Body stiffness is a mechanical property that facilitates contact-mediated mate recognition in Caenorhabditis elegans

C. elegans males optimize mate-preference decisions via sex-specific responses to multimodal sensory cues

For sexually reproducing animals, selecting optimal mates is important for maximizing reproductive fitness. In the nematode C. elegans, populations reproduce largely by hermaphrodite self-fertilization, but the cross-fertilization of hermaphrodites by males also occurs. Males' ability to recognize hermaphrodites involves several sensory cues, but an integrated view of the ways males use these cues in their native context to assess characteristics of potential mates has been elusive. Here, we examine the mate-preference behavior of C. elegans males evoked by natively produced cues. We find that males use a combination of volatile sex pheromones (VSPs), ascaroside sex pheromones, surface-associated cues, and other signals to assess multiple features of potential mates. Specific aspects of mate preference are communicated by distinct signals: developmental stage and sex are signaled by ascaroside pheromones and surface cues, whereas the presence of a self-sperm-depleted hermaphrodite is likely signaled by VSPs. Furthermore, males prefer to interact with virgin over mated, and well-fed over food-deprived, hermaphrodites; these preferences are likely adaptive and are also mediated by ascarosides and other cues. Sex-typical mate-preference behavior depends on the sexual state of the nervous system, such that pan-neuronal genetic masculinization in hermaphrodites generates male-typical social behavior. We also identify an unexpected role for the sex-shared ASH sensory neurons in male attraction to ascaroside sex pheromones. Our findings lead to an integrated view in which the distinct physical properties of various mate-preference cues guide a flexible, stepwise behavioral program by which males assess multiple features of potential mates to optimize mate preference.

Adult-specific collagen COL-19 is dispensable for contact-mediated mate recognition in Caenorhabditis elegans

Mate recognition in C. elegans involves the integration of multiple sensory cues to facilitate the identification of suitable mates for reproductive behaviors. The cuticle, serving as the protective outer layer enveloping the entire body, has been implicated in eliciting contact responses essential for contact-mediated mate recognition in males. However, the specific constituents of cuticular cues have yet to be identified. In this study, we investigate the potential modulatory role of adult-specific collagen COL-19 in contact-mediated mate recognition. Our study shows that the expression of COL-19 ::GFP is adult-specific and not sexually dimorphic. Knockdown of col-19 via RNAi does not affect mate attractiveness of hermaphrodites in male retention assay, as corroborated by generating two independent col-19 putative null mutants via CRISPR/Cas9. These findings suggest that col-19 does not contribute to contact-mediated mate recognition, thereby advancing our mechanistic understanding of the intricate social interactions between sexes in C. elegans .

ADARs regulate cuticle collagen expression and promote survival to pathogen infection

BACKGROUND

In all organisms, the innate immune system defends against pathogens through basal expression of molecules that provide critical barriers to invasion and inducible expression of effectors that combat infection. The adenosine deaminase that act on RNA (ADAR) family of RNA-binding proteins has been reported to influence innate immunity in metazoans. However, studies on the susceptibility of ADAR mutant animals to infection are largely lacking.

RESULTS

Here, by analyzing adr-1 and adr-2 null mutants in well-established slow-killing assays, we find that both Caenorhabditis elegans ADARs are important for organismal survival to gram-negative and gram-positive bacteria, all of which are pathogenic to humans. Furthermore, our high-throughput sequencing and genetic analysis reveal that ADR-1 and ADR-2 function in the same pathway to regulate collagen expression. Consistent with this finding, our scanning electron microscopy studies indicate adr-1;adr-2 mutant animals also have altered cuticle morphology prior to pathogen exposure.

CONCLUSIONS

Our data uncover a critical role of the C. elegans ADAR family of RNA-binding proteins in promoting cuticular collagen expression, which represents a new post-transcriptional regulatory node that influences the extracellular matrix. In addition, we provide the first evidence that ADAR mutant animals have altered susceptibility to infection with several opportunistic human pathogens, suggesting a broader role of ADARs in altering physical barriers to infection to influence innate immunity.

C. elegans Hedgehog-related proteins are tissue- and substructure-specific components of the cuticle and pre-cuticle

In C. elegans, divergent Hedgehog-related (Hh-r) and Patched-related (PTR) proteins promote numerous processes ranging from epithelial and sense organ development to pathogen responses to cuticle shedding during the molt cycle. Here we show that Hh-r proteins are actual components of the cuticle and pre-cuticle apical extracellular matrices (aECMs) that coat, shape, and protect external epithelia. Different Hh-r proteins stably associate with the aECMs of specific tissues and with specific substructures such as furrows and alae. Hh-r mutations can disrupt matrix structure. These results provide a unifying model for the function of nematode Hh-r proteins and highlight ancient connections between Hh proteins and the extracellular matrix.