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
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.
