Dick Kenneth B, Ross Chelsea R, Yampolsky Lev Y
Department of Biological Sciences, East Tennessee State University, Johnson City, TN 37614-1710, USA.
Genet Res (Camb). 2011 Aug;93(4):265-73. doi: 10.1017/S001667231100019X. Epub 2011 Jul 18.
We measure genetic variation in lifespan and fecundity at two food levels in 34 core lines of the Drosophila Genetic Reference Panel collection. Lines were significantly different from each other in lifespan and fecundity at both restricted and full food. There was a strong food-by-line interaction for the slope of age-specific mortality, fecundity and proportion of fertilized eggs, indicating the presence of genetic variation for the strength of the dietary restriction effect, likely to represent standing genetic variation in a natural population from which the lines used have originated. No trade-off between fecundity and lifespan manifested in life-history variation among inbred lines. Our data partially corroborate the recent proposition that availability of nutrient-free water eliminates the apparent dietary restriction at least in some conditions. Although flies on full food with water added had lifespan slightly higher than those without a water source, it was still significantly lower than that in flies on restricted food, with no indication of interaction. We fully corroborate the recently discovered effect of addition of essential amino acids to the medium: addition of 1.5 mM methionine to restricted food significantly increased fecundity without a measurable decrease in lifespan; addition of each of 10 essential amino acids increased fecundity and decreased females lifespan to the levels observed on full food, again with no evidence of line-by-food interactions. We propose a mechanistic hypothesis explaining the observed data, based on the assumption that food consumption by flies is adjusted according to flies' saturation in water and methionine.
我们在果蝇遗传参考面板收集的34个核心品系中，于两种食物水平下测量了寿命和繁殖力的遗传变异。在受限食物和充足食物条件下，品系之间在寿命和繁殖力方面均存在显著差异。对于特定年龄死亡率、繁殖力和受精卵比例的斜率，存在强烈的食物与品系间的相互作用，这表明存在饮食限制效应强度的遗传变异，可能代表了所用品系起源的自然种群中的现存遗传变异。在近交系的生活史变异中，繁殖力和寿命之间未表现出权衡关系。我们的数据部分证实了最近的一个观点，即无营养水的可获得性至少在某些条件下消除了明显的饮食限制。尽管在充足食物中添加水的果蝇寿命略高于没有水源的果蝇，但仍显著低于受限食物条件下果蝇的寿命，且没有相互作用的迹象。我们完全证实了最近发现的向培养基中添加必需氨基酸的效应：向受限食物中添加1.5 mM甲硫氨酸可显著提高繁殖力，且寿命没有可测量的降低；添加10种必需氨基酸中的每一种都会提高繁殖力，并使雌性果蝇的寿命降至在充足食物条件下观察到的水平，同样没有品系与食物相互作用的证据。我们基于果蝇根据其对水和甲硫氨酸的饱和度来调整食物摄入量这一假设，提出了一个解释所观察数据的机制假说。
