一种毒性蛋白促进植物传染病

xielirong

美国维吉尼亚理工学院生物信息研究所（VBI）的研究者及其同事的一项最新研究，证实了某家族毒性蛋白在植物病原体Phytophthora sojae的传染过程中起到了重要作用。相关论文发表在《植物细胞》（The Plant Cell）上。

VBI的教授Brett Tyler及其同事、中国南京农业大学以及荷兰Wageningen大学的研究者，共同检测了这种名为Avr1b的蛋白在P. sojae中的功能，结果发现Avr1b可以抑制植物免疫中所谓的“程序性细胞凋亡”这一重要过程。细胞凋亡是细胞一种内在的自毁机理，可以杀掉被感染的植物组织并使毒素充斥其中，从而使病原体不能再吞噬植物组织。

P. sojae是一种霉菌植物病原体，可以严重损害大豆植物。在美国，每年农场主都会因P. sojae受到100万到200万美元的损失，世界范围内则更多。通过改变该效应蛋白的关键性氨基酸残基，研究者发现，Avr1b是通过C端蛋白的两个氨基酸序列（W和Y）来抑制细胞凋亡。Tyler教授的研究组最近在其它卵菌病原体的毒性蛋白中也发现了这些氨基酸序列。

Tyler认为，如同人类HIV病毒一样，卵菌植物病原体病症是通过攻击植物的免疫系统来达到感染它们的目的。


（The Plant Cell），10.1105/tpc.107.057067，Daolong Dou, Brett M. Tyler

Conserved C-Terminal Motifs Required for Avirulence and Suppression of Cell Death by Phytophthora sojae effector Avr1b
Daolong Dou 1, Shiv D. Kale 1, Xinle Wang 2, Yubo Chen 2, Qunqing Wang 2, Xia Wang 1, Rays H.Y. Jiang 3, Felipe D. Arredondo 1, Ryan G. Anderson 4, Poulami B. Thakur 4, John M. McDowell 4, Yuanchao Wang 2, and Brett M. Tyler

1 Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
2 Department of Plant Pathology, Nanjing Agricultural University, Nanjing 210095, China
3 Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061; Laboratory of Phytopathology, Wageningen University, NL-6709 PD Wageningen, The Netherlands
4 Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061
5 Virginia Bioinformatics Institute, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061; Department of Plant Pathology, Physiology, and Weed Science, Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061


The sequenced genomes of oomycete plant pathogens contain large superfamilies of effector proteins containing the protein translocation motif RXLR-dEER. However, the contributions of these effectors to pathogenicity remain poorly understood. Here, we show that the Phytophthora sojae effector protein Avr1b can contribute positively to virulence and can suppress programmed cell death (PCD) triggered by the mouse BAX protein in yeast, soybean (Glycine max), and Nicotiana benthamiana cells. We identify three conserved motifs (K, W, and Y) in the C terminus of the Avr1b protein and show that mutations in the conserved residues of the W and Y motifs reduce or abolish the ability of Avr1b to suppress PCD and also abolish the avirulence interaction of Avr1b with the Rps1b resistance gene in soybean. W and Y motifs are present in at least half of the identified oomycete RXLR-dEER effector candidates, and we show that three of these candidates also suppress PCD in soybean. Together, these results indicate that the W and Y motifs are critical for the interaction of Avr1b with host plant target proteins and support the hypothesis that these motifs are critical for the functions of the very large number of predicted oomycete effectors that contain them.