title: Organ boundary NAC-domain transcription factors are implicated in the evolution of petal fusion.
abstract: Research rationale: Evolution of fused petals (sympetaly) is considered to be an important innovation that has repeatedly led to increased pollination efficiency, resulting in accelerated rates of plant diversification. Although little is known about the underlying regulation of sympetaly, genetic pathways ancestrally involved in organ boundary establishment (e.g. CUP SHAPED COTYLEDON [CUC] 1-3 genes) are strong candidates. In sympetalous petunia, mutations in the CUC1/2-like orthologue NO APICAL MERISTEM (NAM) inhibit shoot apical meristem formation. Despite this, occasional 'escape shoots' develop flowers with extra petals and fused inter-floral whorl organs. Central methods: To To determine if petunia CUC-like genes regulate additional floral patterning, we used virus-induced silencing (VIGS) following establishment of healthy shoot apices to re-examine the role of NAM in petunia petal development, and uniquely characterise the CUC3 orthologue NH16.
  
  
  RESULTS
  Confirming previous results, we found that reduced floral NAM/NH16 expression caused increased petal-stamen and stamen-carpel fusion, and often produced extra petals. However, further to previous results, all VIGS plants infected with NAM or NH16 constructs exhibited reduced fusion in the petal whorl compared to control plants.
  
  
  CONCLUSIONS
  Together with previous data, our results demonstrate conservation of petunia CUC-like genes in establishing inter-floral whorl organ boundaries, as well as functional evolution to affect the fusion of petunia petals.
authors: Department of Plant Biology, The University of Vermont, Burlington, VT, USA.
authors: J
authors: J
authors: Zhong
authors: Department of Plant Biology, The University of Vermont, Burlington, VT, USA.
authors: S
authors: S
authors: Powell
authors: Department of Plant Biology, The University of Vermont, Burlington, VT, USA. Jill.Preston@uvm.edu.
authors: J C
authors: JC
authors: Preston
mesh_terms: D005075:Biological Evolution; D018548:Cotyledon / Q000033:anatomy & histology / Q000235:genetics; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics*; D020868:Gene Silencing; D009154:Mutation; D032306:Petunia / Q000033:anatomy & histology / Q000235:genetics*; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000235:genetics* / Q000378:metabolism; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C099172:NAM protein, Petunia hybrida; D010940:Plant Proteins; D014157:Transcription Factors
keywords: 
  
  NO APICAL MERISTEM
  
  ; 
  CUP-SHAPED COTYLEDON
  ; flower diversification; organ fusion; petunia; sympetaly