Morgan T J, Mackay T F C
Department of Genetics, North Carolina State University, Campus Box 7614, Raleigh, NC 27695-7414, USA.
Heredity (Edinb). 2006 Mar;96(3):232-42. doi: 10.1038/sj.hdy.6800786.
For insects, temperature is a major environmental variable that can influence an individual's behavioral activities and fitness. Drosophila melanogaster is a cosmopolitan species that has had great success in adapting to and colonizing diverse thermal niches. This adaptation and colonization has resulted in complex patterns of genetic variation in thermotolerance phenotypes in nature. Although extensive work has been conducted documenting patterns of genetic variation, substantially less is known about the genomic regions or genes that underlie this ecologically and evolutionarily important genetic variation. To begin to understand and identify the genes controlling thermotolerance phenotypes, we have used a mapping population of recombinant inbred (RI) lines to map quantitative trait loci (QTL) that affect variation in both heat- and cold-stress resistance. The mapping population was derived from a cross between two lines of D. melanogaster (Oregon-R and 2b) that were not selected for thermotolerance phenotypes, but exhibit significant genetic divergence for both phenotypes. Using a design in which each RI line was backcrossed to both parental lines, we mapped seven QTL affecting thermotolerance on the second and third chromosomes. Three of the QTL influence cold-stress resistance and four affect heat-stress resistance. Most of the QTL were trait or sex specific, suggesting that overlapping but generally unique genetic architectures underlie resistance to low- and high-temperature extremes. Each QTL explained between 5 and 14% of the genetic variance among lines, and degrees of dominance ranged from completely additive to partial dominance. Potential thermotolerance candidate loci contained within our QTL regions are identified and discussed.
对于昆虫而言，温度是一个主要的环境变量，它能够影响个体的行为活动和适应性。黑腹果蝇是一种世界性物种，在适应和定殖于多样的热生态位方面取得了巨大成功。这种适应和定殖导致了自然界中耐热性表型复杂的遗传变异模式。尽管已经开展了大量工作记录遗传变异模式，但对于构成这种具有生态和进化重要性的遗传变异基础的基因组区域或基因，人们了解得还非常少。为了开始理解和鉴定控制耐热性表型的基因，我们使用了一个重组近交（RI）系的作图群体来定位影响耐热性和耐寒性变异的数量性状基因座（QTL）。该作图群体源自黑腹果蝇的两个品系（俄勒冈-R和2b）之间的杂交，这两个品系并未针对耐热性表型进行选择，但在这两种表型上都表现出显著的遗传差异。通过将每个RI系与两个亲本系回交的设计，我们在第二和第三条染色体上定位了七个影响耐热性的QTL。其中三个QTL影响耐寒性，四个影响耐热性。大多数QTL是性状或性别特异性的，这表明对低温和高温极端抗性的遗传结构存在重叠但通常是独特的情况。每个QTL解释了品系间5%至14%的遗传变异，显性程度范围从完全加性到部分显性。我们鉴定并讨论了在我们的QTL区域内包含的潜在耐热性候选基因座。
