How petals change their spots: cis-regulatory re-wiring in Clarkia (Onagraceae).
A long-standing question in evolutionary developmental biology is how new traits evolve. Although most floral pigmentation studies have focused on how pigment intensity and composition diversify, few, if any, have explored how a pattern element can shift position. In the present study, we examine the genetic changes underlying shifts in the position of petal spots in Clarkia. Comparative transcriptome analyses were used to identify potential candidate genes responsible for spot formation. Co-segregation analyses in F2individuals segregating for different spot positions, quantitative PCR, and pyrosequencing, were used to confirm the role of the candidate gene in determining spot position. Transient expression assays were used to identify the expression domain of different alleles. An R2R3Myb transcription factor (CgMyb1) activated spot formation, and different alleles of CgMyb1 were expressed in different domains, leading to spot formation in different petal locations. Reporter assays revealed that promoters from different alleles determine different locations of expression. The evolutionary shift in spot position is due to one or more cis-regulatory changes in the promoter of CgMyb1, indicating that shifts in pattern element position can be caused by changes in a single gene, and that cis-regulatory rewiring can be used to alter the relative position of an existing character.
Department of Biology, Duke University, Durham, NC, 27708, USA.|Department of Agriculture, Nutrition and Veterinary Sciences, University of Nevada, Reno, NV, 89557, USA.
Talline R
TR
Martins
Department of Biology, Duke University, Durham, NC, 27708, USA.
Peng
P
Jiang
Department of Biology, Duke University, Durham, NC, 27708, USA.
Mark D
MD
Rausher
D000483:Alleles; D005075:Biological Evolution; D020090:Chromosome Segregation / Q000235:genetics; D031663:Clarkia / Q000033:anatomy & histology* / Q000235:genetics*; D035264:Flowers / Q000033:anatomy & histology* / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D008156:Luciferases / Q000378:metabolism; D010802:Phylogeny; D010940:Plant Proteins / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012045:Regulatory Sequences, Nucleic Acid / Q000235:genetics*; D013045:Species Specificity; D014157:Transcription Factors / Q000378:metabolism
D010940:Plant Proteins; D014157:Transcription Factors; D008156:Luciferases

Clarkia
; R2R3 Myb transcription factor; evo-devo; petal spots; pigmentation patterns; regulatory rewiring