In this study,we synthesized a series of ABA-type vitrimers by crosslinking the short A moieties of precursors with a bifunctional crosslinker and evaporating the small molecular byproduct.The vitrimer samples thus pr...In this study,we synthesized a series of ABA-type vitrimers by crosslinking the short A moieties of precursors with a bifunctional crosslinker and evaporating the small molecular byproduct.The vitrimer samples thus prepared exhibit linear viscoelasticity dependent on the length of A moiety as well as the content of the crosslinks.When the average number of A monomers per end moiety m=1.1,the crosslinker can only extend the chain but not crosslink the chain.When m becomes 2.8 or higher,introducing a crosslinker first leads to the gelation,whereas excess in crosslinker molecules leads opening of the crosslinking sites and accordingly reentry into the sol regime.Surprisingly,a further increase in the length of the A moieties increases the relaxation time much weaker than the exponential increase seen for the physically crosslinked ABAtype ionomers.We attribute this difference to the distinct relaxation mechanisms:the relaxation of the vitrimer samples is based on relatively independent exchange reactions,which contrasts with the ABA-type ionomers that relax through the collective hopping of connected ionic groups from one ion aggregate to another.展开更多
The abscisic acid （ABA） signaling pathway is regulated by clade A type 2C protein phosphatases （PP2CAs） in plants. In the presence of ABA, PP2Cs release stress/ABA-activated protein kinases by binding to ABA-bound...The abscisic acid （ABA） signaling pathway is regulated by clade A type 2C protein phosphatases （PP2CAs） in plants. In the presence of ABA, PP2Cs release stress/ABA-activated protein kinases by binding to ABA-bound receptors （PYL/RCARs） for activation. Although the wedging tryptophan in PP2Cs is critical in the interaction with PYL/RCARs in Arabidopsis and rice, it remains elusive as to how other interface regions are involved in the interaction. Here, we report the identification of a conserved region on PP2Cs, termed the VxG4ФL motif, which modulates the interaction with PYL/RCARs through its second and fourth residues. The effects of the second and fourth residues on the interaction of OsPP2CS0 with several OsPYIJRCAR proteins were investigated by systematic mutagenesis. One OsPP2C50 mutant, VFGML （＂FM＂） mutant, lowered the affinity to OsPYL/RCAR3 by Ф15-fold in comparison with the wUd-type. Compar- ison of the crystal structures of wild-type OsPP2C50：ABA：OsPYI./RCAR3 with those composed of FM mutant revealed local conformational changes near the VxGФL motif, further supported by hydrogen-deute- rium exchange mass spectrometry. In rice protoplasts, ABA signaling was altered by mutations in the VxGФL motif. Transgenic Arabidopsis plants overexpressing OsPP2C50 and OsPP2C5OFM showed altered ABA sensitivity. Taken together, the VxGФL motif of PP2Cs appears to modulate the affinity of PP2Cs with PYL/RCARs and thus likely to alter the ABA signaling, leading to the differential sensitivity to ABA in planta.展开更多
基金financially supported by the National Natural Science Foundation of China(Nos.22173095 and 52103021)。
文摘In this study,we synthesized a series of ABA-type vitrimers by crosslinking the short A moieties of precursors with a bifunctional crosslinker and evaporating the small molecular byproduct.The vitrimer samples thus prepared exhibit linear viscoelasticity dependent on the length of A moiety as well as the content of the crosslinks.When the average number of A monomers per end moiety m=1.1,the crosslinker can only extend the chain but not crosslink the chain.When m becomes 2.8 or higher,introducing a crosslinker first leads to the gelation,whereas excess in crosslinker molecules leads opening of the crosslinking sites and accordingly reentry into the sol regime.Surprisingly,a further increase in the length of the A moieties increases the relaxation time much weaker than the exponential increase seen for the physically crosslinked ABAtype ionomers.We attribute this difference to the distinct relaxation mechanisms:the relaxation of the vitrimer samples is based on relatively independent exchange reactions,which contrasts with the ABA-type ionomers that relax through the collective hopping of connected ionic groups from one ion aggregate to another.
文摘The abscisic acid （ABA） signaling pathway is regulated by clade A type 2C protein phosphatases （PP2CAs） in plants. In the presence of ABA, PP2Cs release stress/ABA-activated protein kinases by binding to ABA-bound receptors （PYL/RCARs） for activation. Although the wedging tryptophan in PP2Cs is critical in the interaction with PYL/RCARs in Arabidopsis and rice, it remains elusive as to how other interface regions are involved in the interaction. Here, we report the identification of a conserved region on PP2Cs, termed the VxG4ФL motif, which modulates the interaction with PYL/RCARs through its second and fourth residues. The effects of the second and fourth residues on the interaction of OsPP2CS0 with several OsPYIJRCAR proteins were investigated by systematic mutagenesis. One OsPP2C50 mutant, VFGML （＂FM＂） mutant, lowered the affinity to OsPYL/RCAR3 by Ф15-fold in comparison with the wUd-type. Compar- ison of the crystal structures of wild-type OsPP2C50：ABA：OsPYI./RCAR3 with those composed of FM mutant revealed local conformational changes near the VxGФL motif, further supported by hydrogen-deute- rium exchange mass spectrometry. In rice protoplasts, ABA signaling was altered by mutations in the VxGФL motif. Transgenic Arabidopsis plants overexpressing OsPP2C50 and OsPP2C5OFM showed altered ABA sensitivity. Taken together, the VxGФL motif of PP2Cs appears to modulate the affinity of PP2Cs with PYL/RCARs and thus likely to alter the ABA signaling, leading to the differential sensitivity to ABA in planta.
