Levasseur Anthony, Gouret Philippe, Lesage-Meessen Laurence, Asther Michèle, Asther Marcel, Record Eric, Pontarotti Pierre
Phylogenomics Laboratory, EA 3781 Evolution Biologique Université de Provence, Case 19, Pl, V, Hugo, 13331 Marseille Cedex 03, France.
BMC Evol Biol. 2006 Nov 8;6:92. doi: 10.1186/1471-2148-6-92.
There have been many claims of adaptive molecular evolution, but what role does positive selection play in functional divergence? The aim of this study was to test the relationship between evolutionary and functional shifts with special emphasis on the role of the environment. For this purpose, we studied the fungal lipase/feruloyl esterase A family, whose functional diversification makes it a very promising candidate.
The results suggested functional shift following a duplication event where neofunctionalisation of feruloyl esterase A had occurred with conservation of the ancestral lipase function. Evolutionary shift was detected using the branch-site model for testing positive selection on individual codons along specific lineages. Positively selected amino acids were detected. Furthermore, biological data obtained from site-directed mutagenesis experiments clearly demonstrated that certain amino acids under positive selection were involved in the functional shift. We reassessed evolutionary history in terms of environmental response, and hypothesized that environmental changes such as colonisation by terrestrial plants might have driven adaptation by functional diversification in Euascomycetes (Aspergilli), thus conferring a selective advantage on this group.
The results reported here illustrate a rare example of connection between fundamental events in molecular evolution. We demonstrated an unequivocal connection between evolutionary and functional shifts, which led us to conclude that these events were probably linked to environmental change.
已有许多关于适应性分子进化的说法，但正选择在功能分化中起什么作用呢？本研究的目的是检验进化转变与功能转变之间的关系，特别强调环境的作用。为此，我们研究了真菌脂肪酶/阿魏酸酯酶A家族，其功能多样化使其成为一个非常有前景的候选对象。
结果表明，在一次复制事件后发生了功能转变，其中阿魏酸酯酶A发生了新功能化，而祖先脂肪酶功能得以保留。使用分支位点模型检测沿着特定谱系的单个密码子上的正选择，从而检测到进化转变。检测到了正选择的氨基酸。此外，从定点诱变实验获得的生物学数据清楚地表明，某些处于正选择下的氨基酸参与了功能转变。我们根据环境响应重新评估了进化历史，并假设诸如陆地植物定殖等环境变化可能通过真子囊菌（曲霉属）的功能多样化驱动了适应性，从而赋予该类群选择性优势。
此处报道的结果说明了分子进化中基本事件之间联系的一个罕见例子。我们证明了进化转变与功能转变之间明确的联系，这使我们得出结论，这些事件可能与环境变化有关。
