PDF(Pubmed)
Abstract：
Wild-type Aspergillus nidulans asexual spores (conidia) are green due to a pigment that protects the spores against ultraviolet light. The pigment is produced by a biosynthetic pathway, the genes of which are dispersed in the genome. The backbone molecule of the pigment is a polyketide synthesized by a polyketide synthase encoded by the wA gene. If wA is not functional, the conidia are white. The polyketide is modified by a laccase encoded by the yA gene and inactivation of yA in an otherwise wild-type background results in yellow spores. Additional spore color mutations have been isolated and mapped to a locus genetically, but the genes that correspond to these loci have not been determined. Spore color markers have been useful historically, and they remain valuable in the molecular genetics era. One can determine if a transforming fragment has been successfully integrated at the wA or yA locus by simply looking at the color of transformant conidia. The genes of the potentially useful color loci chaA (chartreuse conidia) and fwA (fawn conidia) have not been identified previously. We chose a set of candidate genes for each locus by comparing the assembled genome with the genetic map. By systematically deleting these candidate genes, we identified a cytochrome P450 gene (AN10028) corresponding to chaA. Deletions of this gene result in chartreuse conidia and chartreuse mutations can be complemented in trans by a functional copy of this gene. With fwA, we found that the existing fawn mutation, fwA1, is a deletion of 2241 base pairs that inactivates three genes. By deleting each of these genes, we determined that fwA is AN1088, an EthD domain protein. Deletion of AN1088 results in fawn conidia as expected. Neither deletion of chaA nor fwA restricts growth and both should be valuable target loci for transformations. Combinations of deletions have allowed us to investigate the epistasis relationships of wA, yA, chaA and fwA.
摘要：
野生型构巢曲霉无性孢子（分生孢子）是绿色的，因为它具有保护孢子免受紫外线照射的色素。色素是通过生物合成途径产生的，其基因分散在基因组中。色素的主链分子是由wA基因编码的聚酮化合物合酶合成的聚酮化合物。如果wA不起作用，分生孢子是白色的。聚酮化合物被yA基因编码的漆酶修饰,并且在其它野生型背景中yA的失活导致黄色孢子。其他孢子颜色突变已被分离并遗传定位到一个基因座，但是与这些基因座相对应的基因尚未确定。孢子颜色标记在历史上很有用，它们在分子遗传学时代仍然很有价值。人们可以通过简单地观察转化体分生孢子的颜色来确定转化片段是否已经成功地整合在wA或yA基因座上。先前尚未鉴定出潜在有用的颜色基因座chaA（黄褐色分生孢子）和fwA（小鹿分生孢子）的基因。我们通过将组装的基因组与遗传图谱进行比较，为每个基因座选择了一组候选基因。通过系统地删除这些候选基因，我们确定了对应于chaA的细胞色素P450基因（AN10028）。该基因的缺失会导致黄褐色分生孢子，而黄褐色突变可以通过该基因的功能拷贝进行反式补充。有了fwA,我们发现现有的小鹿突变，fwA1是使三个基因失活的2241个碱基对的缺失。通过删除这些基因中的每一个，我们确定fwA是AN1088，一种EthD结构域蛋白。删除AN1088会产生预期的小鹿分生孢子。chaA和fwA的缺失都不会限制生长，并且两者都应该是转化的有价值的目标基因座。缺失的组合使我们能够研究wA的上位性关系，YA,chaa和fwa.
