Fox C W, Stillwell R C
Department of Entomology, University of Kentucky, Lexington, KY 40546-0091, USA.
Heredity (Edinb). 2009 Jul;103(1):62-72. doi: 10.1038/hdy.2009.31. Epub 2009 Apr 1.
We have little understanding of how environmental conditions affect the expression of the genetic load for lifespan and adult mortality rates, or how this environmental dependence affect tests of models for the evolution of senescence. We use the seed-feeding beetle, Callosobruchus maculatus, as a model to explore how the inbreeding load (L) affecting adult lifespan varies with rearing conditions (diet and temperature), and how rearing conditions affect tests of the mutation accumulation model of senescence. When reared under benign conditions, there was a large sex difference in inbreeding depression (delta) and the inbreeding load (L=0.51-0.86 lethal equivalents per gamete for females L= approximately 0 for males). This sex difference in L was dependent on temperature, but not on rearing host or heat shock. At both high and low temperatures (relative to intermediate temperature) L increased for males, and L converged for the sexes at low temperature (L=0.26-0.53 for both sexes). Correlations were small for L between pairs of temperatures, indicating that the genes responsible for the inbreeding load differed between temperatures. In contrast to predictions of the mutation accumulation model of senescence, the age-specific inbreeding load for the adult mortality rate (L(u(t))) did not increase with age in any rearing environment. The genetic load underlying lifespan and adult mortality rates, and large sex differences in the genetic load, is highly dependent on environmental conditions. Estimating the genetic load in benign laboratory environments may be insufficient to predict the genetics underlying lifespan variation in nature where environmental variation is the norm.
我们对环境条件如何影响寿命的遗传负荷表达和成年死亡率，或者这种环境依赖性如何影响衰老进化模型的检验知之甚少。我们以食籽甲虫Callosobruchus maculatus为模型，探讨影响成年寿命的近亲繁殖负荷（L）如何随饲养条件（饮食和温度）而变化，以及饲养条件如何影响衰老的突变积累模型的检验。在良性条件下饲养时，近亲繁殖衰退（δ）存在很大的性别差异，且近亲繁殖负荷（雌性为每个配子0.51 - 0.86个致死当量，雄性约为0）。L的这种性别差异取决于温度，但不取决于饲养宿主或热休克。在高温和低温（相对于中间温度）下，雄性的L均增加，在低温下两性的L趋于一致（两性均为0.26 - 0.53）。不同温度对之间L的相关性较小，表明负责近亲繁殖负荷的基因在不同温度下有所不同。与衰老的突变积累模型的预测相反，成年死亡率的年龄特异性近亲繁殖负荷（L(u(t))）在任何饲养环境中均未随年龄增加。寿命和成年死亡率背后的遗传负荷以及遗传负荷中的巨大性别差异高度依赖于环境条件。在良性实验室环境中估计遗传负荷可能不足以预测自然环境中寿命变化背后的遗传学，因为环境变化在自然环境中是常态。
