Zimmermann Dirk, Gomez-Barrera Juan A, Pasule Christian, Brack-Frick Ursula B, Sieferer Elke, Nicholson Tim M, Pfannstiel Jens, Stintzi Annick, Schaller Andreas
Institute of Plant Physiology and Biotechnology (D.Z., J.A.G.-B., C.P., E.S., T.M.N., A.St., A.Sc.) and Service Unit Mass Spectrometry (J.P.), University of Hohenheim, 70593 Stuttgart, Germany; andEidgenössisch Technische Hochschule Zürich, Institute of Plant Sciences, 8092 Zurich, Switzerland (U.B.B.-F.).
Institute of Plant Physiology and Biotechnology (D.Z., J.A.G.-B., C.P., E.S., T.M.N., A.St., A.Sc.) and Service Unit Mass Spectrometry (J.P.), University of Hohenheim, 70593 Stuttgart, Germany; andEidgenössisch Technische Hochschule Zürich, Institute of Plant Sciences, 8092 Zurich, Switzerland (U.B.B.-F.)
Plant Physiol. 2016 Jun;171(2):1456-69. doi: 10.1104/pp.16.00513. Epub 2016 May 2.
In contrast to mammalian matrix metalloproteinases (MMPs) that play important roles in the remodeling of the extracellular matrix in animals, the proteases responsible for dynamic modifications of the plant cell wall are largely unknown. A possible involvement of MMPs was addressed by cloning and functional characterization of Sl2-MMP and Sl3-MMP from tomato (Solanum lycopersicum). The two tomato MMPs were found to resemble mammalian homologs with respect to gelatinolytic activity, substrate preference for hydrophobic amino acids on both sides of the scissile bond, and catalytic properties. In transgenic tomato seedlings silenced for Sl2/3-MMP expression, necrotic lesions were observed at the base of the hypocotyl. Cell death initiated in the epidermis and proceeded to include outer cortical cell layers. In later developmental stages, necrosis spread, covering the entire stem and extending into the leaves of MMP-silenced plants. The subtilisin-like protease P69B was identified as a substrate of Sl2- and Sl3-MMP. P69B was shown to colocalize with Sl-MMPs in the apoplast of the tomato hypocotyl, it exhibited increased stability in transgenic plants silenced for Sl-MMP activity, and it was cleaved and inactivated by Sl-MMPs in vitro. The induction of cell death in Sl2/3-MMP-silenced plants depended on P69B, indicating that Sl2- and Sl3-MMP act upstream of P69B in an extracellular proteolytic cascade that contributes to the regulation of cell death in tomato.
与在动物细胞外基质重塑中起重要作用的哺乳动物基质金属蛋白酶（MMP）不同，负责植物细胞壁动态修饰的蛋白酶在很大程度上尚不清楚。通过从番茄（Solanum lycopersicum）中克隆Sl2-MMP和Sl3-MMP并对其进行功能表征，探讨了MMPs可能的参与情况。发现这两种番茄MMP在明胶酶活性、对切割键两侧疏水氨基酸的底物偏好以及催化特性方面与哺乳动物同源物相似。在Sl2/3-MMP表达沉默的转基因番茄幼苗中，在下胚轴基部观察到坏死病变。细胞死亡始于表皮，并扩展到包括外层皮层细胞层。在后期发育阶段，坏死扩散，覆盖整个茎部并延伸到MMP沉默植物的叶片中。枯草杆菌蛋白酶样蛋白酶P69B被鉴定为Sl2-和Sl3-MMP的底物。P69B显示与Sl-MMPs在番茄下胚轴的质外体中共定位，在Sl-MMP活性沉默的转基因植物中其稳定性增加，并且在体外被Sl-MMPs切割并失活。Sl2/3-MMP沉默植物中细胞死亡的诱导依赖于P69B，这表明Sl2-和Sl3-MMP在细胞外蛋白水解级联反应中作用于P69B的上游，该级联反应有助于调节番茄中的细胞死亡。
