Imitate to integrate: reviewing the pathway for B chromosome integration in Trypoxylon (Trypargilum) albitarse (Hymenoptera, Sphecidae).
B chromosomes are genomic "intruders" normally characterized by their total dispensability counteracted by a variety of drive mechanisms, which assures their presence regardless of their harmful effects on the host genome. From an evolutionary standpoint, the relationship between standard (A) and B chromosomes can go through different pathways, from an everlasting arms race to a cordial B integration. Examples underlying the first situation are fairly common; B integration, however, has been more a theoretical than a practical possibility. The B chromosome in the haplodiploid solitary wasp Trypoxylon albitarse is probably the first example of a "mimetic" B, which is being integrated into the A genome by limiting itself to one B per haploid genome, the same dosage as the A chromosomes. Here we review some of the findings underlying this hypothesis and discuss the T. albitarse B strategy as a possible mechanism for B chromosome integration as a regular member of the chromosome complement in haplodiploid organisms.
Creighton University, Department of Biomedical Sciences, Omaha, NE 68178, USA. ssanchez@creighton.edu
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D000818:Animals; D002875:Chromosomes / Q000235:genetics*; D016678:Genome; D018716:Molecular Mimicry; D014863:Wasps / Q000235:genetics*