(800-125) Identifying candidate sex-determining genes and characterizing the non-recombining regions of the sex chromosomes of Morella cerifera & Morella rubra
PhD Student Auburn University & HudsonAlpha Institute for Biotechnology Huntsville, Alabama
Body of Abstract: The non-recombining regions of sex chromosomes are models for how selection drives reduced recombination in genomes and the emergence of sex-determining genes. They can illuminate how this phenomenon of selective suppression has emerged and is maintained in these and other genomic regions. Having evolved thousands of times in angiosperms, sex chromosomes are as diverse in their genomic composition as the dioecious species that contain them. High-quality reference genomes for dioecious species are critical to understanding the structure and content of sex-determining regions (SDRs), yet they are some of the most challenging to assemble and characterize due to the repetitiveness and variability of these regions. Morella cerifera and its relatives offer an excellent system for exploring SDR evolution across a clade due to their small genomes (~300 Mbp), diploidy, and the availability of monoecious mutants for comparative study. Here, we present a fully phased, chromosome-scale genome for M. cerifera, that showcases a 7.5 Mbp SDR in a ZZ/ZW system. The SDR is characterized by a dynamic array of structural variations, including two local translocations and 4 Mbp of insertions that are enriched in repetitive elements. Although putatively of the same origin, the M. cerifera SDR differs in size and gene content from Morella rubra, highlighting sequence diversity even within the same genus. We find two candidate sex-determining genes shared between the two SDRs: FLOWERING LOCUS T (FT) and entâcopalyl diphosphate synthase (CPS). We are currently sequencing additional male and female individuals from across the genus to characterize shifts of pseudoautosomal region (PAR) boundaries and evolution of strata in these regions. Further comparisons within entirely dioecious clades like the genus Morella may provide greater insights into sex chromosome turnover or conservation in these clades and what may contribute to the differential stability of these regions over time and across lineages.