Department of Ecophysiology, Max Planck Institute for Terrestrial Microbiology, Marburg, Germany.
Mol Biol Evol. 2011 Feb;28(2):1083-97. doi: 10.1093/molbev/msq292. Epub 2010 Oct 29.
Genetic programs underlying multicellular morphogenesis and cellular differentiation are most often associated with eukaryotic organisms, but examples also exist in bacteria such as the formation of multicellular, spore-filled fruiting bodies in the order Myxococcales. Most members of the Myxococcales undergo a multicellular developmental program culminating in the formation of spore-filled fruiting bodies in response to starvation. To gain insight into the evolutionary history of fruiting body formation in Myxococcales, we performed a comparative analysis of the genomes and transcriptomes of five Myxococcales species, four of these undergo fruiting body formation (Myxococcus xanthus, Stigmatella aurantiaca, Sorangium cellulosum, and Haliangium ochraceum) and one does not (Anaeromyxobacter dehalogenans). Our analyses show that a set of 95 known M. xanthus development-specific genes--although suffering from a sampling bias--are overrepresented and occur more frequently than an average M. xanthus gene in S. aurantiaca, whereas they occur at the same frequency as an average M. xanthus gene in S. cellulosum and in H. ochraceum and are underrepresented in A. dehalogenans. Moreover, genes for entire signal transduction pathways important for fruiting body formation in M. xanthus are conserved in S. aurantiaca, whereas only a minority of these genes are conserved in A. dehalogenans, S. cellulosum, and H. ochraceum. Likewise, global gene expression profiling of developmentally regulated genes showed that genes that upregulated during development in M. xanthus are overrepresented in S. aurantiaca and slightly underrepresented in A. dehalogenans, S. cellulosum, and H. ochraceum. These comparative analyses strongly indicate that the genetic programs for fruiting body formation in M. xanthus and S. aurantiaca are highly similar and significantly different from the genetic program directing fruiting body formation in S. cellulosum and H. ochraceum. Thus, our analyses reveal an unexpected level of plasticity in the genetic programs for fruiting body formation in the Myxococcales and strongly suggest that the genetic program underlying fruiting body formation in different Myxococcales is not conserved. The evolutionary implications of this finding are discussed.
多细胞形态发生和细胞分化的遗传程序通常与真核生物有关，但在细菌中也存在一些例子，例如粘球菌目中形成多细胞、充满孢子的子实体。大多数粘球菌目成员经历多细胞发育程序，最终在饥饿时形成充满孢子的子实体。为了深入了解粘球菌目中子实体形成的进化历史，我们对五个粘球菌目物种的基因组和转录组进行了比较分析，其中四个物种经历了子实体形成（黄色粘球菌、橙色粘球菌、纤维堆囊菌和橙色黄杆菌），一个物种没有（脱硫弧菌）。我们的分析表明，一组 95 个已知的黄色粘球菌发育特异性基因——尽管存在采样偏差——过度表达，并且在橙色粘球菌中比黄色粘球菌的平均基因更频繁出现，而在纤维堆囊菌和橙色黄杆菌中与黄色粘球菌的平均基因出现频率相同，并且在脱硫弧菌中表达不足。此外，对于黄色粘球菌中形成子实体至关重要的整个信号转导途径的基因在橙色粘球菌中被保守，而在脱硫弧菌、纤维堆囊菌和橙色黄杆菌中只有少数这些基因被保守。同样，发育调节基因的全局基因表达谱分析表明，在黄色粘球菌中发育过程中上调的基因在橙色粘球菌中过度表达，在脱硫弧菌、纤维堆囊菌和橙色黄杆菌中略有表达不足。这些比较分析强烈表明，黄色粘球菌和橙色粘球菌形成子实体的遗传程序非常相似，而指导纤维堆囊菌和橙色黄杆菌形成子实体的遗传程序则有很大不同。因此，我们的分析揭示了粘球菌目中子实体形成遗传程序的惊人可塑性，并强烈表明不同粘球菌目中子实体形成的遗传程序没有保守。讨论了这一发现的进化意义。
