Environmental change has a detrimental effect on species survival, but the mechanisms are not well understood. We recently delineated a neuroendocrine mechanism in C. elegans hermaphrodites that couples environmental cues, such as ascarosides to sperm motility behavior in the uterus (1). In nutritionally rich, less crowded environments, amphid sensory neurons secrete DAF-7 TGF-β to stimulate synthesis of ovarian F-series prostaglandins, which guide sperm to the spermatheca. Conventional wisdom is that males maximize reproductive output through production of copious competitive sperm, independent of environment. Here we overturn this dogma. We identify at least four evolutionarily related chemosensory receptors that are essential in males to generate sperm capable of efficiently navigating the hermaphrodite reproductive tract. These chemoreceptors, which include srb-13, srb-16, and srb-5 are physically clustered in a 22 kilobase genomic region, together with four other srb family members. Extensive genome-editing and transgenic manipulations show that srb chemoreceptors function in head sensory neurons, such as amphids. We identify at least two parallel pathways that likely converge on the Gα subunit GOA-1 to modulate spermatogenic gene expression from sperm nuclear and mitochondrial genomes. These pathways affect sperm motility responses (i.e. to prostaglandins) and competitiveness, but not spermatid size, activation, or fertilization ability, per se. Global RNA sequencing analysis suggests that SRB pathways also impact male metabolism and immunity, consistent with complex tradeoffs at the organismal level. SRB signaling is independent of food and DAF-7 activity, indicating that males and hermaphrodites respond to distinct environmental cues. Together, our results show that environment has a profound impact on sperm function, with each sex manipulating sperm motility properties, presumably to optimize their own reproductive success.
(1) McKnight et al. 2014. Neurosensory perception of environmental cues regulates sperm motility critical for fertilization. Science, 344:754-757.
Please note: Abstract shown here should NOT be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.
The Genetics Society of America
9650 Rockville Pike, Bethesda, MD
Phone: 301-634-7300, Fax: 301-634-7079
Questions and Comments: email@example.com