Like other eukaryotes,fungi use MAP kinase(MAPK)pathways to mediate cellular changes responding to external stimuli.In the past two decades,three well-conserved MAP kinase pathways have been characterized in various p...Like other eukaryotes,fungi use MAP kinase(MAPK)pathways to mediate cellular changes responding to external stimuli.In the past two decades,three well-conserved MAP kinase pathways have been characterized in various plant pathogenic fungi for regulating responses and adaptations to a variety of biotic and abiotic stresses encountered during plant infection or survival in nature.The invasive growth(IG)pathway is homologous to the yeast pheromone response and filamentation pathways.In plant pathogens,the IG pathway often is essential for pathogenesis by regulating infection-related morphogenesis,such as appressorium formation,penetration,and invasive growth.The cell wall integrity(CWI)pathway also is important for plant infection although the infection processes it regulates vary among fungal pathogens.Besides its universal function in cell wall integrity,it often plays a minor role in responses to oxidative and cell wall stresses.Both the IG and CWI pathways are involved in regulating known virulence factors as well as effector genes during plant infection and mediating defenses against mycoviruses,bacteria,and other fungi.In contrast,the high osmolarity growth(HOG)pathway is dispensable for virulence in some fungi although it is essential for plant infection in others.It regulates osmoregulation in hyphae and is dispensable for appressorium turgor generation.The HOG pathway also plays a major role for responding to oxidative,heat,and other environmental stresses and is overstimulated by phenylpyrrole fungicides.Moreover,these three MAPK pathways crosstalk and coordinately regulate responses to various biotic and abiotic stresses.The IG and CWI pathways,particularly the latter,also are involved in responding to abiotic stresses to various degrees in different fungal pathogens,and the HOG pathway also plays a role in interactions with other microbes or fungi.Furthermore,some infection processes or stress responses are co-regulated by MAPK pathways with cAMP or Ca^(2+)/CaM signaling.Overall,functions of individual MAP kinase pathways in pathogenesis and stress responses have been well characterized in a number of fungal pathogens,showing the conserved genetic elements with diverged functions,likely by rewiring transcriptional regulatory networks.In the near future,applications of genomics and proteomics approaches will likely lead to better understanding of crosstalk among the MAPKs and with other signaling pathways as well as roles of MAPKs in defense against other microbes(biotic interactions).展开更多
Mitogen-activated protein kinase(MAPK)cascades are activated by external stimuli and convert signals to cellular changes.Individual MAPKs have been characterized in a number of plant pathogenic fungi for their roles i...Mitogen-activated protein kinase(MAPK)cascades are activated by external stimuli and convert signals to cellular changes.Individual MAPKs have been characterized in a number of plant pathogenic fungi for their roles in pathogenesis and responses to biotic or abiotic stresses.However,mutants deleted of all the MAPK genes have not been reported in filamentous fungi.To determine the MAPK-less effects in a fungal pathogen,in this study we generated and characterized mutants deleted of all three MAPK genes in the wheat scab fungus Fusarium graminearum.The Gpmk1 mgv1 Fghog1 triple mutants had severe growth defects and was non-pathogenic.It was defective in infection cushion formation and DON production.Conidiation was reduced in the triple mutant,which often produced elongated conidia with more septa than the wild-type conidia.The triple mutant was blocked in sexual reproduction due to the loss of female fertility.Lack of any MAPKs resulted in an increased sensitivity to various abiotic stress including cell wall,osmotic,oxidative stresses,and phytoalexins,which are likely related to the defects of the triple mutant in environmental adaptation and plant infection.The triple mutant also had increased sensitivity to the biocontrol bacterium Bacillus velezensis and fungus Clonostachys rosea.In co-incubation assays with B.velezensis,the Gpmk1 mgv1 Fghog1 mutant had more severe growth limitation than the wild type and was defective in conidium germination and germ tube growth.In confrontation assays,the triple mutant was defective in defending against mycoparasitic activities of C.rosea and the latter could grow over the mutant but not wild-type F.graminearum.RNA-seq and metabolomics analyses showed that the MAPK triple mutant was altered in the expression of many ATP-binding cassette(ABC)and major facilitator superfamily(MFS)transporter genes and the accumulation of metabolites related to arachidonic acid,linoleic acid,and alpha-linolenic acid metabolisms.Overall,as the first study on mutants deleted of all three MAPKs in fungal pathogens,our results showed that although MAPKs are not essential for growth and asexual reproduction,the Gpmk1 mgv1 Fghog1 triple mutant was blocked in plant infection and sexual reproductions.It also had severe defects in responses to various abiotic stresses and bacterial-or fungal-fungal interactions.展开更多
Plant hormones are important for regulating growth,development,and plant-pathogen interactions.Some of them are inhibitory to growth of fungal pathogens but the underlying mechanism is not clear.In this study,we found...Plant hormones are important for regulating growth,development,and plant-pathogen interactions.Some of them are inhibitory to growth of fungal pathogens but the underlying mechanism is not clear.In this study,we found that hyphal growth of Fusarium graminearum was significantly reduced by high concentrations of IAA and its metabolically stable analogue 2,4-dichlorophenoxyacetic acid(2,4-D).Besides inhibitory effects on growth rate,treatments with 2,4-D also caused significant reduction in conidiation,conidium germination,and germ tube growth.Treatments with 2,4-D had no obvious effect on sexual reproduction but significantly reduced TRI gene expression,toxisome formation,and DON production.More importantly,treatments with 2,4-D were inhibitory to infection structure formation and pathogenesis at concentrations higher than 100μM.The presence of 1000μM 2,4-D almost completely inhibited plant infection and invasive growth.In F.graminearum,2,4-D induced ROS accumulation and FgHog1 activation but reduced the phosphorylation level of Gpmk1 MAP kinase.Metabolomics analysis showed that the accumulation of a number of metabolites such as glycerol and arabitol was increased by 2,4-D treatment in the wild type but not in the Fghog1 mutant.Transformants expressing the dominant active FgPBS2^(S451D T455D) allele were less sensitive to 2,4-D and had elevated levels of intracellular glycerol and arabitol induced by 2,4-D in PH-1.Taken together,our results showed that treatments with 2,4-D interfere with two important MAP kinase pathways and are inhibitory to hyphal growth,DON biosynthesis,and plant infection in F.graminearum.展开更多
基金supported by grants from National Natural Science Foundation of China(no.31772114)to JC,the Natural Science Basic Research Plan in Shaanxi Province of China(no.2020JQ-252)to XZ and grants from USWBSI CI and NSF to JX.
文摘Like other eukaryotes,fungi use MAP kinase(MAPK)pathways to mediate cellular changes responding to external stimuli.In the past two decades,three well-conserved MAP kinase pathways have been characterized in various plant pathogenic fungi for regulating responses and adaptations to a variety of biotic and abiotic stresses encountered during plant infection or survival in nature.The invasive growth(IG)pathway is homologous to the yeast pheromone response and filamentation pathways.In plant pathogens,the IG pathway often is essential for pathogenesis by regulating infection-related morphogenesis,such as appressorium formation,penetration,and invasive growth.The cell wall integrity(CWI)pathway also is important for plant infection although the infection processes it regulates vary among fungal pathogens.Besides its universal function in cell wall integrity,it often plays a minor role in responses to oxidative and cell wall stresses.Both the IG and CWI pathways are involved in regulating known virulence factors as well as effector genes during plant infection and mediating defenses against mycoviruses,bacteria,and other fungi.In contrast,the high osmolarity growth(HOG)pathway is dispensable for virulence in some fungi although it is essential for plant infection in others.It regulates osmoregulation in hyphae and is dispensable for appressorium turgor generation.The HOG pathway also plays a major role for responding to oxidative,heat,and other environmental stresses and is overstimulated by phenylpyrrole fungicides.Moreover,these three MAPK pathways crosstalk and coordinately regulate responses to various biotic and abiotic stresses.The IG and CWI pathways,particularly the latter,also are involved in responding to abiotic stresses to various degrees in different fungal pathogens,and the HOG pathway also plays a role in interactions with other microbes or fungi.Furthermore,some infection processes or stress responses are co-regulated by MAPK pathways with cAMP or Ca^(2+)/CaM signaling.Overall,functions of individual MAP kinase pathways in pathogenesis and stress responses have been well characterized in a number of fungal pathogens,showing the conserved genetic elements with diverged functions,likely by rewiring transcriptional regulatory networks.In the near future,applications of genomics and proteomics approaches will likely lead to better understanding of crosstalk among the MAPKs and with other signaling pathways as well as roles of MAPKs in defense against other microbes(biotic interactions).
基金supported by grants from the National Youth Talent Support Program and National Natural Science Foundation of China(no.31772114)to JC and grants from NSWBSI to JRX。
文摘Mitogen-activated protein kinase(MAPK)cascades are activated by external stimuli and convert signals to cellular changes.Individual MAPKs have been characterized in a number of plant pathogenic fungi for their roles in pathogenesis and responses to biotic or abiotic stresses.However,mutants deleted of all the MAPK genes have not been reported in filamentous fungi.To determine the MAPK-less effects in a fungal pathogen,in this study we generated and characterized mutants deleted of all three MAPK genes in the wheat scab fungus Fusarium graminearum.The Gpmk1 mgv1 Fghog1 triple mutants had severe growth defects and was non-pathogenic.It was defective in infection cushion formation and DON production.Conidiation was reduced in the triple mutant,which often produced elongated conidia with more septa than the wild-type conidia.The triple mutant was blocked in sexual reproduction due to the loss of female fertility.Lack of any MAPKs resulted in an increased sensitivity to various abiotic stress including cell wall,osmotic,oxidative stresses,and phytoalexins,which are likely related to the defects of the triple mutant in environmental adaptation and plant infection.The triple mutant also had increased sensitivity to the biocontrol bacterium Bacillus velezensis and fungus Clonostachys rosea.In co-incubation assays with B.velezensis,the Gpmk1 mgv1 Fghog1 mutant had more severe growth limitation than the wild type and was defective in conidium germination and germ tube growth.In confrontation assays,the triple mutant was defective in defending against mycoparasitic activities of C.rosea and the latter could grow over the mutant but not wild-type F.graminearum.RNA-seq and metabolomics analyses showed that the MAPK triple mutant was altered in the expression of many ATP-binding cassette(ABC)and major facilitator superfamily(MFS)transporter genes and the accumulation of metabolites related to arachidonic acid,linoleic acid,and alpha-linolenic acid metabolisms.Overall,as the first study on mutants deleted of all three MAPKs in fungal pathogens,our results showed that although MAPKs are not essential for growth and asexual reproduction,the Gpmk1 mgv1 Fghog1 triple mutant was blocked in plant infection and sexual reproductions.It also had severe defects in responses to various abiotic stresses and bacterial-or fungal-fungal interactions.
基金supported by grant to Ping Xiang from Shaanxi Provincial Department of Science and Technology(No.2023-JC-QN-0177)grant to Xue Zhang from National Natural Science Foundation of China(No.3210170916)grants to Jin-Rong Xu from NSF and USWBSI.
文摘Plant hormones are important for regulating growth,development,and plant-pathogen interactions.Some of them are inhibitory to growth of fungal pathogens but the underlying mechanism is not clear.In this study,we found that hyphal growth of Fusarium graminearum was significantly reduced by high concentrations of IAA and its metabolically stable analogue 2,4-dichlorophenoxyacetic acid(2,4-D).Besides inhibitory effects on growth rate,treatments with 2,4-D also caused significant reduction in conidiation,conidium germination,and germ tube growth.Treatments with 2,4-D had no obvious effect on sexual reproduction but significantly reduced TRI gene expression,toxisome formation,and DON production.More importantly,treatments with 2,4-D were inhibitory to infection structure formation and pathogenesis at concentrations higher than 100μM.The presence of 1000μM 2,4-D almost completely inhibited plant infection and invasive growth.In F.graminearum,2,4-D induced ROS accumulation and FgHog1 activation but reduced the phosphorylation level of Gpmk1 MAP kinase.Metabolomics analysis showed that the accumulation of a number of metabolites such as glycerol and arabitol was increased by 2,4-D treatment in the wild type but not in the Fghog1 mutant.Transformants expressing the dominant active FgPBS2^(S451D T455D) allele were less sensitive to 2,4-D and had elevated levels of intracellular glycerol and arabitol induced by 2,4-D in PH-1.Taken together,our results showed that treatments with 2,4-D interfere with two important MAP kinase pathways and are inhibitory to hyphal growth,DON biosynthesis,and plant infection in F.graminearum.
