title: Transcriptomes of Plant Gametophytes Have a Higher Proportion of Rapidly Evolving and Young Genes than Sporophytes.
abstract: Reproductive traits in plants tend to evolve rapidly due to various causes that include plant-pollinator coevolution and pollen competition, but the genomic basis of reproductive trait evolution is still largely unknown. To characterize evolutionary patterns of genome wide gene expression in reproductive tissues in the gametophyte and to compare them to developmental stages of the sporophyte, we analyzed evolutionary conservation and genetic diversity of protein-coding genes using microarray-based transcriptome data from three plant species, Arabidopsis thaliana, rice (Oryza sativa), and soybean (Glycine max). In all three species a significant shift in gene expression occurs during gametogenesis in which genes of younger evolutionary age and higher genetic diversity contribute significantly more to the transcriptome than in other stages. We refer to this phenomenon as "evolutionary bulge" during plant reproductive development because it differentiates the gametophyte from the sporophyte. We show that multiple, not mutually exclusive, causes may explain the bulge pattern, most prominently reduced tissue complexity of the gametophyte, a varying extent of selection on reproductive traits during gametogenesis as well as differences between male and female tissues. This highlights the importance of plant reproduction for understanding evolutionary forces determining the relationship of genomic and phenotypic variation in plants.
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom toni.gossmann@gmail.com karl.schmid@uni-hohenheim.de.
authors.forename: Toni I
authors.initials: TI
authors.lastname: Gossmann
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany.
authors.forename: Dounia
authors.initials: D
authors.lastname: Saleh
authors.affiliation: Institute for Plant Biology and Zurich-Basel Plant Science Center, University of Zurich, Zurich, Switzerland.
authors.forename: Marc W
authors.initials: MW
authors.lastname: Schmid
authors.affiliation: Department of Animal and Plant Sciences, University of Sheffield, Sheffield, United Kingdom.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Spence
authors.affiliation: Institute of Plant Breeding, Seed Science and Population Genetics, University of Hohenheim, Stuttgart, Germany toni.gossmann@gmail.com karl.schmid@uni-hohenheim.de.
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Schmid
mesh_terms: D017360:Arabidopsis / Q000235:genetics; D005075:Biological Evolution; D019143:Evolution, Molecular; D020869:Gene Expression Profiling / Q000379:methods*; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant; D014644:Genetic Variation; D018745:Genome, Plant; D055993:Germ Cells, Plant; D012275:Oryza / Q000235:genetics; D063245:Plant Development / Q000235:genetics; D010940:Plant Proteins / Q000235:genetics; D010944:Plants / Q000235:genetics*; D013025:Glycine max / Q000235:genetics; D059467:Transcriptome
chemical_list: D010940:Plant Proteins
keywords: gametophyte.; plant evolution; reproduction; selection; transcriptome