Department of Plant Pathology and Plant-Microbe Biology, Cornell University, Ithaca, NY 14853, USA.
Phytopathology. 2011 Aug;101(8):935-44. doi: 10.1094/PHYTO-12-10-0339.
Strains of Erwinia amylovora, the bacterium causing the disease fire blight of rosaceous plants, are separated into two groups based on host range: Spiraeoideae and Rubus strains. Spiraeoideae strains have wide host ranges, infecting plants in many rosaceous genera, including apple and pear. In the field, Rubus strains infect the genus Rubus exclusively, which includes raspberry and blackberry. Based on comparisons of limited sequence data from a Rubus and a Spiraeoideae strain, the gene eop1 was identified as unusually divergent, and it was selected as a possible host specificity factor. To test this, eop1 genes from a Rubus strain and a Spiraeoideae strain were cloned and mutated. Expression of the Rubus-strain eop1 reduced the virulence of E. amylovora in immature pear fruit and in apple shoots. Sequencing the orfA-eop1 regions of several strains of E. amylovora confirmed that forms of eop1 are conserved among strains with similar host ranges. This work provides evidence that eop1 from a Rubus-specific strain can function as a determinant of host specificity in E. amylovora.
韧皮部杆菌，引起蔷薇科植物火疫病的细菌，根据其宿主范围可分为两组：蔷薇科组和悬钩子组。蔷薇科组菌株具有广泛的宿主范围，感染包括苹果和梨在内的许多蔷薇科属植物。在野外，悬钩子组菌株只感染悬钩子属，其中包括覆盆子和黑莓。基于对一株悬钩子组菌株和一株蔷薇科组菌株的有限序列数据的比较，鉴定出基因 eop1 异常分化，并将其选为可能的宿主特异性因子。为了验证这一点，从一株悬钩子组菌株和一株蔷薇科组菌株中克隆并突变了 eop1 基因。表达来自悬钩子组菌株的 eop1 基因降低了不成熟的梨果实和苹果嫩枝中韧皮部杆菌的毒力。对几种韧皮部杆菌菌株的 orfA-eop1 区进行测序证实，具有相似宿主范围的菌株中 eop1 形式是保守的。这项工作提供了证据表明，来自悬钩子特异性菌株的 eop1 可以作为韧皮部杆菌宿主特异性决定因素发挥作用。
