@article{PAR00003095,
  title = {{V}iral cystatin evolution and three-dimensional structure modelling : a case of directional selection acting on a viral protein involved in a host-parasitoid interaction - art. no. 38},
  author = {{S}erbielle, {C}. and {C}howdhury, {S}. and {P}ichon, {S}. and {D}upas, {S}t{\'e}phane and {L}esobre, {J}. and {P}urisima, {E}. {O}. and {D}rezen, {J}. {M}. and {H}uguet, {E}.},
  editor = {},
  language = {{ENG}},
  abstract = {{B}ackground: {I}n pathogens, certain genes encoding proteins that directly interact with host defences coevolve with their host and are subject to positive selection. {I}n the lepidopteran host-wasp parasitoid system, one of the most original strategies developed by the wasps to defeat host defences is the injection of a symbiotic polydnavirus at the same time as the wasp eggs. {T}he virus is essential for wasp parasitism success since viral gene expression alters the immune system and development of the host. {A}s a wasp mutualist symbiont, the virus is expected to exhibit a reduction in genome complexity and evolve under wasp phyletic constraints. {H}owever, as a lepidopteran host pathogenic symbiont, the virus is likely undergoing strong selective pressures for the acquisition of new functions by gene acquisition or duplication. {T}o understand the constraints imposed by this particular system on virus evolution, we studied a polydnavirus gene family encoding cyteine protease inhibitors of the cystatin superfamily. {R}esults: {W}e show that cystatins are the first bracovirus genes proven to be subject to strong positive selection within a host-parasitoid system. {A} generated three-dimensional model of {C}otesia congregata bracovirus cystatin 1 provides a powerful framework to position positively selected residues and reveal that they are concentrated in the vicinity of actives sites which interact with cysteine proteases directly. {I}n addition, phylogenetic analyses reveal two different cystatin forms which evolved under different selective constraints and are characterized by independent adaptive duplication events. {C}onclusion: {P}ositive selection acts to maintain cystatin gene duplications and induces directional divergence presumably to ensure the presence of efficient and adapted cystatin forms. {D}irectional selection has acted on key cystatin active sites, suggesting that cystatins coevolve with their host target. {W}e can strongly suggest that cystatins constitute major virulence factors, as was already proposed in previous functional studies.},
  keywords = {},
  booktitle = {},
  journal = {{B}mc {B}iology},
  volume = {6},
  numero = {},
  pages = {93--97},
  ISSN = {1741-7007},
  year = {2008},
  DOI = {10.1186/1741-7007-6-38},
  URL = {https://www.documentation.ird.fr/hor/{PAR}00003095},
}