Two Doublesex1 mutants revealed a tunable gene network underlying intersexuality in Daphnia magna

Abstract

In recent years, the binary definition of sex is being challenged by repetitive reports about individuals with ambiguous sexual identity from various animal groups. This has created an urge to decode the molecular mechanism underlying sexual development. However, sexual ambiguities are extremely uncommon in nature, limiting their experimental value. Here, we report the establishment of a genetically modified clone of Daphnia magna from which intersex daphniids can be readily generated. By mutating the conserved central sex determining factor Doublesex1, body-wide feminization of male daphniid could be achieved. Comparative transcriptomic analysis also revealed a genetic network correlated with Doublesex1 activity which may account for the establishment of sexual identity in D. magna. We found that Dsx1 repressed genes related to growth and promoted genes related to signaling. We infer that different intersex phenotypes are the results of fluctuation in activity of these Dsx1 downstream factors. Our results demonstrated that the D. magna genome is capable of expressing sex in a continuous array, supporting the idea that sex is actually a spectrum.

Sense-overlapping lncRNA as a decoy of translational repressor protein for dimorphic gene expression

“…However, due to stochasticity in gene expression [ 11 , 12 ], there would be the noise in gene expression. In a previous study, we proved that improper expression of Dsx1 changes the expression profile of its downstream genes resulting in intersex [ 13 ]; which suggested that the stochastic transcription of Dsx1 causing population heterogeneity, should be avoided. In the presence of the Shep, the Dsx1 mRNA from the transcriptional noise cannot be translated immediately because of the binding of the Shep at the TGE-like motif.…”

Regulation of Doublesex1 Expression for Environmental Sex Determination in the Cladoceran Crustacean Daphnia

“…Phenotyping of the Dsx1 mutants Line A and Line B aforementioned also showed Dsx1 dependency of male trait development ( Figure 4 ) ( Nong et al, 2017 ; Nong et al, 2020 ). Compared to Line B males, Line A males showed more severe feminization throughout development, which were obvious in the first antennae and carapace ( Figure 9A ).…”

“…Both lines have a single copy of the mCherry reporter on one of the Dsx1 alleles. In Line A, another Dsx1 allele is mutated with a 6-bp deletion at the start codon, which suggests that this line does not produce any intact Dsx1 protein ( Nong et al, 2020 ). In contrast, Line B has a wild-type Dsx1 gene on another allele.…”

“…Live imaging of mCherry fluorescence in Line B male embryos revealed the dynamic change of spatial expression patterns in early embryos ( Nong et al, 2020 ) ( Figure 6 ). During the initiation phase of Dsx1 , no clear mCherry signal was detected probably due to low Dsx1 expression levels ( Figure 6 , stage i and ii).…”

“…The expression of Dsx1 in these male-specific traits stably continued until the fourth instar stage ( Figure 7 , instar 4). After males showed secondary sex characteristics at the instar 5, mCherry fluorescence expanded to the other several male-specific structures, including the carapace edge below the helmet, the tip of the penis, and the skeletal muscle ( Figure 7 , instar 7) ( Nong et al, 2020 ). These imaging results suggest that Dsx1 is tightly regulated by time and place for controlling male development.…”