Lee Soo Chan, Weiss Louis M, Heitman Joseph
Department of Molecular Genetics and Microbiology, Duke University Medical Center, Durham, NC 27710, USA.
Commun Integr Biol. 2009 Sep;2(5):414-7. doi: 10.4161/cib.2.5.8846.
Microsporidia are obligate intracellular pathogens mainly infecting both vertebrate and invertebrate hosts. The group comprises approximately 150 genera with 1,200 species. Due to sequence divergence phylogenic reconstructions that are solely based on DNA sequence have been unprecise for these pathogens. Our previous study identified that three microsporidian genomes contained a putative sex-related locus similar to that of zygomycetes. In a comparison of genome architecture of the microsporidia to other fungi, Rhizopus oryzae, a zygomycete fungus, shared more common gene clusters with Encephalitozoon cuniculi, a microsporidian. This provides evidence supporting the hypothesis that microsporidia and zygomycete fungi may share a more recent common ancestor than other fungal lineages. Genetic recombination is an important outcome of sexual development. We describe genetic markers which will enable tests of whether sex occurs within E. cuniculi populations by analyzing tandem repeat DNA regions in three different isolates. Taken together, the phylogenetic relationship of microsporidia to fungi and the presence of a sex-related locus in their genomes suggest the microsporidia may have an extant sexual cycle. In addition, we describe recently reported evidence of horizontal gene transfer from Chlamydia to the E. cuniculi genome and show that these two obligate intracellular pathogens can infect the same host cells.
微孢子虫是专性细胞内病原体，主要感染脊椎动物和无脊椎动物宿主。该类群包括约150个属，1200个物种。由于序列差异，仅基于DNA序列的系统发育重建对于这些病原体来说并不精确。我们之前的研究发现，三种微孢子虫基因组包含一个类似于接合菌的假定性别相关位点。在将微孢子虫的基因组结构与其他真菌进行比较时，接合菌纲真菌米根霉与微孢子虫兔脑炎微孢子虫共享了更多的共同基因簇。这为支持微孢子虫和接合菌纲真菌可能比其他真菌谱系拥有更近的共同祖先这一假说提供了证据。基因重组是有性发育的一个重要结果。我们描述了一些遗传标记，通过分析三种不同分离株中的串联重复DNA区域，这些标记将能够测试兔脑炎微孢子虫种群中是否发生有性生殖。综上所述，微孢子虫与真菌的系统发育关系以及它们基因组中存在性别相关位点表明微孢子虫可能具有现存的有性生殖周期。此外，我们描述了最近报道的从衣原体到兔脑炎微孢子虫基因组的水平基因转移证据，并表明这两种专性细胞内病原体可以感染相同的宿主细胞。
