van Diepeningen Anne D, Pál Károly, van der Lee Theo A J, Hoekstra Rolf F, Debets Alfons J M
Laboratory of Genetics, Department of Plant Sciences, Wageningen University, Arboretumlaan 4, 6703 BD Wageningen, The Netherlands.
Mycol Res. 2009 Feb;113(Pt 2):222-9. doi: 10.1016/j.mycres.2008.10.003. Epub 2008 Oct 26.
Heterokaryon incompatibility among Aspergillus niger strains is a widespread phenomenon that is observed as the inability to form stable heterokaryons. The genetic basis of heterokaryon incompatibility reactions is well established in some sexual filamentous fungi but largely unknown in presumed asexual species, such as A. niger. To test whether the genes that determine heterokaryon incompatibility in Neurospora crassa, such as het-c, vib-1 and pin-c, have a similar function in A. niger, we performed a short in silico search for homologues of these genes in the A. niger and several related genomes. For het-c, pin-c and vib-1 we did indeed identify putative orthologues. We then screened a genetically diverse worldwide collection of incompatible black Aspergilli for polymorphisms in the het-c orthologue. No size variation was observed in the variable het-c indel region that determines the specificity in N. crassa. Sequence comparison showed only minor variation in the number of glutamine coding triplets. However, introduction of one of the three N. crassa alleles (het-c2) in A. niger by transformation resulted in an abortive phenotype, reminiscent of the heterokaryon incompatibility in N. crassa. We conclude that although the genes required are present and the het-c homologue could potentially function as a heterokaryon incompatibility gene, het-c has no direct function in heterokaryon incompatibility in A. niger because the necessary allelic variation is absent.
黑曲霉菌株间的异核体不相容性是一种普遍现象，表现为无法形成稳定的异核体。异核体不相容反应的遗传基础在一些有性丝状真菌中已得到充分确立，但在假定的无性物种（如黑曲霉）中却 largely unknown。为了测试在粗糙脉孢菌中决定异核体不相容性的基因（如het-c、vib-1和pin-c）在黑曲霉中是否具有类似功能，我们在黑曲霉和几个相关基因组中对这些基因的同源物进行了简短的电子搜索。对于het-c、pin-c和vib-1，我们确实鉴定出了假定的直系同源物。然后，我们在全球范围内收集的遗传多样的不相容黑色曲霉中筛选het-c直系同源物的多态性。在决定粗糙脉孢菌特异性的可变het-c插入缺失区域未观察到大小变异。序列比较显示谷氨酰胺编码三联体数量只有微小变异。然而，通过转化将粗糙脉孢菌的三个等位基因之一（het-c2）引入黑曲霉会导致流产表型，这让人联想到粗糙脉孢菌中的异核体不相容性。我们得出结论，尽管所需基因存在且het-c同源物可能潜在地作为异核体不相容基因发挥作用，但het-c在黑曲霉的异核体不相容性中没有直接功能，因为缺乏必要的等位基因变异。
