Mitogen-activated protein kinases （MAPKs） are involved in the regulation of plant growth, development and responses to a wide variety of stimuli. In a conditional gain-of-function transgenic system, the activation o...Mitogen-activated protein kinases （MAPKs） are involved in the regulation of plant growth, development and responses to a wide variety of stimuli. In a conditional gain-of-function transgenic system, the activation of AtMEKS, a MAPK kinase, can in turn activate endogenous AtMAPK3 and AtMAPK6, and can lead to a striking increase in ethylene production and induce hypersensitive response （HR）-like cell death in Arabidopsis. However, the role of the increased ethylene production in regulating this HR-like cell death remains unknown. Using Arabidopsis transgenic plants that express AtMEK5DD, an active mutant of AtMEK5 that is under the control of a steroid-inducible promoter, we tested the contribution of ethylene to cell death. We found that ethylene biosynthesis occurs before cell death. Cell death was delayed by inhibiting AtMEKS-induced ethylene production using inhibitors ofACC-synthases, ACC- oxidases or ethylene receptors. In the mutants AtMEK5^DD/etrl-1 and AtMEK5^DD/ein2-1, both of which showed insensitivity to ethylene, the expression ofAtMEK5DD protein, activity of AtMAPK3 and AtMAPK6, and ethylene produc- tion were the same as those seen in AtMEK5^DD transgenic plants, but cell death was also delayed. These data suggest that ethylene signaling perception is required to accelerate cell death that is induced by AtMEK5 activation.展开更多
AtMEK5 DD is an active mutant of AtMEK5, a MAP kinase kinase in Arabidopsis. Induction of AtMEK5 DD expression in transgenic plants leads to activation of 44 and 48 kD MAPKs and causes a rapid cell death. To compare t...AtMEK5 DD is an active mutant of AtMEK5, a MAP kinase kinase in Arabidopsis. Induction of AtMEK5 DD expression in transgenic plants leads to activation of 44 and 48 kD MAPKs and causes a rapid cell death. To compare the cell death induced by the expression of AtMEK5 DD with the HR-cell death induced by avirulence pathogen infection, we analyzed the activation of downstream MAP Kinase and induction of PR genes expression in permanent transgenic Arabidopsis plants. In-gel kinase activity assay revealed that the infection of Pseudomonas syringae DC3000 harboring Avr Rpt2 gene also lead to activation of 44 and 48 kD MAPKs. PAL, PR1 and PR5 were strongly induced in plants undergo- ing HR-cell death caused by the infection of P. syringae DC3000, while only the expression of PR5 was strongly in- duced in transgenic plants expressing AtMEK5 DD protein. NahG protein in AtMEK5 ×NahG plants cannot suppress DD the cell death induced by AtMEK5 . And AtMEK5 DD DD pro- tein expressed AtMEK5 ×NahG plants showed no signifi- DD cant change in salicylic acid (SA) level. All these suggest that the cell death induced by the activation of AtMEK5 is sali- cylic acid-independent.展开更多
基金This work was supported by National Basic Research Program of China （Grant No. 2003CB114304）, the National Natural Science Foundation of China （Grant Nos. 30421002, 30770203, and 30370140）, NCET 04-0131 and the Fok Ying Tung Education Foundation （Grant No. 91022） to D Ren, and the National Natural Science Foundation of China （Grant No. 30770128） to G Liu.
文摘Mitogen-activated protein kinases （MAPKs） are involved in the regulation of plant growth, development and responses to a wide variety of stimuli. In a conditional gain-of-function transgenic system, the activation of AtMEKS, a MAPK kinase, can in turn activate endogenous AtMAPK3 and AtMAPK6, and can lead to a striking increase in ethylene production and induce hypersensitive response （HR）-like cell death in Arabidopsis. However, the role of the increased ethylene production in regulating this HR-like cell death remains unknown. Using Arabidopsis transgenic plants that express AtMEK5DD, an active mutant of AtMEK5 that is under the control of a steroid-inducible promoter, we tested the contribution of ethylene to cell death. We found that ethylene biosynthesis occurs before cell death. Cell death was delayed by inhibiting AtMEKS-induced ethylene production using inhibitors ofACC-synthases, ACC- oxidases or ethylene receptors. In the mutants AtMEK5^DD/etrl-1 and AtMEK5^DD/ein2-1, both of which showed insensitivity to ethylene, the expression ofAtMEK5DD protein, activity of AtMAPK3 and AtMAPK6, and ethylene produc- tion were the same as those seen in AtMEK5^DD transgenic plants, but cell death was also delayed. These data suggest that ethylene signaling perception is required to accelerate cell death that is induced by AtMEK5 activation.
文摘AtMEK5 DD is an active mutant of AtMEK5, a MAP kinase kinase in Arabidopsis. Induction of AtMEK5 DD expression in transgenic plants leads to activation of 44 and 48 kD MAPKs and causes a rapid cell death. To compare the cell death induced by the expression of AtMEK5 DD with the HR-cell death induced by avirulence pathogen infection, we analyzed the activation of downstream MAP Kinase and induction of PR genes expression in permanent transgenic Arabidopsis plants. In-gel kinase activity assay revealed that the infection of Pseudomonas syringae DC3000 harboring Avr Rpt2 gene also lead to activation of 44 and 48 kD MAPKs. PAL, PR1 and PR5 were strongly induced in plants undergo- ing HR-cell death caused by the infection of P. syringae DC3000, while only the expression of PR5 was strongly in- duced in transgenic plants expressing AtMEK5 DD protein. NahG protein in AtMEK5 ×NahG plants cannot suppress DD the cell death induced by AtMEK5 . And AtMEK5 DD DD pro- tein expressed AtMEK5 ×NahG plants showed no signifi- DD cant change in salicylic acid (SA) level. All these suggest that the cell death induced by the activation of AtMEK5 is sali- cylic acid-independent.
