Institute of Fruit Tree and Tea Science, National Agriculture and Food Research Organization (NARO), Fujimoto 2-1, Tsukuba, Ibaraki, 305-8605, Japan.
Genetic Resources Center, NARO, Kannondai 2-1-2, Tsukuba, Ibaraki, 305-8602, Japan.
Sci Rep. 2019 Mar 7;9(1):3836. doi: 10.1038/s41598-019-40754-9.
The kiwifruit bacterial canker pathogen, Pseudomonas syringae pv. actinidiae (Psa), causes enormous economic damages in many kiwifruit producing countries. In 2015, biovar 6, the novel biovar of Psa, was found in Nagano Prefecture, Japan. The genomes of two representative strains of biovar 6 (MAFF 212134 and MAFF 212141) were sequenced and analysed, indicating that their genomes are the most similar to that of biovar 3 among the known Psa biovars, based on average nucleotide identity analysis. Biovar 3 has neither the phaseolotoxin synthesis gene cluster nor the coronatine synthesis gene cluster, whereas biovar 6 has both clusters and produces both phytotoxins. We found that biovar 6 possesses 29 type III secreted effector (T3SE) genes, among which avrRps4 and hopBI1 are unique to biovar 6. The expression of T3SE genes and two phytotoxin synthesis gene clusters of biovar 6 during the early stages of host infection was investigated using RNA-Seq analysis, showing that these genes could be grouped into three categories: constantly expressed genes, constantly suppressed genes, and temporarily induced genes. A PCR assay was established to differentiate biovar 6 strains from the other Psa biovars and the closely related pathovar, pv. actinidifoliorum, by using avrRps4 as a biovar 6-specific marker gene.
猕猴桃溃疡病菌（Pseudomonas syringae pv. actinidiae，Psa）是一种引起猕猴桃产业重大经济损失的病原菌。2015 年，在日本长野县发现了该病菌的一个新的生物变种 6 型（biovar 6）。本研究对两个 6 型代表菌株（MAFF 212134 和 MAFF 212141）的基因组进行了测序和分析，结果表明，基于平均核苷酸同一性分析，其基因组与已知的 Psa 生物变种 3 最为相似。生物变种 3 既没有类毒素合成基因簇，也没有冠菌素合成基因簇，而 6 型则同时拥有这两个基因簇，并能产生这两种植物毒素。我们发现 6 型拥有 29 个 III 型分泌效应子（T3SE）基因，其中 avrRps4 和 hopBI1 是 6 型所特有的。通过 RNA-Seq 分析研究了 6 型在宿主感染早期 T3SE 基因和两个植物毒素合成基因簇的表达情况，结果表明这些基因可分为三类：持续表达基因、持续抑制基因和暂时诱导基因。建立了一种 PCR 检测方法，可利用 avrRps4 作为 6 型特有的标记基因，将 6 型菌株与其他 Psa 生物变种和密切相关的 pv. actinidifoliorum 区分开来。
