Covert S F
Daniel B. Warnell School of Forest Resources, University of Georgia, Athens, GA 30602-2152, USA.
Curr Genet. 1998 May;33(5):311-9. doi: 10.1007/s002940050342.
Within a fungal species, a subset of individuals may have more than the minimal complement of chromosomes. If the extra chromosomes are composed primarily of DNA not found in all representatives of the species, they are most appropriately referred to as supernumerary chromosomes. The patterns of repeated DNA sequences on certain supernumerary chromosomes suggest that they have a different evolutionary history from the essential chromosomes in the same genome. Supernumerary chromosomes can carry functional genes and, in at least two fungal species, genes on such chromosomes play important roles in host-pathogen interactions. Supernumerary chromosomes that confer an adaptive advantage in certain habitats, such as the ability to cause disease on a specific host, may be referred to as "conditionally dispensable" chromosomes in order to reflect their importance in some, but not all, growth conditions. In addition to describing the structural and functional characteristics of known supernumerary chromosomes in fungi, this review discusses the relative merits of the terms that have been used to describe them, and establishes experimental criteria for their identification.
在一个真菌物种内，一部分个体可能拥有超过染色体最小互补数目的染色体。如果额外的染色体主要由该物种所有代表个体中未发现的DNA组成，那么它们最恰当地被称为超数染色体。某些超数染色体上重复DNA序列的模式表明，它们与同一基因组中的必需染色体有着不同的进化历史。超数染色体可以携带功能基因，并且在至少两种真菌物种中，这类染色体上的基因在宿主与病原体的相互作用中发挥着重要作用。在某些生境中赋予适应性优势的超数染色体，比如在特定宿主上引发疾病的能力，可能被称为“条件性可有可无”染色体，以便反映它们在某些而非所有生长条件下的重要性。除了描述真菌中已知超数染色体的结构和功能特征外，本综述还讨论了用于描述它们的术语的相对优点，并确立了识别它们的实验标准。
