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
ETHYLENE INSENSITIVE2(EIN2)is a key component of ethylene signaling whose activity is inhibited upon phosphorylation of Ser^(645) and Ser^(924) by the Raf-like CONSTITUTIVE TRIPLE-RESPONSE 1(CTR1)in the absence of eth...ETHYLENE INSENSITIVE2(EIN2)is a key component of ethylene signaling whose activity is inhibited upon phosphorylation of Ser^(645) and Ser^(924) by the Raf-like CONSTITUTIVE TRIPLE-RESPONSE 1(CTR1)in the absence of ethylene.Ethylene prevents CTR1 activity and thus EIN2^(Ser645/Ser924) phosphorylation,and subcellular trafficking of a proteolytically cleaved EIN2 C terminus(EIN2-C)from the endoplasmic reticulum to the nucleus and processing bodies triggers ethylene signaling.Here,we report an unexpected complexity of EIN2-activated ethylene signaling.EIN2 activation in part requires ethylene in the absence of CTR1-mediated negative regulation.The ein2 mutant was complemented by the transgenes encoding EIN2,EIN2 variants with mutations that either prevent or mimic Ser^(645)/Ser^(924) phosphorylation,or EIN2-C;and all the transgenic lines carrying these EIN2-derived transgenes responded to ethylene.Furthermore,we found that the fluorescence protein-tagged EIN2 and its variants were affected little by ethylene and exhibited similar subcellular distribution patterns:in the cytosolic particles and nuclear speckles.Of note,the subcellular localization patterns of EIN2 proteins fused with a fluorescence protein either at the N or C terminus were similar,whereas EIN2-C-YFP was primarily observed in the cytosol but not in the nucleus.Western blots and mass spectrum analyses suggested a high complexity of EIN2,which is likely proteolytically processed into multiple fragments.Our results suggested a nuclear localization of the full-length EIN2,weak association of the EIN2^(Ser645/Ser924) phosphorylation status and ethylene signaling,and the complexity of ethylene signaling caused by EIN2 and its proteolytic products in different subcellular compartments.We propose an alternative model to explain EIN2-activated ethylene signaling.展开更多
The nitric oxide （NO）-deficient mutant nosllnoal exhibited an early leaf senescence phenotype. ETHY- LENE INSENSITIVE 2 （EIN2） was previously reported to function as a positive regulator of ethylene- induced senes...The nitric oxide （NO）-deficient mutant nosllnoal exhibited an early leaf senescence phenotype. ETHY- LENE INSENSITIVE 2 （EIN2） was previously reported to function as a positive regulator of ethylene- induced senescence. The aim of this study was to address the question of how NO interacts with ethylene to regulate leaf senescence by characterizing the double mutant ein2-1 nosllnoal （Arabidopsis thaliana）. Double mutant analysis revealed that the nosllnoal-mediated, dark-induced early senescence phenotype was suppressed by mutations in EIN2, suggesting that EIN2 is involved in nitric oxide signaling in the regulation of leaf senescence. The results showed that chlorophyll degradation in the double mutant leaves was significantly delayed. In addition, nosllnoal-mediated impairment in photochemical efficiency and integrity of thylakoid membranes was reverted by EIN2 mutations. The rapid upregulation of the known senescence marker genes in the nosl/noal mutant was severely inhibited in the double mutant during leaf senescence. Interestingly, the response of dark-grown nosl/noal mutant seedlings to ethylene was similar to that of wild type seedlings. Taken together, our findings suggest that EIN2 is involved in the regulation of early leaf senescence caused by NO deficiency, but NO deficiency caused by NOSIlNOA1 mutations does not affect ethylene signaling.展开更多
The endosperm plays essential roles in embryogenesis and seed germination and provides abundant resources for human food and industrial products. Identification of genes regulating the development of the endosperm and...The endosperm plays essential roles in embryogenesis and seed germination and provides abundant resources for human food and industrial products. Identification of genes regulating the development of the endosperm and elucidation of their functions is of great importance for maize genetics and breeding. This study showed that the genespecific imprinted gene, ETHYLENE-INSENSITIVE 2-like(EIN2-like), is maternally expressed in both endosperm and embryo. The maternally expressed pattern was maintained throughout later seed developmental stages. Bisulfite sequencing using DNA obtained from hybrid endosperm tissues showed that the upstream regions of the alleles of EIN2-like were highly methylated at symmetrical sites(CG and CHG). A differentially methylated region in the upstream part of the maternal allele of EIN2-like was identified and found to be hypomethylated. Expression analysis showed that EIN2-like was highly expressed in the maize endosperm as well as at different stages of cell differentiation(8–12 days after pollination) in the hybrid endosperm. These results suggest that the maternally expressed gene EIN2-like may play crucial roles in the regulation of seed development.展开更多
Plant cells in damaged tissue can be reprogrammed to acquire pluripotency and induce callus formation.However,in the aboveground organs of many species,somatic cells that are distal to the wound site become less sensi...Plant cells in damaged tissue can be reprogrammed to acquire pluripotency and induce callus formation.However,in the aboveground organs of many species,somatic cells that are distal to the wound site become less sensitive to auxin-induced callus formation,suggesting the existence of repressive regulatory mechanisms that are largely unknown.Here we reveal that submergence-induced ethylene signals promote callus formation by releasing post-transcriptional silencing of auxin receptor transcripts in non-wounded regions.We determined that short-term submergence of intact seedlings induces auxin-mediated cell dedifferentiation across the entirety of Arabidopsis thaliana explants.The constitutive triple response 1-1(ctr1-1)mutation induced callus formation in explants without submergence,suggesting that ethylene facilitates cell dedifferentiation.We show that ETHYLENE-INSENSITIVE 2(EIN2)post-transcriptionally regulates the abundance of transcripts for auxin receptor genes by facilitating microRNA393 degradation.Submergence-induced calli in non-wounded regions were suitable for shoot regeneration,similar to those near the wound site.We also observed submergence-promoted callus formation in Chinese cabbage(Brassica rapa),indicating that this may be a conserved mechanism in other species.Our study identifies previously unknown regulatory mechanisms by which ethylene promotes cell dedifferentiation and provides a new approach for boosting callus induction efficiency in shoot explants.展开更多
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 the National Natural Science Foundation of China(31570277 and 31770302)Chinese Academy of Sciences(XDB27030208).
文摘ETHYLENE INSENSITIVE2(EIN2)is a key component of ethylene signaling whose activity is inhibited upon phosphorylation of Ser^(645) and Ser^(924) by the Raf-like CONSTITUTIVE TRIPLE-RESPONSE 1(CTR1)in the absence of ethylene.Ethylene prevents CTR1 activity and thus EIN2^(Ser645/Ser924) phosphorylation,and subcellular trafficking of a proteolytically cleaved EIN2 C terminus(EIN2-C)from the endoplasmic reticulum to the nucleus and processing bodies triggers ethylene signaling.Here,we report an unexpected complexity of EIN2-activated ethylene signaling.EIN2 activation in part requires ethylene in the absence of CTR1-mediated negative regulation.The ein2 mutant was complemented by the transgenes encoding EIN2,EIN2 variants with mutations that either prevent or mimic Ser^(645)/Ser^(924) phosphorylation,or EIN2-C;and all the transgenic lines carrying these EIN2-derived transgenes responded to ethylene.Furthermore,we found that the fluorescence protein-tagged EIN2 and its variants were affected little by ethylene and exhibited similar subcellular distribution patterns:in the cytosolic particles and nuclear speckles.Of note,the subcellular localization patterns of EIN2 proteins fused with a fluorescence protein either at the N or C terminus were similar,whereas EIN2-C-YFP was primarily observed in the cytosol but not in the nucleus.Western blots and mass spectrum analyses suggested a high complexity of EIN2,which is likely proteolytically processed into multiple fragments.Our results suggested a nuclear localization of the full-length EIN2,weak association of the EIN2^(Ser645/Ser924) phosphorylation status and ethylene signaling,and the complexity of ethylene signaling caused by EIN2 and its proteolytic products in different subcellular compartments.We propose an alternative model to explain EIN2-activated ethylene signaling.
基金supported by the National Natural Science Foundation of China (31170244 and 30770198)
文摘The nitric oxide （NO）-deficient mutant nosllnoal exhibited an early leaf senescence phenotype. ETHY- LENE INSENSITIVE 2 （EIN2） was previously reported to function as a positive regulator of ethylene- induced senescence. The aim of this study was to address the question of how NO interacts with ethylene to regulate leaf senescence by characterizing the double mutant ein2-1 nosllnoal （Arabidopsis thaliana）. Double mutant analysis revealed that the nosllnoal-mediated, dark-induced early senescence phenotype was suppressed by mutations in EIN2, suggesting that EIN2 is involved in nitric oxide signaling in the regulation of leaf senescence. The results showed that chlorophyll degradation in the double mutant leaves was significantly delayed. In addition, nosllnoal-mediated impairment in photochemical efficiency and integrity of thylakoid membranes was reverted by EIN2 mutations. The rapid upregulation of the known senescence marker genes in the nosl/noal mutant was severely inhibited in the double mutant during leaf senescence. Interestingly, the response of dark-grown nosl/noal mutant seedlings to ethylene was similar to that of wild type seedlings. Taken together, our findings suggest that EIN2 is involved in the regulation of early leaf senescence caused by NO deficiency, but NO deficiency caused by NOSIlNOA1 mutations does not affect ethylene signaling.
基金the Major Research Projects of Chongqing (CSTC2016shms-ztzx80013, CSTC2016shms-ztzx80016) for financial support
文摘The endosperm plays essential roles in embryogenesis and seed germination and provides abundant resources for human food and industrial products. Identification of genes regulating the development of the endosperm and elucidation of their functions is of great importance for maize genetics and breeding. This study showed that the genespecific imprinted gene, ETHYLENE-INSENSITIVE 2-like(EIN2-like), is maternally expressed in both endosperm and embryo. The maternally expressed pattern was maintained throughout later seed developmental stages. Bisulfite sequencing using DNA obtained from hybrid endosperm tissues showed that the upstream regions of the alleles of EIN2-like were highly methylated at symmetrical sites(CG and CHG). A differentially methylated region in the upstream part of the maternal allele of EIN2-like was identified and found to be hypomethylated. Expression analysis showed that EIN2-like was highly expressed in the maize endosperm as well as at different stages of cell differentiation(8–12 days after pollination) in the hybrid endosperm. These results suggest that the maternally expressed gene EIN2-like may play crucial roles in the regulation of seed development.
基金This work was supported by the Basic Research Program provided by the National Research Foundation of Korea(NRF-2019R1C1C1002045 and NRF-2021R1A2C4002413)the New Breeding Technologies Development Program(project PJ0165302022)provided by the Rural Development Administration of Korea,and the KRIBB Research Initiative Program(KGM5372221).
文摘Plant cells in damaged tissue can be reprogrammed to acquire pluripotency and induce callus formation.However,in the aboveground organs of many species,somatic cells that are distal to the wound site become less sensitive to auxin-induced callus formation,suggesting the existence of repressive regulatory mechanisms that are largely unknown.Here we reveal that submergence-induced ethylene signals promote callus formation by releasing post-transcriptional silencing of auxin receptor transcripts in non-wounded regions.We determined that short-term submergence of intact seedlings induces auxin-mediated cell dedifferentiation across the entirety of Arabidopsis thaliana explants.The constitutive triple response 1-1(ctr1-1)mutation induced callus formation in explants without submergence,suggesting that ethylene facilitates cell dedifferentiation.We show that ETHYLENE-INSENSITIVE 2(EIN2)post-transcriptionally regulates the abundance of transcripts for auxin receptor genes by facilitating microRNA393 degradation.Submergence-induced calli in non-wounded regions were suitable for shoot regeneration,similar to those near the wound site.We also observed submergence-promoted callus formation in Chinese cabbage(Brassica rapa),indicating that this may be a conserved mechanism in other species.Our study identifies previously unknown regulatory mechanisms by which ethylene promotes cell dedifferentiation and provides a new approach for boosting callus induction efficiency in shoot explants.
