Data from: QTL mapping of temperature sensitivity reveals candidate genes for thermal adaptation and growth morphology in the plant pathogenic fungus Zymoseptoria tritici

Different thermal environments impose strong, differential selection on populations, leading to local adaptation, but the genetic basis of thermal adaptation is poorly understood. We used quantitative trait locus (QTL) mapping in the fungal wheat pathogen Zymoseptoria tritici to study the genetic architecture of thermal adaptation and identify candidate genes. Four wild-type strains originating from the same thermal environment were crossed to generate two mapping populations with 263 (cross 1) and 261 (cross 2) progeny. Restriction site-associated DNA sequencing was used to genotype 9745 (cross 1) and 7333 (cross 2) single-nucleotide polymorphism markers segregating within the mapping population. Temperature sensitivity was assessed using digital image analysis of colonies growing at two different temperatures. We identified four QTLs for temperature sensitivity, with unique QTLs found in each cross. One QTL had a logarithm of odds score >11 and contained only six candidate genes, including PBS2, encoding a mitogen-activated protein kinase kinase associated with low temperature tolerance in Saccharomyces cerevisiae. This and other QTLs showed evidence for pleiotropy among growth rate, melanization and growth morphology, suggesting that many traits can be correlated with thermal adaptation in fungi. Higher temperatures were highly correlated with a shift to filamentous growth among the progeny in both crosses. We show that thermal adaptation has a complex genetic architecture, with natural populations of Z. tritici harboring significant genetic variation for this trait. We conclude that Z. tritici populations have the potential to adapt rapidly to climate change and expand into new climatic zones.

不同的热环境会对种群施加强烈的差异化选择压力，进而导致局部适应，但目前学界对热适应的遗传基础仍知之甚少。本研究以小麦病原真菌小麦颖枯病菌（Zymoseptoria tritici）为研究对象，通过数量性状位点（quantitative trait locus, QTL）定位技术，解析热适应的遗传结构并筛选候选基因。我们选取源自同一热环境的4株野生型菌株进行杂交，构建了两个遗传作图群体：杂交组合1包含263个子代菌株，杂交组合2包含261个子代菌株。采用限制性酶切位点相关DNA测序（restriction site-associated DNA sequencing, RAD-seq）技术对两个群体进行基因分型，其中杂交组合1共获得9745个分离的单核苷酸多态性（single-nucleotide polymorphism, SNP）标记，杂交组合2共获得7333个分离的单核苷酸多态性标记。通过对两种不同温度下培养的菌落进行数字图像分析，量化评估菌株的温度敏感性。本研究共检测到4个与温度敏感性相关的QTL，且两个杂交组合分别拥有独特的QTL。其中1个QTL的似然比对数（logarithm of odds, LOD）分值大于11，仅包含6个候选基因，包括PBS2基因——该基因编码一种丝裂原活化蛋白激酶激酶（mitogen-activated protein kinase kinase, MAPKK），在酿酒酵母（Saccharomyces cerevisiae）中该激酶与低温耐受性相关。该QTL与其他QTL均表现出对生长速率、黑色素化及生长形态的多效性调控迹象，这表明真菌的诸多性状均可能与热适应存在关联。在两个杂交组合的子代中，较高的培养温度均与菌丝状生长的转变呈现显著相关性。本研究证实，热适应具有复杂的遗传结构，小麦颖枯病菌的自然种群中存在与该性状相关的大量遗传变异。综上，小麦颖枯病菌种群具备快速适应气候变化并拓展至新气候区域的演化潜力。