Lost in the middle of nowhere:: the AvrLm1 avirulence gene of the Dothideomycete Leptosphaeria maculans
Lost in the middle of nowhere:: the AvrLm1 avirulence gene of the Dothideomycete Leptosphaeria maculans
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DOI：
10.1111/j.1365-2958.2006.05076.x
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发表时间：
2006-04-01
影响因子：
3.6
通讯作者：
Rouxel, T
中科院分区：
文献类型：
--
作者：
Gout, L;Fudal, I;Rouxel, T
maculans是一种引起油菜茎溃疡病的多孢子菌，它与宿主植物发生基因对基因的相互作用。迄今为止，在芸苔属植物中已鉴定出9个抗性基因（Rlm1-9），而在L. maculans中，相应的9个毒力基因（AvrLm1-9）已定位在4个独立的位点上，从而揭示了3个和4个连锁毒力基因的两个集群。在这里，我们报告了AvrLm1基于地图克隆的完成。AvrLm1在7.3厘米的间隔内被遗传圈定，对应于439 kb的BAC序列。AvrLm1是一个分离于269 kb非编码异染色质样区域的单拷贝基因。该区域由四个长末端重复（LTR）反转录转座子的许多退化的嵌套拷贝组成，包括phly和三个新的吉普赛样反转录转座子。AvrLm1在强毒株的功能互补后恢复了Rlm1品种的无毒表型。AvrLm1同源物未在其他钩端绦虫物种或已知的真菌基因组中检测到，包括密切相关的Stagonospora nodorum。预测的AvrLm1蛋白由205个氨基酸组成，其中只有一个是半胱氨酸残基。它含有提示细胞外定位的肽信号。与大多数其他真菌无毒基因不同，AvrLm1是组成性表达的，在植物感染后表达水平可能会增加，这表明AvrLm1的表达缺乏严格的调控。
Leptosphaeria maculans, a Dothideomycete causing stem canker on oilseed rape (Brassica napus), develops gene-for-gene interactions with its host plants. To date, nine resistance genes (Rlm1-9) have been identified in Brassica spp. The corresponding nine avirulence genes (AvrLm1-9) in L. maculans have been mapped at four independent loci, thereby revealing two clusters of three and four linked avirulence genes. Here, we report the completion of map-based cloning of AvrLm1. AvrLm1 was genetically delineated within a 7.3 centimorgan interval corresponding to a 439 kb BAC contig. AvrLm1 is a single copy gene isolated within a 269 kb non-coding, heterochromatin-like region. The region comprised a number of degenerated, nested copies of four long-terminal repeat (LTR) retrotransposons, including Pholy and three novel Gypsy-like retrotransposons. AvrLm1 restored the avirulent phenotype on Rlm1 cultivars following functional complementation of virulent isolates. AvrLm1 homologues were not detected in other Leptosphaeria species or in known fungal genomes including the closely related species Stagonospora nodorum. The predicted AvrLm1 protein is composed of 205 amino acids, of which only one is a cysteine residue. It contains a peptide signal suggesting extracellular localization. Unlike most other fungal avirulence genes, AvrLm1 is constitutively expressed, with a probable increased level of expression upon plant infection, suggesting the absence of tight regulation of AvrLm1 expression.