Southern Regional Research Center, Agricultural Research Service, U. S. Department of Agriculture, 1100 Robert E. Lee Boulevard, New Orleans, LA, 70124, USA.
Appl Microbiol Biotechnol. 2019 Jun;103(12):4889-4897. doi: 10.1007/s00253-019-09820-0. Epub 2019 Apr 29.
Conidia are asexual spores and play a crucial role in fungal dissemination. Conidial pigmentation is important for tolerance against UV radiation and contributes to survival of fungi. The molecular basis of conidial pigmentation has been studied in several fungal species. In spite of sharing the initial common step of polyketide formation, other steps for pigment biosynthesis appear to be species-dependent. In this study, we isolated an Aspergillus flavus spontaneous mutant that produced yellow conidia. The underlying genetic defect, a three-nucleotide in-frame deletion in the gene, AFLA_051390, that encodes a copper-transporting ATPase, was identified by a comparative genomics approach. This genetic association was confirmed by disruption of the wild-type gene. When yellow mutants were grown on medium supplemented with copper ions or chloride ions, green conidial color was partially and nearly completely restored, respectively. Further disruption of AFLA_045660, an orthologue of Aspergillus nidulans yA (yellow pigment) that encodes a multicopper oxidase, in wild type and a derived strain producing dark green conidia showed that it yielded mutants that produced gold conidia. The results placed formation of the gold pigment after that of the yellow pigment and before that of the dark green pigment. Using reported inhibitors of DHN-melanin (tricyclazole and phthalide) and DOPA-melanin (tropolone and kojic acid) pathways on a set of conidial color mutants, we investigated the involvement of melanin biosynthesis in A. flavus conidial pigment formation. Results imply that both pathways have no bearing on conidial pigment biosynthesis of A. flavus.
分生孢子是无性孢子，在真菌传播中起着至关重要的作用。分生孢子的色素沉着对于耐受紫外线辐射很重要，并有助于真菌的存活。已经在几种真菌物种中研究了分生孢子色素形成的分子基础。尽管它们共享聚酮形成的初始共同步骤，但其他色素生物合成步骤似乎取决于物种。在这项研究中，我们分离到一个产黄色分生孢子的黄曲霉自发突变体。通过比较基因组学方法，鉴定出该突变体的潜在遗传缺陷是 AFLA_051390 基因中的三个核苷酸框内缺失，该基因编码铜转运 ATP 酶。通过野生型基因的破坏证实了这种遗传关联。当黄色突变体在补充铜离子或氯离子的培养基上生长时，绿色分生孢子颜色分别部分和几乎完全恢复。野生型和产生深绿色分生孢子的衍生菌株中进一步破坏 Aspergillus nidulans yA（黄色色素）的同源物 AFLA_045660，该基因编码多铜氧化酶，表明它产生了产生金黄色分生孢子的突变体。结果表明，金黄色色素的形成先于黄色色素，后于深绿色色素。使用已报道的 DHN-黑色素（三唑和邻苯二甲酸酐）和 DOPA-黑色素（曲酸和 kojic 酸）途径抑制剂在一组分生孢子颜色突变体上，我们研究了黑色素生物合成在黄曲霉分生孢子色素形成中的作用。结果表明，这两种途径都与黄曲霉分生孢子色素的生物合成无关。
