University of Hohenheim, Institute of Botany 210, 70593 Stuttgart, Germany;
Persoonia. 2009 Jun;22:123-8. doi: 10.3767/003158509X457931. Epub 2009 May 26.
The obligate biotrophic lineages of the white blister rusts (Albuginales, Oomycota) are of ancient origin compared to the rather recently evolved downy mildews, and sophisticated mechanisms of biotrophy and a high degree of adaptation diversity are to be expected in these organisms. Speciation in the biotrophic Oomycetes is usually thought to be the consequence of host adaptation or geographic isolation. Here we report the presence of two distinct species of Albugo on the model plant Arabidopsis thaliana, Albugo candida and Albugo laibachii, the latter being formally described in this manuscript. Both species may occupy the same host within the same environment, but are nevertheless phylogenetically distinct, as inferred from analyses of both mitochondrial and nuclear DNA sequences. Different ways of adapting to their host physiology might constitute an important factor of their different niches. Evidence for this can be gained from the completely different host range of the two pathogens. While Albugo candida is a generalist species, consisting of several physiological varieties, which is able to parasitize a great variety of Brassicaceae, Albugo laibachii has not been found on any host other than Arabidopsis thaliana. Therefore, Albugo laibachii belongs to a group of highly specialised species, like the other known specialist species in Albugo s.s., Albugo koreana, Albugo lepidii and Albugo voglmayrii. The comparative investigation of the effector genes and host targets in the generalist and the specialist species may constitute a model system for elucidating the fundamental processes involved in plant pathogen co-adaptation and speciation.
与相对较新进化而来的霜霉目真菌相比，专性生物营养型的白皮锈菌（Albuginales，卵菌门）的分支具有更古老的起源，因此人们预计这些生物具有复杂的生物营养机制和高度多样化的适应能力。生物营养型卵菌的物种形成通常被认为是宿主适应或地理隔离的结果。在这里，我们报告了在模式植物拟南芥上存在两种不同的白锈属物种，即白头菜白锈菌和莱巴赫白锈菌，后者在本手稿中被正式描述。这两个物种可能在同一环境中占据同一宿主，但从线粒体和核 DNA 序列的分析来看，它们在系统发育上是不同的。适应宿主生理的不同方式可能是它们不同生态位的一个重要因素。这两个病原体完全不同的宿主范围可以证明这一点。白头菜白锈菌是一种专性物种，由几种生理变种组成，能够寄生在各种十字花科植物上，而莱巴赫白锈菌除了拟南芥外，尚未在任何其他宿主上发现。因此，莱巴赫白锈菌属于高度特化物种的一组，就像其他已知的白锈属专性物种白头菜白锈菌、朝鲜白锈菌、菜白蝶白锈菌和燕麦叶白锈菌一样。在专性物种和专性物种中比较研究效应基因和宿主靶标，可能构成阐明植物病原菌协同适应和物种形成所涉及的基本过程的模型系统。
