Clark A G, Aguadé M, Prout T, Harshman L G, Langley C H
Department of Biology, Pennsylvania State University, University Park 16802.
Genetics. 1995 Jan;139(1):189-201. doi: 10.1093/genetics/139.1.189.
Genes that influence mating and/or fertilization success may be targets for strong natural selection. If females remate frequently relative to the duration of sperm storage and rate of sperm use, sperm displacement may be an important component of male reproductive success. Although it has long been known that mutant laboratory stocks of Drosophila differ in sperm displacement, the magnitude of the naturally occurring genetic variation in this character has not been systematically quantified. Here we report the results of a screen for variation in sperm displacement among 152 lines of Drosophilia melanogaster that were made homozygous for second and/or third chromosomes recovered from natural populations. Sperm displacement was assayed by scoring the progeny of cn;bw females that had been mated sequentially to cn;bw and tested males in either order. Highly significant differences were seen in both the ability to displace sperm that is resident in the female's reproductive tract and in the ability to resist displacement by subsequent sperm. Most lines exhibited nearly complete displacement, having nearly all progeny sired by the second male, but several lines had as few as half the progeny fathered by the second male. Lines that were identified in the screen for naturally occurring variation in sperm displacement were also characterized for single-strand conformation polymorphisms (SSCP) at seven accessory gland protein (Acp) genes, Glucose dehydrogenase (Gld), and Esterase-6 (Est-6). Acp genes encode proteins that are in some cases known to be transmitted to the female in the seminal fluid and are likely candidates for genes that might mediate the phenomenon of sperm displacement. Significant associations were found between particular Acp alleles at four different loci (Acp26Aa/Ab, Acp29B, Acp36DE and Acp53E) and the ability of males to resist displacement by subsequent sperm. There was no correlation between the ability to displace resident sperm and the ability to resist being displaced by subsequent sperm. This lack of correlation, and the association of Acp alleles with resisting subsequent sperm only, suggests that different mechanisms mediate the two components of sperm displacement.
影响交配和/或受精成功率的基因可能是强大自然选择的目标。如果雌性相对于精子储存时长和精子使用速率而言频繁再次交配，那么精子置换可能是雄性繁殖成功的一个重要组成部分。虽然长期以来已知果蝇的突变实验室品系在精子置换方面存在差异，但这一性状中自然发生的遗传变异程度尚未得到系统量化。在此，我们报告了一项对152个黑腹果蝇品系精子置换变异的筛选结果，这些品系对从自然种群中回收的第二和/或第三条染色体进行了纯合。通过对依次与cn;bw和受试雄性交配的cn;bw雌性的后代进行评分来测定精子置换情况，交配顺序任意。在置换雌性生殖道中驻留精子的能力以及抵抗后续精子置换的能力方面均观察到高度显著的差异。大多数品系表现出几乎完全的置换，几乎所有后代均由第二个雄性所生，但有几个品系由第二个雄性所生的后代少至一半。在筛选中鉴定出的具有自然发生的精子置换变异的品系，还针对七个附属腺蛋白（Acp）基因、葡萄糖脱氢酶（Gld）和酯酶-6（Est-6）的单链构象多态性（SSCP）进行了表征。Acp基因编码的蛋白质在某些情况下已知会通过精液传递给雌性，并且很可能是介导精子置换现象的基因候选者。在四个不同位点（Acp26Aa/Ab、Acp29B、Acp36DE和Acp53E）的特定Acp等位基因与雄性抵抗后续精子置换的能力之间发现了显著关联。置换驻留精子的能力与抵抗被后续精子置换的能力之间没有相关性。这种缺乏相关性以及Acp等位基因仅与抵抗后续精子相关联的情况表明，不同的机制介导了精子置换的两个组成部分。
