title: Expressed sequence tags (ESTs) and phylogenetic analysis of floral genes from a paleoherb species, Asarum caudigerum.
abstract: OBJECTIVE
  Asarum caudigerum (Aristolochiaceae) is an important species of paleoherb in relation to understanding the origin and evolution of angiosperm flowers, due to its basal position in the angiosperms. The aim of this study was to isolate floral-related genes from A. caudigerum, and to infer evolutionary relationships among florally expression-related genes, to further illustrate the origin and diversification of flowers in angiosperms.
  
  
  METHODS
  A subtracted floral cDNA library was constructed from floral buds using suppression subtractive hybridization (SSH). The cDNA of floral buds and leaves at the seedling stage were used as a tester and a driver, respectively. To further identify the function of putative MADS-box transcription factors, phylogenetic trees were reconstructed in order to infer evolutionary relationships within the MADS-box gene family.
  
  
  RESULTS
  In the forward-subtracted floral cDNA library, 1920 clones were randomly sequenced, from which 567 unique expressed sequence tags (ESTs) were obtained. Among them, 127 genes failed to show significant similarity to any published sequences in GenBank and thus are putatively novel genes.
  
  
  CONCLUSIONS
  Phylogenetic analysis indicated that a total of 29 MADS-box transcription factors were members of the APETALA3(AP3) subfamily, while nine others were putative MADS-box transcription factors that formed a cluster with MADS-box genes isolated from Amborella, the basal-most angiosperm, and those from the gymnosperms. This suggests that the origin of A. caudigerum is intermediate between the angiosperms and gymnosperms.
authors: Laboratory of Biodiversity and Plant Biogeography, Kunming Institute of Botany, Chinese Academy of Sciences, Kunming 650204, China.
authors: Yinhe
authors: Y
authors: Zhao
authors: Guoying
authors: G
authors: Wang
authors: Jinpeng
authors: J
authors: Zhang
authors: Junbo
authors: J
authors: Yang
authors: Shang
authors: S
authors: Peng
authors: Lianming
authors: L
authors: Gao
authors: Chengyun
authors: C
authors: Li
authors: Jinyong
authors: J
authors: Hu
authors: Dezhu
authors: D
authors: Li
authors: Lizhi
authors: L
authors: Gao