Abstract
Nematodes are very common animals and they have repeatedly evolved parasitic lifestyles during their evolutionary history. Recently, the genomes of many nematodes, especially parasitic species, have been determined, potentially giving an insight into the genetic and genomic basis of nematodes’ parasitism. But, to achieve this, phylogenetically appropriate comparisons of genomes of free-living and parasitic species are needed. Achieving this has often been hampered by the relative lack of information about key free-living species. While such comparative approaches will eventually succeed, I suggest that a synthetic biology approach – moving free-living nematodes towards a parasitic lifestyle – will be our ultimate test of truly understanding the genetic and genomic basis of nematode parasitism.
Highlights
Nematodes are very common animals and they have repeatedly evolved parasitic lifestyles during their evolutionary history
The phenotypic analogy of free-living nematode arrested larvae and parasitic nematode infective larvae is probably not underpinned by an analogous molecular control. This does not necessarily mean that the phenotypic analogy is wrong, but that genetic control of phenotypes can evolve without apparently changing the phenotype [19]. This again argues for phylogenetically appropriate comparisons between freeliving and parasitic taxa when trying to understand the evolution of parasitism
Other gene families that became comparatively enlarged as parasitism evolved include those coding for acetylcholinesterases and prolyl endopeptidases [25]. Some of these gene families have been suggested to be associated with the parasitic lifestyle of other parasitic nematodes – various protease-coding genes [7] as well as SCP/TAPS protein coding genes suggesting that these proteins may play a fundamental role in nematode parasitism more generally [26]
Summary
Nematodes are very common animals and they have repeatedly evolved parasitic lifestyles during their evolutionary history. Because parasitism has evolved multiple times, informative genomic comparisons between free-living and parasitic species are only possible when the species being compared are from within the same nematode clade or subclade This is because such comparisons involve the point at which the relevant evolutionary transition from a free-living to a parasitic lifestyle occurred. This does not necessarily mean that the phenotypic analogy is wrong, but that genetic control of phenotypes can evolve without apparently changing the phenotype [19] This again argues for phylogenetically appropriate comparisons between freeliving and parasitic taxa when trying to understand the evolution of parasitism
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