Data from: A novel sperm-derived seminal fluid protein in Caenorhabditis nematodes

Nematode sperm contain subcellular vesicles known as membranous organelles
(MOs) that fuse with the sperm cell membrane upon sperm activation to
release their soluble contents into the extracellular space. The second
most abundant proteins in the MOs belong to the conserved
Nematode-Specific Peptide family, group F (NSPF) gene family. We
hypothesize that these proteins contribute to seminal fluid and are part
of post-insemination reproductive tract dynamics. We characterized the
anatomical region where the NSPF proteins likely function during
fertilization using dissected testes and whole-worm immunostaining of a
His-tagged nspf-1 transgene. We confirmed that NSPF proteins are
transferred to females during mating. NSPF proteins localize to the uterus
lumen when transferred to mated females and in unmated adult
hermaphrodites. These results suggest that the uterine localization of the
NSPF proteins is likely a functional property of both male-derived sperm
and self-sperm and not incidental to the point of transfer during mating.
In males, we confirm that NSPF proteins are indeed sperm derived. We then
used experimental evolution to compete the wildtype allele against a
deletion allele in 10 replicate obligate-outcrossing populations. We
calculated a mean selective disadvantage of 0.1% for the deletion allele,
which indicated that the NSPF genes are beneficial to male fitness. This
conclusion was reinforced by qualitative trends from lower-powered
single-generation fertility assays. Together we demonstrate that nematodes
use a novel approach for contributing proteins to seminal fluid and show
that the highly abundant NSPF proteins likely have a beneficial impact on
fitness.

线虫精子中含有被称为膜状细胞器（membranous organelles，MOs）的亚细胞囊泡，该类囊泡会在精子激活时与精子细胞膜融合，将其可溶性内容物释放至细胞外空间。膜状细胞器中丰度位列第二的蛋白质，隶属于保守的线虫特异性肽家族F组（NSPF）基因家族。我们推测，此类蛋白质可参与精浆构成，且属于授精后生殖道动态调控过程的组成部分。我们借助解剖精巢与对携带组氨酸标签（His-tag）的nspf-1转基因个体开展全虫免疫染色的手段，明确了NSPF蛋白质在受精过程中可能发挥功能的解剖学区域。我们证实，NSPF蛋白质可在交配过程中传递至雌性个体体内。当传递至已交配雌性体内时，NSPF蛋白质会定位于子宫腔中；而在未交配的成年雌雄同体体内，此类蛋白质同样呈现该定位模式。上述结果表明，NSPF蛋白质的子宫定位，大概率是雄性来源精子与自体精子共有的功能特性，并非交配过程中传递时的偶然现象。在雄性个体中，我们进一步证实NSPF蛋白质确实源自精子。随后，我们借助实验进化手段，在10个重复的专性异交种群中开展了野生型等位基因与缺失等位基因的竞争实验。我们测算得出，缺失等位基因的平均选择劣势为0.1%，这表明NSPF基因对雄性适合度具有增益作用。统计效力较低的单代生育力实验所得的定性趋势，进一步印证了这一结论。综上，我们证实线虫采用了一种全新的蛋白质投递策略以参与精浆构成，并表明丰度极高的NSPF蛋白质大概率对个体适合度具有积极影响。