英国、德国、瑞士三国科学家近日通过研究，揭示了病菌如何征服植物的防御系统。研究人员表示，理解病菌入侵植物的机制将能帮助科学家研发出新的对抗植物疾病的方法，而无需使用对人体和环境有害的杀虫剂。相关论文12月4日在线发表于《当代生物学》（Current Biology）。
英国伦敦帝国理工学院生命科学系的John Mansfield和德国、瑞士的合作者一起，以模式植物拟南芥为实验对象，检查了其感染细菌性斑点病后分子水平上的变化。研究人员发现，病菌向拟南芥细胞注入了一种蛋白，灭活并破坏了细胞表面的受体，而这些受体的作用是在病菌入侵时向植物发出警报。这就像是盗贼入室盗窃前摘除防盗警报一样。
通常情况下，细胞表面受体会发动连锁反应，产生抗菌化合物，杀灭入侵病菌。而受体的失活则从起始阶段停止了植物的防御机制。
Mansfield表示：“受体一旦被破坏，植物的防御就会不起作用，病菌从而能够快速传播，吞食植物，遇不到丝毫的抵抗。”
他说：“除了黑斑病之外，这一领域的研究还具有更加广泛的意义，因为所有致植物生病的细菌可能采取了相同的攻击策略，来抑制植物的抵抗。我们对于致病菌如何征服农作物的先天免疫了解得越多，就越有可能开发出新的疾病控制方法，而无需使用具潜在危害的杀虫剂。”（生物谷Bioon.com）
生物谷推荐原始出处：
Current Biology，doi:10.1016/j.cub.2008.10.063，John W. Mansfield，Silke Robatzek
Plant Pattern-Recognition Receptor FLS2 Is Directed for Degradation by the Bacterial Ubiquitin Ligase AvrPtoB
Vera G?hre1,Thomas Spallek1,Heidrun H?weker1,Sophia Mersmann1,Tobias Mentzel2,Thomas Boller2,Marta de Torres3,4,John W. Mansfield3andSilke Robatzek1,,
1 Max-Planck-Institute for Plant Breeding Research, Carl-von-Linne-Weg 10, 50829 Cologne, Germany
2 Zurich-Basel Plant Science Center, University Basel, Hebelstrasse 1, 4056 Basel, Switzerland
3 Imperial College London, Division of Biology, South Kensington Campus, London SW7 2AZ, UK
SUMMARY
An important layer of active defense in plant immunity is the detection of pathogen-associated molecular patterns (PAMPs) mediated by cell-surface receptors. For the establishment of disease, pathogens depend on the ability to overcome PAMP perception and disable plant signaling pathways activated in response to PAMPs. Pattern recognition receptors (PRRs) are therefore prime targets for pathogen effectors. FLS2, its coreceptor BAK1, and EFR encode receptor-like kinases that play a role in immunity against bacterial pathogens.Here, we report that virulence of Pseudomonas syringae pv tomato DC3000 (PtoDC3000) in Arabidopsis is enhanced through the action of its effector AvrPtoB, which promotes degradation of FLS2. We show that AvrPtoB, through its N terminus, associates with FLS2 and BAK1, of which interaction with FLS2 is enhanced by flg22 activation. In vitro, AvrPtoB is active as an E3 ligase to catalyze polyubiquitination of the kinase domain of FLS2, a process confirmed in planta. Full enhancement of PtoDC3000 virulence appears to require the E3 ligase activity of AvrPtoB.AvrPtoB, initially identified through its activation of hypersensitive resistance in tomato cultivars expressing the Pto kinase, is composed of at least two functional domains: the N terminus is responsible for interaction with Pto, and the C terminus carries an E3 ligase activity. Based on our findings, we propose that both domains of AvrPtoB act together to support the virulence of PtoDC3000 in Arabidopsis through their ability to eliminate FLS2 from the cell periphery, and probably also other PAMP sensors that are constitutively expressed or induced after pathogen challenge.
