Resolving the molecular genetics of monoecy and dioecy in the Salicaceae family to explore the evolution of plant sexual systems

• Applicant: Dr. Niels Müller
• Subject Area: Plant Genetics and Genomics
• Term: since 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 544948635

While our understanding of the genetic basis of dioecy in specific plant species and genera is rapidly expanding, there is still a substantial lack of knowledge regarding the molecular evolution of sex-determining genes over longer evolutionary timescales and during transitions between sexual systems. Are the sex-determining genes conserved across distant genera? Can the same genetic networks control sex determination in different sexual systems, such as monoecy and dioecy? By studying the molecular genetics of sex determination in several related dioecious and monoecious genera, these questions can finally be addressed. Here, we propose to contribute to this effort by using the Salicaceae family as a model system, which comprises the well-studied dioecious systems poplar and willow where the ARR17 gene was repeatedly identified as a master regulator of sex determination. First, we want to work out the genetic and molecular basis of monoecy in Poliothyrsis sinensis, the closest monoecious relative of poplar and willow. To this end, we will perform an RNA-seq time-course experiment with female and male parts of the developing inflorescence. Second, we want to resolve the genetic basis of sex determination in the related dioecious genus Idesia. We will sequence female and male Idesia polycarpa individuals to identify the sex-determining region and characterize possible sex-determining genes. Third, we propose to test whether the ARR17 gene from different Salicaceae species can act as a sex switch in poplar. To this end, we will transform early-flowering male white poplar (Populus alba), which does not carry any ARR17 sequences, with increasingly divergent ARR17 genes. Finally, we want to artificially engineer monoecy in poplar by cis-regulatory manipulation and generation of an ARR17 expression gradient. In conclusion, the proposed project will use the Salicaceae family as a model system to provide new insights into the evolution of sex-determining genes and transitions between monoecy and dioecy. The results will contribute to our general understanding of the molecular evolution of plant sexual systems.

• DFG Programme: Research Grants
• International Connection: Canada
• Cooperation Partner: Professor Dr. Quentin Cronk