Y-linked iDmrt1 paralogue (iDMY) in the Eastern spiny lobster， Sagmariasus verreauxi: The first invertebrate sex-linked Dmrt.

Sex determination pathways are extensively diverse across species， with the master sex-determinants being the most variable element. Despite this， there is a family of DM-domain transcription factors (Dmrts)， which hold a highly conserved function in sexual development. This work is the first to describe a heterogametic sex-linked Dmrt in an invertebrate species， the Eastern spiny lobster， Sagmariasus verreauxi. We have termed the Y-linked， truncated paralogue of the autosomal iDmrt1， Sv-iDMY. Considering the master sex-determining function of both DMY in medaka and DM-W in frog， we hypothesised a similar function of Sv-iDMY. By conducting temporal expression analyses during embryogenesis we have identified a putative male sex-determining period during which iDMY>iDmrt1. Employing a GAL4-transactivation assay we then demonstrate the dominant negative suppression of iDMY over its autosomal iDmrt1 paralogue， suggesting the mechanism with which iDMY determines sex. Comparative analyses of Sv-iDMY， DM-W and medaka DMY， highlight the C'-mediated features of oligomerisation and transactivation as central to the mechanism that each exerts. Indeed， these features may underpin the plasticity facilitating the convergent emergence of these three sporadic sex-linked master-Dmrts.