Genomics of sex determination in the conifer species Taxus baccata L.

• Applicant: Privatdozentin Dr. Birgit Kersten
• Subject Area: Plant Genetics and Genomics
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 497528752

The exceptionally large and complex genomes of dioecious gymnosperms make the elucidation of the genetic basis of sex determination much more challenging than in angiosperms, where our related understanding is rapidly expanding. In the angiosperm genus Populus, we have identified sex-determining regions (SDRs) in different species and elucidated that a single gene, the type-A response regulator ARR17 serves as master regulator (switch) for sex determination, based on long-read sequencing and resequencing strategies. These findings supported one-factor models for the evolution of dioecy - as an alternative to the classical two-factor model – as well as the hypothesis that genes controlling sex expression in monoecious species may often also be involved in sex determination in related dioecious species (Renner and Müller, 2021). Plant genera with monecious and dioecious member species, such as the gymnosperm genus Taxus, represent perfect models to further explore this hypothesis by elucidating the genetic and molecular basis for sex determination in related species. In collaboration with the DRESDEN-concept Genome Center, we will perform long-read sequencing and chromosome-level de novo assembly of a male and a female Taxus baccata reference genome as well as apply re-sequencing and RNA-seq approaches to identify the heterogametic sex, characterize the sex chromosomes, localize the SDR and identify (potential) sex-determining genes/factors. This will provide a basis to address the question if one or two genes will be responsible for sex determination in this dioecious species, and if a type-A response regulator may be involved. A synthesis of all known (candidate) genes for sex determination in dioecious plant species in the current DFG project pointed to a potential involvement of such genes also in species outside the Salicaceae family, including the gymnosperm Ginkgo biloba (Leite Montalvao et al. 2021). Comparative genomics with available reference genomes of other Taxus species will provide initial clues as to whether there is possibly the same sex-determining gene (re)used or whether novel genetic mechanisms evolved. Moreover, based on sex-linked genetic differences identified in the SDR of Taxus baccata, molecular markers for genetic sex determination will be developed, which are of great practical importance in a species reaching sexual maturity at an age above 15 years.

• DFG Programme: Research Grants