The phytohormone jasmonates(JAs)regulate plant growth and defense responses.The reproductive organs of flowers are devastated by insect herbivores.However,the molecular mechanisms of floral defense remain largely unkn...The phytohormone jasmonates(JAs)regulate plant growth and defense responses.The reproductive organs of flowers are devastated by insect herbivores.However,the molecular mechanisms of floral defense remain largely unknown.Here,we found that the Arabidopsis JA receptor CORONATINE INSENSITIVE1(COI1)and its substrates JA ZIMdomain(JAZ)repressors,and the mediator subunit MEDIATOR25-based MED25-MYC-MYB(MMM)complexes,including MYC2/3/4/5 and MYB28/29/76,mediated floral defense against the insects Helicoverpa armigera,Spodoptera exigua,and Spodoptera frugiperda.The flower-specific IIIa b HLH factors ABORTED MICROSPORES(AMS)and DYSFUNCTIONAL TAPETUM 1(DYT1)were JAZ-interaction proteins.They interacted with members of the MMM complexes,inhibited the transcriptional activity of MYC2 and MYB28,and repressed floral defense against insects.AMS and DYT1 recruited the flower-specific MYB21/24,and these MYBs interacted with members of MMM complexes,inhibited the MYC2-MYB28 function,and suppressed floral defense against insects.Our study revealed that the JA-COI1-JAZ-MMM pathway mediated flower defense,and the AMS/DYT1-MYB21/24 module antagonized the MMM complexes to repress floral defense against insects.展开更多
The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening sy...The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid （YIH） and yeast-two-hybrid （Y2H） methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions： the CHE-CCA1 promoter interaction by YIH and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key reg- ulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcrip- tional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.展开更多
MED25 has been implicated as a negative regulator of the abscisic acid(ABA)signaling pathway.However,it is unclear whether other Mediator subunits could associate with MED25 to participate in the ABA response.Here,we ...MED25 has been implicated as a negative regulator of the abscisic acid(ABA)signaling pathway.However,it is unclear whether other Mediator subunits could associate with MED25 to participate in the ABA response.Here,we used affinity purification followed by mass spectrometry to uncover Mediator subunits that associate with MED25 in transgenic plants.We found that at least26 Mediator subunits,belonging to the head,middle,tail,and CDK8 kinase modules,were copurified with MED25 in vivo.Interestingly,the tail module subunit MED16 was identified to associate with MED25 under both mock and ABA treatments.We further showed that the disruption of MED16 led to reduced ABA sensitivity compared to the wild type.Transcriptomic analysis revealedthattheexpressionofseveral ABA-responsive genes was significantly lower in med16 than those in wild type.Furthermore,we discovered that MED16 may possibly compete with MED25 to interact with the key transcription factor ABA INSENSITIVE 5(ABI5)to positively regulate ABA signaling.Consistently,med16 and med25 mutants displayed opposite phenotypes in ABA response,cuticle permeability,and differential ABI5-mediated EM1 and EM6 expression.Together,our data indicate that MED16 and MED25 differentially regulate ABA signaling byantagonisticallyaffectingABI5-mediated transcription in Arabidopsis.展开更多
Grain number is a flexible trait and contributes significantly to grain yield.In rice,the zinc finger transcription factor DROUGHT AND SALT TOLERANCE(DST)controls grain number by directly regulating cytokinin oxidase!...Grain number is a flexible trait and contributes significantly to grain yield.In rice,the zinc finger transcription factor DROUGHT AND SALT TOLERANCE(DST)controls grain number by directly regulating cytokinin oxidase!dehydrogenase 2(OsCKX2)expression.Although specific upstream regulators of the DST-OsCKX2 module have been identified,the mechanism employed by DST to regulate the expression of OsCKX2 remains unclear.Here,we demonstrate that DST-interacting protein 1(DIP1),known as Mediator subunit OsMED25,acts as an interacting coactivator of DST.Phenotypic analyses revealed that OsMED25-RNAi and the osmed25 mutant plants exhibited enlarged panicles,with enhanced branching and spikelet number,similar to the dst mutant.Genetic analysis indicated that OsMED25 acts in the same pathway as the DST-OsCKX2 module to regulate spikelet number per panicle.Further biochemical analysis showed that OsMED25 physically interacts with DST at the promoter region of OsCKX2,and then recruits RNA polymerase II(Pol II)to activate OsCKX2 transcription.Thus,OsMED25 was involved in the communication between DST and Pol II general transcriptional machinery to regulate spikelet number.In general,our findings reveal a novel function of OsMED25 in DST-OsCKX2 modulated transcriptional regulation,thus enhancing our un derstanding of the regulatory mechanism underlying DST-OsCKX2-mediated spikelet number.展开更多
Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most asp...Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most aspects of the jasmonate （JA） signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance （ISR） triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid （ABA）, salicylic acid （SA）, gibberellins （GAs）, and auxin （IAA）. MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as ＇master switches＇ that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.展开更多
基金supported by the National Natural Science Foundation of China(32270765)。
文摘The phytohormone jasmonates(JAs)regulate plant growth and defense responses.The reproductive organs of flowers are devastated by insect herbivores.However,the molecular mechanisms of floral defense remain largely unknown.Here,we found that the Arabidopsis JA receptor CORONATINE INSENSITIVE1(COI1)and its substrates JA ZIMdomain(JAZ)repressors,and the mediator subunit MEDIATOR25-based MED25-MYC-MYB(MMM)complexes,including MYC2/3/4/5 and MYB28/29/76,mediated floral defense against the insects Helicoverpa armigera,Spodoptera exigua,and Spodoptera frugiperda.The flower-specific IIIa b HLH factors ABORTED MICROSPORES(AMS)and DYSFUNCTIONAL TAPETUM 1(DYT1)were JAZ-interaction proteins.They interacted with members of the MMM complexes,inhibited the transcriptional activity of MYC2 and MYB28,and repressed floral defense against insects.AMS and DYT1 recruited the flower-specific MYB21/24,and these MYBs interacted with members of MMM complexes,inhibited the MYC2-MYB28 function,and suppressed floral defense against insects.Our study revealed that the JA-COI1-JAZ-MMM pathway mediated flower defense,and the AMS/DYT1-MYB21/24 module antagonized the MMM complexes to repress floral defense against insects.
文摘The activities of transcription factors （TFs） require interactions with specific DNA sequences and other reg- ulatory proteins. To detect such interactions in Arabidopsis, we developed a high-throughput screening system with a Gateway-compatible Gal4-AD-TF library of 1589 Arabidopsis TFs, which can be easily screened by mating-based yeast-one-hybrid （YIH） and yeast-two-hybrid （Y2H） methods. The efficiency of the system was validated by examining two well-characterized TF-DNA and TF-protein interactions： the CHE-CCA1 promoter interaction by YIH and NPR1-TGAs interactions by Y2H. We used this system to identify eight TFs that interact with a Mediator subunit, Med25, a key reg- ulator in JA signaling. We identified five TFs that interacted with the GCC-box cis-element in the promoter of PDF1.2, a downstream gene of Med25. We found that three of these TFs, all from the AP2-EREBP family, interact directly both with Med25 and the GCC-box of PDF1.2, suggesting that Med25 regulates PDF1.2 expression through these three TFs. These results demonstrate that this high-throughput Y1H/Y2H screening system is an efficient tool for studying transcrip- tional regulation networks in Arabidopsis. This system will be available for other Arabidopsis researchers, and thus it provides a vital resource for the Arabidopsis community.
基金supported by the National Natural Science Foundation of China(NSFC 31900238 and NSFC 32070307)to Y.Z.
文摘MED25 has been implicated as a negative regulator of the abscisic acid(ABA)signaling pathway.However,it is unclear whether other Mediator subunits could associate with MED25 to participate in the ABA response.Here,we used affinity purification followed by mass spectrometry to uncover Mediator subunits that associate with MED25 in transgenic plants.We found that at least26 Mediator subunits,belonging to the head,middle,tail,and CDK8 kinase modules,were copurified with MED25 in vivo.Interestingly,the tail module subunit MED16 was identified to associate with MED25 under both mock and ABA treatments.We further showed that the disruption of MED16 led to reduced ABA sensitivity compared to the wild type.Transcriptomic analysis revealedthattheexpressionofseveral ABA-responsive genes was significantly lower in med16 than those in wild type.Furthermore,we discovered that MED16 may possibly compete with MED25 to interact with the key transcription factor ABA INSENSITIVE 5(ABI5)to positively regulate ABA signaling.Consistently,med16 and med25 mutants displayed opposite phenotypes in ABA response,cuticle permeability,and differential ABI5-mediated EM1 and EM6 expression.Together,our data indicate that MED16 and MED25 differentially regulate ABA signaling byantagonisticallyaffectingABI5-mediated transcription in Arabidopsis.
基金supported by the National Key Research and Development Program of China (Grant No. 2019YFD1000300)Agricultural Seed Project of Shandong Province (Grant Nos 2020LZGC005, 2021LZGC0017)+1 种基金the Tai-Shan Scholar Program from Shandong Province (Grant No. tsxk20150901)the K. C. Wong Education Foundation.
文摘Grain number is a flexible trait and contributes significantly to grain yield.In rice,the zinc finger transcription factor DROUGHT AND SALT TOLERANCE(DST)controls grain number by directly regulating cytokinin oxidase!dehydrogenase 2(OsCKX2)expression.Although specific upstream regulators of the DST-OsCKX2 module have been identified,the mechanism employed by DST to regulate the expression of OsCKX2 remains unclear.Here,we demonstrate that DST-interacting protein 1(DIP1),known as Mediator subunit OsMED25,acts as an interacting coactivator of DST.Phenotypic analyses revealed that OsMED25-RNAi and the osmed25 mutant plants exhibited enlarged panicles,with enhanced branching and spikelet number,similar to the dst mutant.Genetic analysis indicated that OsMED25 acts in the same pathway as the DST-OsCKX2 module to regulate spikelet number per panicle.Further biochemical analysis showed that OsMED25 physically interacts with DST at the promoter region of OsCKX2,and then recruits RNA polymerase II(Pol II)to activate OsCKX2 transcription.Thus,OsMED25 was involved in the communication between DST and Pol II general transcriptional machinery to regulate spikelet number.In general,our findings reveal a novel function of OsMED25 in DST-OsCKX2 modulated transcriptional regulation,thus enhancing our un derstanding of the regulatory mechanism underlying DST-OsCKX2-mediated spikelet number.
文摘Jasmonates （JAs） are plant hormones with essential roles in plant defense and development. The basic- helix-loop-helix （bHLH） transcription factor （TF） MYC2 has recently emerged as a master regulator of most aspects of the jasmonate （JA） signaling pathway in Arabidopsis. MYC2 coordinates JA-mediated defense responses by antagonistically regulating two different branches of the JA signaling pathway that determine resistance to pests and pathogens, respectively. MYC2 is required for induced systemic resistance （ISR） triggered by beneficial soil microbes while MYC2 function is targeted by pathogens during effector-mediated suppression of innate immunity in roots. Another notable function of MYC2 is the regulation of crosstalk between the signaling pathways of JA and those of other phytohormones such as abscisic acid （ABA）, salicylic acid （SA）, gibberellins （GAs）, and auxin （IAA）. MYC2 also regulates interactions between JA signaling and light, phytochrome signaling, and the circadian clock, MYC2 is involved in JA-regulated plant development, lateral and adventitious root formation, flowering time, and shade avoidance syndrome. Related bHLH TFs MYC3 and MYC4 also regulate both overlapping and distinct MYC2-regulated functions in Arabidopsis while MYC2 orthologs act as ＇master switches＇ that regulate JA-mediated biosynthesis of secondary metabolites. Here, we briefly review recent studies that revealed mechanistic new insights into the mode of action of this versatile TF.
