Norry Fabian M, Scannapieco Alejandra C, Sambucetti Pablo, Bertoli Carlos I, 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. 2008 Oct;17(20):4570-81. doi: 10.1111/j.1365-294X.2008.03945.x.
The thermotolerance effect of heat hardening (also called short-term acclimation), knockdown resistance to high temperature (KRHT) with and without heat hardening and chill-coma recovery (CCR) are important phenotypes of thermal adaptation in insects and other organisms. Drosophila melanogaster from Denmark and Australia were previously selected for low and high KRHT, respectively. These flies were crossed to construct recombinant inbred lines (RIL). KRHT was higher in heat-hardened than in nonhardened RIL. We quantify the heat-hardening effect (HHE) as the ratio in KRHT between heat-hardened and nonhardened RIL. Composite interval mapping revealed a more complex genetic architecture for KRHT without heat-hardening than for KRHT in heat-hardened insects. Five quantitative trait loci (QTL) were found for KRHT, but only two of them were significant after heat hardening. KRHT and CCR showed trade-off associations for QTL both in the middle of chromosome 2 and the right arm of chromosome 3, which should be the result of either pleiotropy or linkage. The major QTL on chromosome 2 explained 18% and 27-33% of the phenotypic variance in CCR and KRHT in nonhardened flies, respectively, but its KRHT effects decreased by heat hardening. We discuss candidate loci for each QTL. One HHE-QTL was found in the region of small heat-shock protein genes. However, HHE-QTL explained only a small fraction of the phenotypic variance. Most heat-resistance QTL did not colocalize with CCR-QTL. Large-effect QTL for CCR and KRHT without hardening (basal thermotolerance) were consistent across continents, with apparent transgressive segregation for CCR. HHE (inducible thermotolerance) was not regulated by large-effect QTL.
热硬化（也称为短期驯化）的耐热性效应、有无热硬化情况下的高温击倒抗性（KRHT）以及冷昏迷恢复（CCR）是昆虫和其他生物体热适应的重要表型。先前分别从丹麦和澳大利亚选取了黑腹果蝇，对其进行低KRHT和高KRHT的选育。将这些果蝇进行杂交以构建重组自交系（RIL）。热硬化的RIL的KRHT高于未硬化的RIL。我们将热硬化效应（HHE）量化为热硬化RIL与未硬化RIL的KRHT之比。复合区间作图显示，未进行热硬化时KRHT的遗传结构比热硬化昆虫中KRHT的遗传结构更为复杂。发现了5个与KRHT相关的数量性状位点（QTL），但热硬化后只有其中2个显著。在2号染色体中部和3号染色体右臂上，KRHT和CCR的QTL表现出权衡关联，这应该是多效性或连锁的结果。2号染色体上的主要QTL分别解释了未硬化果蝇CCR和KRHT表型变异的18%以及27 - 33%，但其对KRHT的影响在热硬化后降低。我们讨论了每个QTL的候选基因座。在小热休克蛋白基因区域发现了一个HHE - QTL。然而，HHE - QTL仅解释了一小部分表型变异。大多数耐热QTL与CCR - QTL并不共定位。未硬化时（基础耐热性）CCR和KRHT的大效应QTL在各大洲是一致的，CCR存在明显的超亲分离。HHE（诱导性耐热性）不受大效应QTL的调控。
