title: Distinct double flower varieties in Camellia japonica exhibit both expansion and contraction of C-class gene expression.
abstract: BACKGROUND
  Double flower domestication is of great value in ornamental plants and presents an excellent system to study the mechanism of morphological alterations by human selection. The classic ABC model provides a genetic framework underlying the control of floral organ identity and organogenesis from which key regulators have been identified and evaluated in many plant species. Recent molecular studies have underscored the importance of C-class homeotic genes, whose functional attenuation contributed to the floral diversity in various species. Cultivated Camellia japonica L. possesses several types of double flowers, however the molecular mechanism underlying their floral morphological diversification remains unclear.
  
  
  RESULTS
  In this study, we cloned the C-class orthologous gene CjAG in C. japonica. We analyzed the expression patterns of CjAG in wild C. japonica, and performed ectopic expression in Arabidopsis. These results revealed that CjAG shared conserved C-class function that controls stamen and carpel development. Further we analyzed the expression pattern of CjAG in two different C. japonica double-flower varieties, 'Shibaxueshi' and 'Jinpanlizhi', and showed that expression of CjAG was highly contracted in 'Shibaxueshi' but expanded in inner petals of 'Jinpanlizhi'. Moreover, detailed expression analyses of B- and C-class genes have uncovered differential patterns of B-class genes in the inner organs of 'Jinpanlizhi'.
  
  
  CONCLUSIONS
  These results demonstrated that the contraction and expansion of CjAG expression were associated with the formation of different types of double flowers. Our studies have manifested two different trajectories of double flower domestication regarding the C-class gene expression in C. japonica.
authors.forename: Yingkun
authors.initials: Y
authors.lastname: Sun
authors.forename: Zhengqi
authors.initials: Z
authors.lastname: Fan
authors.forename: Xinlei
authors.initials: X
authors.lastname: Li
authors.forename: Zhongchi
authors.initials: Z
authors.lastname: Liu
authors.forename: Jiyuan
authors.initials: J
authors.lastname: Li
authors.forename: Hengfu
authors.initials: H
authors.lastname: Yin
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics / Q000254:growth & development; D001483:Base Sequence; D028244:Camellia / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D003001:Cloning, Molecular; D035264:Flowers / Q000033:anatomy & histology / Q000235:genetics* / Q000254:growth & development; D015870:Gene Expression; D005801:Genes, Homeobox / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D019076:Transgenes