Biology subjects

Shams, F.

Publications and source records attributed to Shams, F..

3 recordsLinked to original sources

bioRxiv2022

Sex-linked markers in an Australian frog Platyplectrum ornatum with a small genome and homomorphic sex chromosomes

Amphibians have highly diverse sex-determining modes leading to a notable interest in vertebrate sex determination and sex chromosome evolution. The identification of sex-determining systems in amphibians, however, is often difficult as a vast majority consist of homomorphic sex chromosomes making them hard to distinguish. In this study, we used Diversity Array Technology sequencing (DArTseq) to identify the sex-determining system in the ornate burrowing frog from Australia, Platyplectrum ornatum. We applied DArTseq to 44 individuals, 19 males and 25 females, collected from two locations to develop sex-linked markers. Unexpectedly, these 44 individuals were classified into two distinct population clusters based on our SNP analyses, 36 individuals in cluster-1, and 8 individuals in cluster-2. We then performed sex-linkage analyses separately in each cluster. We identified 35 sex-linked markers from cluster-1, which were all associated with maleness. Therefore, P. ornatum cluster-1 is utilising a male heterogametic (XX/XY) sex-determining system. On the other hand, we identified 210 sex-linked markers from cluster-2, of which 89 were male specific, i.e., identifying XX/XY sex determining system and 111 were female specific, i.e., identifying ZZ/ZW sex determining system, suggesting existence of either male or female heterogametic sex determining system in cluster-2. We also performed cytogenetic analyses in 1 male and 1 female from cluster-1; however, we did not detect any visible differentiation between the X and Y sex chromosomes. We also mapped sex-linked markers from the two clusters against the P. ornatum genome and our comparative analysis indicated that the sex chromosomes in both clusters shared homologies to chromosome 10 (autosome) of Rana temporaria and ZWY sex chromosome of Xenopus tropicalis. It is plausible that the cluster-2 has a potential to be either male or female heterogamety in sex determination, requiring further investigation.

genomics↗

bioRxiv2022

Contrasting reproductive strategies despite convergent traits for two dryland river-floodplain species

Aquatic plants share a range of convergent reproductive strategies, such as the ability to reproduce both sexually and asexually through vegetative growth. In dryland river systems, floodplain inundation is infrequent and irregular, and wetlands consist of discrete and unstable habitat patches. In these systems life-history strategies such as long-distance dispersal, seed longevity, self-fertilisation, and reproduction from vegetative propagules are important strategies which allow plants to persist. Using two aquatic plants Marsilea drummondii and Eleocharis acuta, we investigated the proportions of sexual and asexual reproduction and self-fertilisation employing next generation sequencing approaches and used this information to understand population genetic structure in a large inland floodplain, in western New South Wales (NSW) Australia. Asexual vegetative reproduction and self-fertilisation was more common in M. drummondii, but both species used sexual reproduction as the main mode of reproduction. This resulted in highly differentiated genetic structure between wetlands and similar genetic structure within wetlands. The similarity in genetic structure was influenced by the wetland in the two species highlighting the influence of the floodplain landscape and hydrology in structuring population genetic structure. The high levels of genetic variation among wetlands and low variation within wetlands suggests that dispersal and pollination occur within close proximity and that gene flow is restricted. This suggests a reliance on locally sourced (persistent) seed, rather than asexual (clonal) reproduction or recolonisation via dispersal, for population maintenance in plants in dryland rivers. This highlights the importance of floodplain inundation to promote seed germination, establishment and reproduction in dryland regions.

plant biology↗

bioRxiv2021

Diversity of reptile sex chromosome evolution revealed by cytogenetic and linked-read sequencing

Reptile sex determination is attracting much attention because the great diversity of sex-determination and dosage compensation mechanisms permits us to approach fundamental questions about sex chromosome turnover and evolution. However, reptile sex chromosome variation remains largely uncharacterized and no reptile master sex determination genes have yet been identified. Here we describe a powerful and cost-effective "chromosomics" approach, combining probes generated from the microdissected sex chromosomes with transcriptome sequencing to explore this diversity in non-model Australian reptiles with heteromorphic or cryptic sex chromosomes. We tested the pipeline on a turtle, a gecko, and a worm-lizard, and we also identified sequences located on sex chromosomes in a monitor lizard using linked-read sequencing. Genes identified on sex chromosomes were compared to the chicken genome to identify homologous regions among the four species. We identified candidate sex determining genes within these regions, including conserved vertebrate sex-determining genes pdgfa, pdgfra amh and wt1, and demonstrated their testis or ovary-specific expression. All four species showed gene-by-gene rather than chromosome-wide dosage compensation. Our results imply that reptile sex chromosomes originated by independent acquisition of sex-determining genes on different autosomes, as well as translocations between different ancestral macro- and micro-chromosomes. We discuss the evolutionary drivers of the slow differentiation, but rapid turnover, of reptile sex chromosomes.

genomics↗