MPK6对1-氨基环丙烷-1-羧酸合酶的活化诱导拟南芥乙烯的生物合成
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Field: Plant & Animal Science
Article Title: Phosphorylation of 1-aminocyclopropane-1-carboxylic acid synthase by MPK6, a stress-responsive mitogen-activated protein kinase, induces ethylene biosynthesis in Arabidopsis
Authors: Liu, YD;Zhang, SQ
Journal: PLANT CELL
Volume: 16 (12)
Q：Why do you think your paper is highly cited?
A：Mitogen-activated protein kinase (MAPK) cascades play vital roles in signaling cellular responses to external and endogenous stimuli in eukaryotes. It has been more than 10 years since the cloning and identification of the first plant MAPK (Duerr, B.; Gawienowski, M.; Ropp, T.; and Jacobs, T. 1993. Plant Cell 5: 87-96; Jonak, C.; PṬ A.; B?, L.; Hirt, H.; and Heberle-Bors, E. 1993. Plant J. 3: 611-617). In the fully sequenced Arabidopsis genome, there are 20 MAPKs, 10 MAPKKs, and more than 60 MAPKKKs (MAPK Group. 2002. Trends Plant Sci. 7, 301-308). Based on gain-of-function and loss-of-function analyses, plant MAPKs were shown to be involved in plant growth, development, and response to stress stimuli. However, the underlying mechanisms are unknown because of the lack of information about plant MAPK substrates. In this paper, we described the first plant MAPK substrate, 1-aminocyclopropane-1-carboxylic acid synthase (ACS), which is the rate-limiting enzyme of ethylene biosynthesis. Previously, we found that stress-responsive MAPK cascade (NtMEK2-SIPK/WIPK) regulates the biosynthesis of ethylene, also known as plant stress hormone (Kim, C.Y.; Liu, Y.; Thorne, E.T.; Yang, H., Fukushig, H.; Gassmann, W.; Hildebrand, D.; Sharp, R.E.; and Zhang, S. 2003. Plant Cell 15: 2707-2718.). In this paper, we demonstrated that phosphorylation of ACS2 and ACS6 by Arabidopsis MPK6, the tobacco SIPK ortholog, stabilizes the ACS protein, resulting in elevated levels of cellular ACS activity and ethylene production. The identification of the first plant MAPK substrate in this report reveals one mechanism by which MPK6 regulates plant stress response. Equally important, this study uncovers a signaling pathway that modulates the biosynthesis of ethylene, an important plant hormone.
Q： Does it describe a new discovery or new methodology that's useful to others?
A：ACS is an enzyme with extremely high specific activity and its protein level is very low in plant cells even at induced state. Making things even more difficult, the molecular weight of ACS is similar to that of the large subunit of Rubisco, the most abundant protein in plants. These make it very difficult to visualize the ACS protein from green plant tissues by immunoblot analysis. In this paper, we described the immune-complex ACS assay, which is an ACS activity assay coupled to the immunoprecipitation with a member-specific ACS antibody. By taking advantage of the specificity of a member-specific antibody and the high specific activity of ACS enzyme, this method allows the detection of a specific ACS member in plant cells. In Arabidopsis, ACS is encoded by a small gene family with at least nine different members.
Q： Could you summarize the significance of your paper in layman's terms?
A：Ethylene, a gaseous plant hormone, plays vital roles in plant growth, development, and response to stress. Recent genetic studies revealed a number of important signaling components in the pathways downstream of ethylene. As Dr. Hans Kende pointed out, "Ethylene-regulated processes are mostly initiated by an increase in ethylene synthesis. Ethylene synthesis is under the control of environmental and/or endogenous signals. Thus, to understand ethylene responses, it will be necessary to identify the exogenous and endogenous factors that control ethylene synthesis and to elucidate the signal transduction pathways that lead to an induction of ethylene biosynthesis (Kende, H. 2001. Plant Physiol. 125: 81-84)." This paper revealed one such pathway.
Q： How did you become involved in this research?
A：The major discovery in this paper is a result of good detective work. We first noticed that selected lines of the gain-of-function NtMEK2 transgenic tobacco plants showed ethylene-induced morphology. By following this phenotype, we determined how MAPK activation induced ethylene biosynthesis. In collaboration with Dr. Robert Sharp's lab (Division of Plant Sciences, University of Missouri-Columbia), we first demonstrated that the ethylene production is greatly enhanced after the activation of SIPK/WIPK, the two downstream MAPKs of NtMEK2. By following the biosynthetic enzymes in the ethylene biosynthetic pathway, we found that a subset of ACS isoforms can be directly phosphorylated by MPK6. The phosphorylation stabilizes the ACS protein and leads to ethylene induction.
Shuqun Zhang
Associate Professor
Department of Biochemistry
University of Missouri-Columbia
Columbia, MO, USA
领域：动植物科学
文章标题：一种应激激活的丝裂原活化的蛋白激酶——MPK6对1-氨基环丙烷-1-羧酸合酶的活化诱导了拟南芥乙烯的生物合成。
作者： Liu, YD;Zhang, SQ
杂志：植物细胞
卷：16（12）
问：为什么你认为自己的论文的引用率很高？
答：丝裂原活化的蛋白激酶（MAPK）级联反应是真核细胞受到外源性和内源性刺激时产生的一种极其重要的反应。自从第一个植物MAPK被成功分离和鉴定以来已经有十几年了(Duerr, B.; Gawienowski, M.; Ropp, T.; and Jacobs, T. 1993. Plant Cell 5: 87-96; Jonak, C.; P? A.; B?, L.; Hirt, H.; and Heberle-Bors, E. 1993. Plant J. 3: 611-617)。全基因组测序后发现拟南芥包含20种MAPKs亚型、10种MAPKKs亚型和60多种MAPKKKs亚型 (MAPK Group. 2002. Trends Plant Sci. 7, 301-308)。通过功能获得和功能缺失分析发现植物MAPKs和植物生长、发育和应激反应密切相关。但是这种相关性背后的机制却由于缺乏植物MAPK底物的信息而至今不明。在这篇论文中，我们描述了第一个植物MAPK的底物，1-氨基环丙烷-1-羧酸（ACS）——乙烯生物合成的限速酶。以前我们发现，与熟知的植物应激激素一样，应激引起的MAPK级联反能够应调节乙烯的生物合成(Kim, C.Y.; Liu, Y.; Thorne, E.T.; Yang, H., Fukushig, H.; Gassmann, W.; Hildebrand, D.; Sharp, R.E.; and Zhang, S. 2003. Plant Cell 15: 2707-2718)。这篇论文中，我们证实了与烟草SIPK直系同源的拟南芥MPK6磷酸化ACS2和ACS6后，使ACS蛋白稳定性增强，最终导致细胞内ACS的活性水平升高而产生更多的乙烯。该论文通过对第一个植物MAPK底物的鉴定揭示了MPK6调节植物应激反应的机制。同样重要的是，该研究发现了一个调节乙烯生物合成的信号通路，以及一个重要的植物激素。
问：这篇论文是否描述了一种可以推广的新发现或者新方法？
答：ACS是一种特异性和活性都非常高的酶，在植物细胞内甚至在在被诱导的状态下其表达水平也非常低。更为不利的是ACS的分子量和植物中含量最高的蛋白——Rubisco的大亚基相当。这些因素导致了在免疫印迹实验中很难在绿色植物组织中看到ACS蛋白。这篇论文中，我们应用了免疫复合物ACS测定法，这是一种ACS活性检测和以膜特异性的ACS抗体的免疫沉淀相结合的检测方法。该方法结合了膜ACS抗体的特异性和ACS的高酶活性，能够检测到植物细胞特异性的ACS家族蛋白。在拟南芥内，ACS由一个小的至少有9个不同的基因成员组成的一个基因家族所编码。
问：你能不能用通俗的语言总结一下您这篇论文的意义？
答：作为一种植物的气体激素，乙烯在植物生长，发育以及应激反应中起重要作用。最近，遗传学的研究者们发现了乙烯信号通路下游大量重要的信号元件。正如Hans Kende 博士所指出的那样，乙烯合成的增加极有可能是乙烯调节过程的启动因素。因为乙烯的合成是受环境信号和/或内源性信号所调控的，所以有必要对这些调控乙烯合成的外源性和内源性因子以及诱导乙烯生物合成的信号通路进行鉴定(Kende, H. 2001. Plant Physiol. 125: 81-84)。我们的这篇论文就发现了能诱导乙烯生物合成的信号通路之一。
问：您是怎样开始介入这项研究的？
答：这篇论文主要的发现源于探索性的工作。首先我们注意到被选择的获得功能的NtMEK2转基因烟草品系具有乙烯诱导的形态特征。然后我们就针对这种表型进行研究，最终发现了MAPK的活化是如何诱导乙烯的生物合成的。与Robert Sharp's 博士（哥伦比亚密苏里大学，植物科学部）合作，我们第一次证明了NtMEK2下游的两个MAPKs——SIPK/WIPK的活化极大的增强了乙烯的合成。对乙烯合成通路中生物合成酶的深入研究表明MPK6能够直接磷酸化ACS的不同亚型。磷酸化的ACS蛋白的稳定性增强最终诱导了乙烯合成！
编辑：西门吹血
Article Title: Phosphorylation of 1-aminocyclopropane-1-carboxylic acid synthase by MPK6, a stress-responsive mitogen-activated protein kinase, induces ethylene biosynthesis in Arabidopsis
Authors: Liu, YD;Zhang, SQ
Journal: PLANT CELL
Volume: 16 (12)
Q：Why do you think your paper is highly cited?
A：Mitogen-activated protein kinase (MAPK) cascades play vital roles in signaling cellular responses to external and endogenous stimuli in eukaryotes. It has been more than 10 years since the cloning and identification of the first plant MAPK (Duerr, B.; Gawienowski, M.; Ropp, T.; and Jacobs, T. 1993. Plant Cell 5: 87-96; Jonak, C.; PṬ A.; B?, L.; Hirt, H.; and Heberle-Bors, E. 1993. Plant J. 3: 611-617). In the fully sequenced Arabidopsis genome, there are 20 MAPKs, 10 MAPKKs, and more than 60 MAPKKKs (MAPK Group. 2002. Trends Plant Sci. 7, 301-308). Based on gain-of-function and loss-of-function analyses, plant MAPKs were shown to be involved in plant growth, development, and response to stress stimuli. However, the underlying mechanisms are unknown because of the lack of information about plant MAPK substrates. In this paper, we described the first plant MAPK substrate, 1-aminocyclopropane-1-carboxylic acid synthase (ACS), which is the rate-limiting enzyme of ethylene biosynthesis. Previously, we found that stress-responsive MAPK cascade (NtMEK2-SIPK/WIPK) regulates the biosynthesis of ethylene, also known as plant stress hormone (Kim, C.Y.; Liu, Y.; Thorne, E.T.; Yang, H., Fukushig, H.; Gassmann, W.; Hildebrand, D.; Sharp, R.E.; and Zhang, S. 2003. Plant Cell 15: 2707-2718.). In this paper, we demonstrated that phosphorylation of ACS2 and ACS6 by Arabidopsis MPK6, the tobacco SIPK ortholog, stabilizes the ACS protein, resulting in elevated levels of cellular ACS activity and ethylene production. The identification of the first plant MAPK substrate in this report reveals one mechanism by which MPK6 regulates plant stress response. Equally important, this study uncovers a signaling pathway that modulates the biosynthesis of ethylene, an important plant hormone.
Q： Does it describe a new discovery or new methodology that's useful to others?
A：ACS is an enzyme with extremely high specific activity and its protein level is very low in plant cells even at induced state. Making things even more difficult, the molecular weight of ACS is similar to that of the large subunit of Rubisco, the most abundant protein in plants. These make it very difficult to visualize the ACS protein from green plant tissues by immunoblot analysis. In this paper, we described the immune-complex ACS assay, which is an ACS activity assay coupled to the immunoprecipitation with a member-specific ACS antibody. By taking advantage of the specificity of a member-specific antibody and the high specific activity of ACS enzyme, this method allows the detection of a specific ACS member in plant cells. In Arabidopsis, ACS is encoded by a small gene family with at least nine different members.
Q： Could you summarize the significance of your paper in layman's terms?
A：Ethylene, a gaseous plant hormone, plays vital roles in plant growth, development, and response to stress. Recent genetic studies revealed a number of important signaling components in the pathways downstream of ethylene. As Dr. Hans Kende pointed out, "Ethylene-regulated processes are mostly initiated by an increase in ethylene synthesis. Ethylene synthesis is under the control of environmental and/or endogenous signals. Thus, to understand ethylene responses, it will be necessary to identify the exogenous and endogenous factors that control ethylene synthesis and to elucidate the signal transduction pathways that lead to an induction of ethylene biosynthesis (Kende, H. 2001. Plant Physiol. 125: 81-84)." This paper revealed one such pathway.
Q： How did you become involved in this research?
A：The major discovery in this paper is a result of good detective work. We first noticed that selected lines of the gain-of-function NtMEK2 transgenic tobacco plants showed ethylene-induced morphology. By following this phenotype, we determined how MAPK activation induced ethylene biosynthesis. In collaboration with Dr. Robert Sharp's lab (Division of Plant Sciences, University of Missouri-Columbia), we first demonstrated that the ethylene production is greatly enhanced after the activation of SIPK/WIPK, the two downstream MAPKs of NtMEK2. By following the biosynthetic enzymes in the ethylene biosynthetic pathway, we found that a subset of ACS isoforms can be directly phosphorylated by MPK6. The phosphorylation stabilizes the ACS protein and leads to ethylene induction.
Shuqun Zhang
Associate Professor
Department of Biochemistry
University of Missouri-Columbia
Columbia, MO, USA
领域：动植物科学
文章标题：一种应激激活的丝裂原活化的蛋白激酶——MPK6对1-氨基环丙烷-1-羧酸合酶的活化诱导了拟南芥乙烯的生物合成。
作者： Liu, YD;Zhang, SQ
杂志：植物细胞
卷：16（12）
问：为什么你认为自己的论文的引用率很高？
答：丝裂原活化的蛋白激酶（MAPK）级联反应是真核细胞受到外源性和内源性刺激时产生的一种极其重要的反应。自从第一个植物MAPK被成功分离和鉴定以来已经有十几年了(Duerr, B.; Gawienowski, M.; Ropp, T.; and Jacobs, T. 1993. Plant Cell 5: 87-96; Jonak, C.; P? A.; B?, L.; Hirt, H.; and Heberle-Bors, E. 1993. Plant J. 3: 611-617)。全基因组测序后发现拟南芥包含20种MAPKs亚型、10种MAPKKs亚型和60多种MAPKKKs亚型 (MAPK Group. 2002. Trends Plant Sci. 7, 301-308)。通过功能获得和功能缺失分析发现植物MAPKs和植物生长、发育和应激反应密切相关。但是这种相关性背后的机制却由于缺乏植物MAPK底物的信息而至今不明。在这篇论文中，我们描述了第一个植物MAPK的底物，1-氨基环丙烷-1-羧酸（ACS）——乙烯生物合成的限速酶。以前我们发现，与熟知的植物应激激素一样，应激引起的MAPK级联反能够应调节乙烯的生物合成(Kim, C.Y.; Liu, Y.; Thorne, E.T.; Yang, H., Fukushig, H.; Gassmann, W.; Hildebrand, D.; Sharp, R.E.; and Zhang, S. 2003. Plant Cell 15: 2707-2718)。这篇论文中，我们证实了与烟草SIPK直系同源的拟南芥MPK6磷酸化ACS2和ACS6后，使ACS蛋白稳定性增强，最终导致细胞内ACS的活性水平升高而产生更多的乙烯。该论文通过对第一个植物MAPK底物的鉴定揭示了MPK6调节植物应激反应的机制。同样重要的是，该研究发现了一个调节乙烯生物合成的信号通路，以及一个重要的植物激素。
问：这篇论文是否描述了一种可以推广的新发现或者新方法？
答：ACS是一种特异性和活性都非常高的酶，在植物细胞内甚至在在被诱导的状态下其表达水平也非常低。更为不利的是ACS的分子量和植物中含量最高的蛋白——Rubisco的大亚基相当。这些因素导致了在免疫印迹实验中很难在绿色植物组织中看到ACS蛋白。这篇论文中，我们应用了免疫复合物ACS测定法，这是一种ACS活性检测和以膜特异性的ACS抗体的免疫沉淀相结合的检测方法。该方法结合了膜ACS抗体的特异性和ACS的高酶活性，能够检测到植物细胞特异性的ACS家族蛋白。在拟南芥内，ACS由一个小的至少有9个不同的基因成员组成的一个基因家族所编码。
问：你能不能用通俗的语言总结一下您这篇论文的意义？
答：作为一种植物的气体激素，乙烯在植物生长，发育以及应激反应中起重要作用。最近，遗传学的研究者们发现了乙烯信号通路下游大量重要的信号元件。正如Hans Kende 博士所指出的那样，乙烯合成的增加极有可能是乙烯调节过程的启动因素。因为乙烯的合成是受环境信号和/或内源性信号所调控的，所以有必要对这些调控乙烯合成的外源性和内源性因子以及诱导乙烯生物合成的信号通路进行鉴定(Kende, H. 2001. Plant Physiol. 125: 81-84)。我们的这篇论文就发现了能诱导乙烯生物合成的信号通路之一。
问：您是怎样开始介入这项研究的？
答：这篇论文主要的发现源于探索性的工作。首先我们注意到被选择的获得功能的NtMEK2转基因烟草品系具有乙烯诱导的形态特征。然后我们就针对这种表型进行研究，最终发现了MAPK的活化是如何诱导乙烯的生物合成的。与Robert Sharp's 博士（哥伦比亚密苏里大学，植物科学部）合作，我们第一次证明了NtMEK2下游的两个MAPKs——SIPK/WIPK的活化极大的增强了乙烯的合成。对乙烯合成通路中生物合成酶的深入研究表明MPK6能够直接磷酸化ACS的不同亚型。磷酸化的ACS蛋白的稳定性增强最终诱导了乙烯合成！
编辑：西门吹血
作者: Shuqun Zhang
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