mpk3 mpk6 double mutants.These results demonstrate that YDA,MAPKKK3,and MAPKKK5 have overlapping functions upstream of the MKK4/MKK5–MPK3/MPK6 module in both plant immunity and growth/development.
基金supported by the Natural Science Foundation of China(grant numbers 31772247,32072399,32170202)the Natural Science Foundation of Shandong Province(grant numbers ZR2020MC113,ZR2020MC120,ZR2020QC126).
文摘The plant signaling pathway that regulates pathogen-associated molecular pattern(PAMP)-triggered immunity(PTI)involves mitogen-activated protein kinase(MAPK)cascades that comprise sequential activation of several protein kinases and the ensuing phosphorylation of MAPKs,which activate transcription factors(TFs)to promote downstream defense responses.To identify plant TFs that regulate MAPKs,we investigated TF-defective mutants of Arabidopsis thaliana and identified MYB44 as an essential constituent of the PTI pathway.MYB44 confers resistance against the bacterial pathogen Pseudomonas syringae by cooperating with MPK3 and MPK6.Under PAMP treatment,MYB44 binds to the promoters of MPK3 and MPK6 to activate their expression,leading to phosphorylation of MPK3 and MPK6 proteins.In turn,phosphorylated MPK3 and MPK6 phosphorylate MYB44 in a functionally redundant manner,thus enabling MYB44 to activate MPK3 and MPK6 expression and further activate downstream defense responses.Activation of defense responses has also been attributed to activation of EIN2 transcription by MYB44,which has previously been shown to affect PAMP recognition and PTI development.AtMYB44 thus functions as an integral component of the PTI pathway by connecting transcriptional and posttranscriptional regulation of the MPK3/6 cascade.
基金supported by grants from the Natural Science Foundation of Guangdong Province,China(2021B1515120082)the National Natural Science Foundation of China(32330092 and 32072544).
文摘Mitogen-activated protein kinase(MAPK)cascades have been discovered to play a fundamental role in regulating organ abscission.However,the identity of protein substrates targeted by MAPK cascades,as well as whether the role of MAPK protein cascades in the abscission process is conserved across different plant species,remain unknown.Here,the role of homologs of MPK3 and MPK6 in regulating fruit abscission were characterized in litchi.Ectopic expression of LcMPK3 or LcMPK6 in Arabidopsis mpk3 mpk6 mutant rescued the deficiency in floral organ abscission,while silencing of LcMPK3 or LcMPK6 in litchi significantly decreased fruitlet abscission.Importantly,a total of 49 proteins interacting with LcMPK3 were identified through yeast two-hybrid screening,including two components of the MAPK signaling cascade,five transcription factors,and two aquaporins.Furthermore,the interaction between LcMPK3/6 with LcBZR1/2,core components in brassinosteroids signaling that suppress litchi fruitlet abscission,was confirmed using in vitro and in vivo assays.Moreover,phos-tag assays demonstrated that LcMPK3/6 could phosphorylate LcBZR1/2,with several phosphorylation residues identified.Together,our findings suggest that LcMPK3 and LcMPK6 play a positive regulatory role in fruitlet abscission in litchi,and offer crucial information for the investigation of mechanisms underlying MPK3/6-mediated organ abscission in plants.
基金supported by funding from the National Natural Science Foundation of China(32250001 and 31830008 to D.X.,32150023 and 32125010 to P.L.,and 31901570 to D.W.)the National Key Research and Development Program of China(2019YFA0508403 to P.L.)+1 种基金the China Postdoctoral Science Foundation(2018M631447 to J.W.)a postdoctoral fellowship of the Tsinghua-Peking Joint Center for Life Sciences.
文摘The nuclear pore complex(NPC),the sole exchange channel between the nucleus and cytoplasm,is composed of several subcomplexes,among which the central barrier determines the permeability/selectivity of the NPC to dominate the nucleocytoplasmic trafficking essential for many important signaling events in yeast and mammals.How plant NPC central barrier controls selective transport is a crucial question remaining to be elucidated.In this study,we uncovered that phase separation of the central barrier is critical for the permeability and selectivity of plant NPC in the regulation of various biotic stresses.Phenotypic assays of nup62 mutants and complementary lines showed that NUP62 positively regulates plant defense against Botrytis cinerea,one of the world’s most disastrous plant pathogens.Furthermore,in vivo imaging and in vitro biochemical evidence revealed that plant NPC central barrier undergoes phase separation to regulate selective nucleocytoplasmic transport of immune regulators,as exemplified by MPK3,essential for plant resistance to B.cinerea.Moreover,genetic analysis demonstrated that NPC phase separation plays an important role in plant defense against fungal and bacterial infection as well as insect attack.These findings reveal that phase separation of the NPC central barrier serves as an important mechanism to mediate nucleocytoplasmic transport of immune regulators and activate plant defense against a broad range of biotic stresses.
基金This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciencesthe Ministry of Agriculture of China(grant no.2016ZX08009003-005).
文摘Adventitious roots form from non-root tissues as part of normal development or in response to stress or wounding.The root primordia form in the source tissue,and during emergence the adventitious roots penetrate the inner cell layers and the epidermis;however,the mechanisms underlying this emergence remain largely unexplored.Here,we report that a regulatory module composed of the AP2/ERF transcription factor ABSCISIC ACID INSENSITIVE 4(ABI4),the MAP kinases MPK3 and MPK6,and the phosphatase PP2C12 plays an important role in the emergence of junction adventitious roots(J-ARs)from the root-hypocotyl junctions in Arabidopsis thaliana.ABI4 negatively regulates J-AR emergence,preventing the accumulation of reactive oxygen species and death of epidermal cells,which would otherwise facilitate J-AR emergence.Phosphorylation by MPK3/MPK6 activates ABI4 and dephosphorylation by PP2C12 inactivates ABI4.MPK3/MPK6 also directly phosphorylate and inactivate PP2C12 during J-AR emergence.We propose that this"double-check"mechanism increases the robustness of MAP kinase signaling and finely regulates the local programmed cell death required for J-AR emergence.
