Ovotestes suggest cryptic genetic influence in a reptile model for temperature-dependent sex determination

Whiteley, Sarah L.; Georges, Arthur; Weisbecker, Vera; Schwanz, Lisa E.; Holleley, Clare E.

doi:10.1098/rspb.2020.2819

Cited by 14 publications

(15 citation statements)

References 58 publications

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“…Despite being considered a TSD species, histological and developmental data in A. muricatus suggest the existence of an underlying genetic influence on sex determination, consistent with an intermediate GSD-TSD system similar to that observed in P. vitticeps [Whiteley et al, 2021]. Efforts to characterize sex-linked loci in A. muricatus could provide new avenues for studying the higher sensitivity of sex reversals in the future.…”

Section: Reptilesmentioning

confidence: 67%

Do the Offspring of Sex Reversals Have Higher Sensitivity to Environmental Perturbations?

Piferrer¹,

Anastasiadi²

2021

Sex Dev

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Sex determination systems in vertebrates vary along a continuum from genetic (GSD) to environmental sex determination (ESD). Individuals that show a sexual phenotype opposite to their genotypic sex are called sex reversals. Aside from genetic elements, temperature, sex steroids, and exogenous chemicals are common factors triggering sex reversal, a phenomenon that may occur even in strict GSD species. In this paper, we review the literature on instances of sex reversal in fish, amphibians, reptiles, birds, and mammals. We focus on the offspring of sex-reversed parents in the instances that they can be produced, and show that in all cases studied the offspring of these sex-reversed parents exhibit a higher sensitivity to environmental perturbations than the offspring of non-sex-reversed parents. We suggest that the inheritance of this sensitivity, aside from possible genetic factors, is likely to be mediated by epigenetic mechanisms such as DNA methylation, since these mechanisms are responsive to environmental cues, and epigenetic modifications can be transmitted to the subsequent generations. Species with a chromosomal GSD system with environmental sensitivity and availability of genetic sex markers should be employed to further test whether offspring of sex-reversed parents have greater sensitivity to environmental perturbations. Future studies could also benefit from detailed whole-genome data in order to elucidate the underlying molecular mechanisms. Finally, we discuss the consequences of such higher sensitivity in the context of global climate change.

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Section: Reptilesmentioning

confidence: 67%

Do the Offspring of Sex Reversals Have Higher Sensitivity to Environmental Perturbations?

Piferrer¹,

Anastasiadi²

2021

Sex Dev

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“…Studies of the underlying mechanisms of TSD require a genome assembly and knowledge of genome organisation to identify genes on the sex chromosomes of species with genotypic sex determination (GSD) and their chromosomal and gene homology in closely related TSD species. This is particularly so in species with TSD that show evidence of cryptic residual or de novo genotypic influence on offspring sex ratios, as is suspected for A. muricatus (Whiteley et al, 2021).…”

Section: Introductionmentioning

confidence: 94%

Draft genomes of a male and female Australian jacky dragon (Amphibolurus muricatus)

Tian

Guo

Yang

et al. 2021

Preprint

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Australia is remarkable for its lizard diversity, with very high endemicity because of continental-scale diversification and adaptive radiation. We employed 10X Genomics Chromium linked-reads technology to generate male and female draft genomes of the jacky dragon (Amphibolurus muricatus), an Australian dragon lizard (family Agamidae). The assemblies are 1.8 Gb in size and have a repeat content (38%) and GC content (42%) similar to other dragon lizards. The contig N50 values for the assemblies were 37.2 kb (female) and 28.8 kb (male), with corresponding scaffold N50 values of 720.5 kb and 369 kb. The longest scaffold was 6.5 Mb in each assembly. The BUSCO completeness percentages were 92.2% and 90.8% respectively. These statistics are comparable to other lizard genomes assembled using similar technology. Phylogenetic comparisons show that Australian dragon lizard species split from a common ancestor around 33.4 million years ago. The draft A. muricatus assemblies will be a valuable resource for understanding lizard sex determination and the evolution and conservation of Australian dragon lizards.

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“…Modelling has led to the hypothesis that species with this pattern may possess an underlying ZZ/ZW system [Quinn et al, 2011]. Indeed, there is evidence to suggest this may be the case for the Jacky dragon, A. muricatus [Whiteley et al, 2021a].…”

Section: Detection Of Sex Reversalmentioning

confidence: 99%

Temperature-Induced Sex Reversal in Reptiles: Prevalence, Discovery, and Evolutionary Implications

Whiteley

Castelli

Dissanayake

et al. 2021

Sex Dev

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Sex reversal is the process by which an individual develops a phenotypic sex that is discordant with its chromosomal or genotypic sex. It occurs in many lineages of ectothermic vertebrates, such as fish, amphibians, and at least one agamid and one scincid reptile species. Sex reversal is usually triggered by an environmental cue that alters the genetically determined process of sexual differentiation, but it can also be caused by exposure to exogenous chemicals, hormones, or pollutants. Despite the occurrence of both temperature-dependent sex determination (TSD) and genetic sex determination (GSD) broadly among reptiles, only 2 species of squamates have thus far been demonstrated to possess sex reversal in nature (GSD with overriding thermal influence). The lack of species with unambiguously identified sex reversal is not necessarily a reflection of a low incidence of this trait among reptiles. Indeed, sex reversal may be relatively common in reptiles, but little is known of its prevalence, the mechanisms by which it occurs, or the consequences of sex reversal for species in the wild under a changing climate. In this review, we present a roadmap to the discovery of sex reversal in reptiles, outlining the various techniques that allow new occurrences of sex reversal to be identified, the molecular mechanisms that may be involved in sex reversal and how to identify them, and approaches for assessing the impacts of sex reversal in wild populations. We discuss the evolutionary implications of sex reversal and use the central bearded dragon (<i>Pogona vitticeps</i>) and the eastern three-lined skink (<i>Bassiana duperreyi</i>) as examples of how species with opposing patterns of sex reversal may be impacted differently by our rapidly changing climate. Ultimately, this review serves to highlight the importance of understanding sex reversal both in the laboratory and in wild populations and proposes practical solutions to foster future research.

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Ovotestes suggest cryptic genetic influence in a reptile model for temperature-dependent sex determination

Cited by 14 publications

References 58 publications

Do the Offspring of Sex Reversals Have Higher Sensitivity to Environmental Perturbations?

Do the Offspring of Sex Reversals Have Higher Sensitivity to Environmental Perturbations?

Draft genomes of a male and female Australian jacky dragon (Amphibolurus muricatus)

Temperature-Induced Sex Reversal in Reptiles: Prevalence, Discovery, and Evolutionary Implications

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