Den Herder Griet, De Keyser Annick, De Rycke Riet, Rombauts Stephane, Van de Velde Willem, Clemente María R, Verplancke Christa, Mergaert Peter, Kondorosi Eva, Holsters Marcelle, Goormachtig Sofie
Department of Plant Systems Biology, Flanders Institute for Biotechnology and Department of Molecular Genetics, Ghent University, B-9052 Gent, Belgium.
Plant Physiol. 2008 Sep;148(1):369-82. doi: 10.1104/pp.108.119453. Epub 2008 Jul 3.
Protein ubiquitination is a posttranslational regulatory process essential for plant growth and interaction with the environment. E3 ligases, to which the seven in absentia (SINA) proteins belong, determine the specificity by selecting the target proteins for ubiquitination. SINA proteins are found in animals as well as in plants, and a small gene family with highly related members has been identified in the genome of rice (Oryza sativa), Arabidopsis (Arabidopsis thaliana), Medicago truncatula, and poplar (Populus trichocarpa). To acquire insight into the function of SINA proteins in nodulation, a dominant negative form of the Arabidopsis SINAT5 was ectopically expressed in the model legume M. truncatula. After rhizobial inoculation of the 35S:SINAT5DN transgenic plants, fewer nodules were formed than in control plants, and most nodules remained small and white, a sign of impaired symbiosis. Defects in rhizobial infection and symbiosome formation were observed by extensive microscopic analysis. Besides the nodulation phenotype, transgenic plants were affected in shoot growth, leaf size, and lateral root number. This work illustrates a function for SINA E3 ligases in a broad spectrum of plant developmental processes, including nodulation.
蛋白质泛素化是植物生长及与环境互作所必需的一种翻译后调控过程。七缺失（SINA）蛋白所属的E3连接酶通过选择要进行泛素化的靶蛋白来决定特异性。SINA蛋白在动物和植物中均有发现，并且在水稻（Oryza sativa）、拟南芥（Arabidopsis thaliana）、蒺藜苜蓿（Medicago truncatula）和杨树（Populus trichocarpa）的基因组中已鉴定出一个由高度相关成员组成的小基因家族。为深入了解SINA蛋白在结瘤中的功能，拟南芥SINAT5的显性负性形式在模式豆科植物蒺藜苜蓿中异位表达。对35S:SINAT5DN转基因植物进行根瘤菌接种后，形成的根瘤比对照植物少，并且大多数根瘤仍然小且呈白色，这是共生受损的迹象。通过广泛的显微镜分析观察到根瘤菌感染和共生体形成存在缺陷。除了结瘤表型外，转基因植物在地上部生长、叶片大小和侧根数量方面也受到影响。这项工作阐明了SINA E3连接酶在包括结瘤在内的广泛植物发育过程中的功能。
