Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways.The transcriptional repressor proteins SUPPRESSOR OF MAX21(SMAX1),SMAX1-like2(SMXL2),and D53...Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways.The transcriptional repressor proteins SUPPRESSOR OF MAX21(SMAX1),SMAX1-like2(SMXL2),and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or byinhibiting the activities of transcription factors.In this study,we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis.We discovered that SMAX1 and SMXL2 with mutations in their ethylene-responsefactor-associated amphiphilic repression(EAR)motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant.SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR4(PIF4)and PIF5 to enhance their protein stability by interacting with phytochrome B(phyB)and suppressing the association of phyB with PIF4 and PIF5.The karrikin-responsive genes were then identified by treatment with GR24ent-ssa,GR24 analog showing karrikin activity.Interestingly,INDOLE-3-ACETIC ACID INDUCIBLE 29(IAA29)expression was repressed by GR24^(ent-5D)streatment in a PIF4-and PIF5-dependent and EARindependent manner,whereas KARRIKIN UPREGULATED F-BOX 1(KUF1)expression was induced in a PIF4-and PIF5-independent and EAR-dependent manner.Furthermore,the non-transcriptional regulatory activity of SMAX1,which is independent of the EAR motif,had a global effect on gene expression.Taken together,these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.展开更多
基金the National Natural Science Foundation of China(32170320,32122012,and 32270327)the Hebei Natural Science Foundation(C2022503003)the Youth Innovation Promotion Association of the Chinese Academy of Sciences(Y2023025).
文摘Karrikins and strigolactones govern plant development and environmental responses through closely related signaling pathways.The transcriptional repressor proteins SUPPRESSOR OF MAX21(SMAX1),SMAX1-like2(SMXL2),and D53-like SMXLs mediate karrikin and strigolactone signaling by directly binding downstream genes or byinhibiting the activities of transcription factors.In this study,we characterized the non-transcriptional regulatory activities of SMXL proteins in Arabidopsis.We discovered that SMAX1 and SMXL2 with mutations in their ethylene-responsefactor-associated amphiphilic repression(EAR)motif had undetectable or weak transcriptional repression activities but still partially rescued the hypocotyl elongation defects and fully reversed the cotyledon epinasty defects of the smax1 smxl2 mutant.SMAX1 and SMXL2 directly interact with PHYTOCHROME INTERACTION FACTOR4(PIF4)and PIF5 to enhance their protein stability by interacting with phytochrome B(phyB)and suppressing the association of phyB with PIF4 and PIF5.The karrikin-responsive genes were then identified by treatment with GR24ent-ssa,GR24 analog showing karrikin activity.Interestingly,INDOLE-3-ACETIC ACID INDUCIBLE 29(IAA29)expression was repressed by GR24^(ent-5D)streatment in a PIF4-and PIF5-dependent and EARindependent manner,whereas KARRIKIN UPREGULATED F-BOX 1(KUF1)expression was induced in a PIF4-and PIF5-independent and EAR-dependent manner.Furthermore,the non-transcriptional regulatory activity of SMAX1,which is independent of the EAR motif,had a global effect on gene expression.Taken together,these results indicate that non-transcriptional regulatory activities of SMAX1 and SMXL2 mediate karrikin-regulated seedling response to red light.
