title: Cross species selection scans identify components of C4 photosynthesis in the grasses.
abstract: C4photosynthesis is perhaps one of the best examples of convergent adaptive evolution with over 25 independent origins in the grasses (Poaceae) alone. The availability of high quality grass genome sequences presents new opportunities to explore the mechanisms underlying this complex trait using evolutionary biology-based approaches. In this study, we performed genome-wide cross-species selection scans in C4lineages to facilitate discovery of C4genes. The study was enabled by the well conserved collinearity of grass genomes and the recently sequenced genome of a C3panicoid grass, Dichanthelium oligosanthes This method, in contrast to previous studies, does not rely on any a priori knowledge of the genes that contribute to biochemical or anatomical innovations associated with C4photosynthesis. We identified a list of 88 candidate genes that include both known and potentially novel components of the C4pathway. This set includes the carbon shuttle enzymes pyruvate, phosphate dikinase, phosphoenolpyruvate carboxylase and NADP malic enzyme as well as several predicted transporter proteins that likely play an essential role in promoting the flux of metabolites between the bundle sheath and mesophyll cells. Importantly, this approach demonstrates the application of fundamental molecular evolution principles to dissect the genetic basis of a complex photosynthetic adaptation in plants. Furthermore, we demonstrate how the output of the selection scans can be combined with expression data to provide additional power to prioritize candidate gene lists and suggest novel opportunities for pathway engineering.
authors.affiliation: Donald Danforth Plant Science Center, 975 N Warson Rd, St Louis, MO 63132, USA.
authors.forename: Pu
authors.identifier: 0000-0003-1133-2716
authors.initials: P
authors.lastname: Huang
authors.affiliation: Department of Crop Sciences, University of Illinois Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Studer
authors.affiliation: Department of Agronomy and Horticulture, University of Nebraska-Lincoln, Lincoln, NE 68588, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Schnable
authors.affiliation: Donald Danforth Plant Science Center, 975 N Warson Rd, St Louis, MO 63132, USA.
authors.forename: Elizabeth A
authors.initials: EA
authors.lastname: Kellogg
authors.affiliation: Donald Danforth Plant Science Center, 975 N Warson Rd, St Louis, MO 63132, USA tbrutnell@danforthcenter.org.
authors.forename: Thomas P
authors.initials: TP
authors.lastname: Brutnell
mesh_terms: D000220:Adaptation, Biological; D019143:Evolution, Molecular; D018745:Genome, Plant; D055106:Genome-Wide Association Study; D010788:Photosynthesis / Q000235:genetics*; D006109:Poaceae / Q000235:genetics*; D012641:Selection, Genetic
keywords: Adaptation; C4 photosynthesis; cross-species selection scans; gene discovery; grasses; parallel evolution.