Norry Fabian M, Gomez Federico H, Loeschcke Volker
Departamento de Ecología, Genética y Evolución, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, C-1428-EHA, Buenos Aires, Argentina.
Mol Ecol. 2007 Aug;16(15):3274-84. doi: 10.1111/j.1365-294X.2007.03335.x.
In insects, two ecologically relevant traits of thermal adaptation are knockdown resistance to high temperature (KRHT) and chill-coma recovery (CCR). Chromosome 2 of Drosophila melanogaster was tested for quantitative trait loci (QTL) affecting both CCR and KRHT in backcrosses between homosequential lines that are fixed for the standard (noninverted) sequence of this autosome. These lines were obtained by artificial selection on KRHT and subsequent inbreeding from a stock that was derived from a single wild population. Heat-induced expression of the 70KD heat-shock protein (Hsp70) was also examined for variation between the lines. Composite interval mapping was performed for each trait on each reciprocal backcross, identifying one QTL region in the middle of chromosome 2 for both KRHT and CCR. The largest estimates of additive effects were found in pericentromeric regions of chromosome 2, accounting for 10-14% (CCR) and 10-17% (KRHT) of the phenotypic variance in BC populations. No QTL was found in the region of the heat-shock factor (hsf) gene. However, the two parental lines have diverged in the heat-induced Hsp70 expression. Distribution of KRHT QTL on chromosome 2 was similar between this study based on crosses between lines selected from a single wild population and previous work based on crosses between selection lines from different continents. Colocalized QTL showed a trade-off association between CCR and KRHT, which should be the result of either multiple, tightly linked trait-specific genes or a single gene with pleiotropic effects on the traits. We discuss candidate loci contained within the QTL regions.
在昆虫中，热适应性的两个与生态相关的性状是对高温的击倒抗性（KRHT）和冷昏迷恢复能力（CCR）。在黑腹果蝇的2号染色体上检测了影响CCR和KRHT的数量性状基因座（QTL），这些检测是在同源序列品系之间的回交中进行的，这些品系固定了这条常染色体的标准（非倒位）序列。这些品系是通过对KRHT进行人工选择并随后从源自单个野生种群的一个品系中进行近亲繁殖而获得的。还检查了70KD热休克蛋白（Hsp70）的热诱导表达在品系间的差异。对每个互交回交的每个性状进行复合区间作图，在2号染色体中部鉴定出一个同时影响KRHT和CCR的QTL区域。在2号染色体的着丝粒周围区域发现了最大的加性效应估计值，占BC群体表型变异的10 - 14%（CCR）和10 - 17%（KRHT）。在热休克因子（hsf）基因区域未发现QTL。然而，两个亲本品系在热诱导的Hsp70表达上存在差异。基于从单个野生种群中选择的品系之间的杂交进行的这项研究与之前基于来自不同大陆的选择品系之间的杂交所做的工作相比，2号染色体上KRHT QTL的分布相似。共定位的QTL显示CCR和KRHT之间存在权衡关联，这应该是多个紧密连锁的性状特异性基因或一个对这些性状具有多效性的单个基因导致的结果。我们讨论了QTL区域内包含的候选基因座。
