Swiss Federal Research Institute WSL, Zürcherstrasse 111, CH-8903 Birmensdorf, Switzerland.
Laboratory of Evolutionary Genetics, Institute of Biology, University of Neuchâtel, Rue Emile-Argand 11, CH-2000 Neuchâtel, Switzerland.
Fungal Genet Biol. 2017 Nov;108:44-54. doi: 10.1016/j.fgb.2017.08.007. Epub 2017 Aug 30.
Filamentous fungi exhibit a broad spectrum of heritable growth patterns and morphological variations reflecting the adaptation of the different species to distinct ecological niches. But also within species, isolates show considerable variation in growth rates and other morphological characteristics. The genetic basis of this intraspecific variation in mycelial growth and morphology is currently poorly understood. By chance, a growth mutant in the root rot pathogen Armillaria ostoyae was discovered. The mutant phenotype was characterized by extremely compact and slow growth, as well as shorter aerial hyphae and hyphal compartments in comparison to the wildtype phenotype. Genetic analysis revealed that the abnormal phenotype is caused by a recessive mutation, which segregates asa single locus in sexual crosses. In order to identify the genetic basis of the mutant phenotype, we performed a quantitative trait locus (QTL) analysis. A mapping population of 198 haploid progeny was genotyped at 11,700 genome-wide single nucleotide polymorphisms (SNPs) making use of double digest restriction site associated DNA sequencing (ddRADseq). In accordance with the genetic analysis, a single significant QTL was identified for the abnormal growth phenotype. The QTL confidence interval spans a narrow, gene dense region of 87kb in the A. ostoyae genome which contains 37 genes. Overall, our study reports the first high-density genetic map for an Armillaria species and shows its successful application in forward genetics by resolving the genetic basis of a mutant phenotype with a severe defect in hyphal growth.
丝状真菌表现出广泛的遗传生长模式和形态变化，反映了不同物种对不同生态位的适应。但即使在同一物种内，分离株的生长速度和其他形态特征也存在很大差异。这种菌丝生长和形态的种内变异的遗传基础目前还知之甚少。偶然间，发现了一种根腐病病原体蜜环菌的生长突变体。该突变体的表型特征是极其紧凑和缓慢的生长，以及与野生型表型相比，气生菌丝和菌丝隔室较短。遗传分析表明，异常表型是由隐性突变引起的，该突变在有性杂交中作为一个单基因座分离。为了确定突变体表型的遗传基础，我们进行了数量性状位点（QTL）分析。利用双酶切限制位点相关 DNA 测序（ddRADseq），在 11700 个全基因组单核苷酸多态性（SNP）上对 198 个单倍体后代的作图群体进行了基因型分析。与遗传分析一致，一个显著的 QTL 被确定为异常生长表型。QTL 置信区间跨越蜜环菌基因组中一个狭窄的、基因密集的 87kb 区域，其中包含 37 个基因。总的来说，我们的研究报告了第一个用于蜜环菌种的高密度遗传图谱，并通过解决菌丝生长严重缺陷的突变体表型的遗传基础，展示了其在正向遗传学中的成功应用。
