Genome Biol Evol. 2012;4(3):289-93. doi: 10.1093/gbe/evs011. Epub 2012 Jan 31.
A cluster composed of four structural and two regulatory genes found in several species of the fungal genus Fusarium (class Sordariomycetes) is responsible for the production of the red pigment bikaverin. We discovered that the unrelated fungus Botrytis cinerea (class Leotiomycetes) contains a cluster of five genes that is highly similar in sequence and gene order to the Fusarium bikaverin cluster. Synteny conservation, nucleotide composition, and phylogenetic analyses of the cluster genes indicate that the B. cinerea cluster was acquired via horizontal transfer from a Fusarium donor. Upon or subsequent to the transfer, the B. cinerea gene cluster became inactivated; one of the four structural genes is missing, two others are pseudogenes, and the fourth structural gene shows an accelerated rate of nonsynonymous substitutions along the B. cinerea lineage, consistent with relaxation of selective constraints. Interestingly, the bik4 regulatory gene is still intact and presumably functional, whereas bik5, which is a pathway-specific regulator, also shows a mild but significant acceleration of evolutionary rate along the B. cinerea lineage. This selective preservation of the bik4 regulator suggests that its conservation is due to its likely involvement in other non-bikaverin-related biological processes in B. cinerea. Thus, in addition to novel metabolism, horizontal transfer of wholesale metabolic gene clusters might also be contributing novel regulation.
由四个结构基因和两个调节基因组成的簇存在于几种镰刀菌属真菌（Sordariomycetes 纲）中，负责产生红色素血根碱。我们发现，不相关的真菌 Botrytis cinerea（Leotiomycetes 纲）含有一个由五个基因组成的簇，其序列和基因顺序与 Fusarium bikaverin 簇高度相似。簇基因的同线性保守性、核苷酸组成和系统发育分析表明，B. cinerea 簇是通过水平转移从 Fusarium 供体获得的。在转移之后或之后，B. cinerea 基因簇失活；四个结构基因之一缺失，另外两个是假基因，第四个结构基因在 B. cinerea 谱系中表现出加速的非同义替换率，与选择压力的放松一致。有趣的是，bik4 调节基因仍然完整且可能具有功能，而 bik5 是一种途径特异性调节剂，也沿着 B. cinerea 谱系表现出轻微但显著的进化速率加速。bik4 调节基因的这种选择性保存表明，其保守性可能与其在 B. cinerea 中参与其他非血根碱相关生物过程有关。因此，除了新的代谢途径外，代谢基因簇的水平转移也可能导致新的调控。
