Oh Chang-Sik, Beer Steven V
Department of Plant Pathology, Cornell University, 334 Plant Science Building, Ithaca, NY 14853, USA.
FEMS Microbiol Lett. 2005 Dec 15;253(2):185-92. doi: 10.1016/j.femsle.2005.09.051. Epub 2005 Oct 13.
The bacterial plant pathogen, Erwinia amylovora, causes the devastating disease known as fire blight in some Rosaceous plants like apple, pear, quince, raspberry and several ornamentals. Knowledge of the factors affecting the development of fire blight has mushroomed in the last quarter century. On the molecular level, genes encoding a Hrp type III secretion system, genes encoding enzymes involved in synthesis of extracellular polysaccharides and genes facilitating the growth of E. amylovora in its host plants have been characterized. The Hrp pathogenicity island, delimited by genes suggesting horizontal gene transfer, is composed of four distinct regions, the hrp/hrc region, the HEE (Hrp effectors and elicitors) region, the HAE (Hrp-associated enzymes) region, and the IT (Island transfer) region. The Hrp pathogenicity island encodes a Hrp type III secretion system (TTSS), which delivers several proteins from bacteria to plant apoplasts or cytoplasm. E. amylovora produces two exopolysaccharides, amylovoran and levan, which cause the characteristic fire blight wilting symptom in host plants. In addition, other genes, and their encoded proteins, have been characterized as virulence factors of E. amylovora that encode enzymes facilitating sorbitol metabolism, proteolytic activity and iron harvesting. This review summarizes our understanding of the genes and gene products of E. amylovora that are involved in the development of the fire blight disease.
细菌性植物病原菌——梨火疫欧文氏菌，可在苹果、梨、榅桲、覆盆子等一些蔷薇科植物以及几种观赏植物中引发一种名为火疫病的毁灭性病害。在过去的四分之一世纪里，人们对影响火疫病发生发展的因素的了解迅速增加。在分子水平上，编码Hrp III型分泌系统的基因、编码参与胞外多糖合成的酶的基因以及促进梨火疫欧文氏菌在其寄主植物中生长的基因已得到鉴定。由暗示水平基因转移的基因界定的Hrp致病岛由四个不同区域组成，即hrp/hrc区域、HEE（Hrp效应子和激发子）区域、HAE（Hrp相关酶）区域和IT（岛转移）区域。Hrp致病岛编码一个Hrp III型分泌系统（TTSS），该系统将多种蛋白质从细菌传递到植物质外体或细胞质中。梨火疫欧文氏菌产生两种胞外多糖，即淀粉果聚糖和果聚糖，它们在寄主植物中引发火疫病特有的萎蔫症状。此外，其他一些基因及其编码的蛋白质已被鉴定为梨火疫欧文氏菌的毒力因子，这些基因编码促进山梨醇代谢、蛋白水解活性和铁摄取的酶。本综述总结了我们对参与火疫病发生发展的梨火疫欧文氏菌基因和基因产物的理解。
