Huylmans, A. K. | bioRxiv Science

bioRxiv2024

Recurrent sex chromosome turn-over in termites

Termites, together with cockroaches, belong to the Blattodea. They possess an XX/XY sex determination system which has evolved from an XX/X0 system present in other Blattodean species such as cockroaches and wood roaches. Little is currently known about the sex chromosomes of termites, their gene content, or their evolution. We here investigate the X chromosome of multiple termite species and compare them to the X chromosome of cockroaches using genomic and transcriptomic data. We find that the X chromosome of the termite Macrotermes natalensis is large and differentiated showing hall marks of sex chromosome evolution such as dosage compensation, while this does not seem to be the case in the other two termite species investigated here where sex chromosomes are probably evolutionary young. Furthermore, that X chromosome in M. natalensis is different from the X chromosome found in the cockroach Blattella germanica indicating at least one, potentially multiple, sex chromosome turn-over events during termite evolution.

evolutionary biology↗

bioRxiv2022

ZW sex-chromosome evolution and contagious parthenogenesis in Artemia brine shrimp

Eurasian brine shrimp (genus Artemia) have closely related sexual and asexual lineages of parthenogenetic females, which produce rare males at low frequencies. Although they are known to have ZW chromosomes, these are not well characterized, and it is unclear whether they are shared across the clade. Furthermore, the underlying genetic architecture of the transmission of asexuality, which can occur when rare males mate with closely related sexual females, is not well understood. We produced a chromosome-level assembly for the Eurasian species A. sinica and characterized in detail the pair of sex chromosomes of this species. We combined this with short-read genomic data for the sexual species A. sp. Kazakhstan and several lineages of A. parthenogenetica, allowing us to perform a first in-depth characterization of sex-chromosome evolution across the genus. We identified a small differentiated region of the ZW pair that is shared by all sexual and asexual lineages, supporting the shared ancestry of the sex chromosomes. We also inferred that recombination suppression has spread to larger sections of the chromosome independently in the American and Eurasian lineages. Finally, we took advantage of a rare male, which we backcrossed to sexual females, to explore the genetic basis of asexuality. Our results suggest that parthenogenesis may be partly controlled by a locus on the Z chromosome, highlighting the interplay between sex determination and asexuality.

evolutionary biology↗