title: Analysis of the APETALA3- and PISTILLATA-like genes in Hedyosmum orientale (Chloranthaceae) provides insight into the evolution of the floral homeotic B-function in angiosperms.
abstract: OBJECTIVE
  According to the floral ABC model, B-function genes appear to play a key role in the origin and diversification of the perianth during the evolution of angiosperms. The basal angiosperm Hedyosmum orientale (Chloranthaceae) has unisexual inflorescences associated with a seemingly primitive reproductive morphology and a reduced perianth structure in female flowers. The aim of this study was to investigate the nature of the perianth and the evolutionary state of the B-function programme in this species.
  
  
  METHODS
  A series of experiments were conducted to characterize B-gene homologues isolated from H. orientale, including scanning electron microscopy to observe the development of floral organs, phylogenetic analysis to reconstruct gene evolutionary history, reverse transcription-PCR, quantitative real-time PCR and in situ hybridization to identify gene expression patterns, the yeast two-hybrid assay to explore protein dimerization affinities, and transgenic analyses in Arabidopsis thaliana to determine activities of the encoded proteins.
  
  
  RESULTS
  The expression of HoAP3 genes was restricted to stamens, whereas HoPI genes were broadly expressed in all floral organs. HoAP3 was able to partially restore the stamen but not petal identity in Arabidopsis ap3-3 mutants. In contrast, HoPI could rescue aspects of both stamen and petal development in Arabidopsis pi-1 mutants. When the complete C-terminal sequence of HoPI was deleted, however, no or weak transgenic phenotypes were observed and homodimerization capability was completely abolished.
  
  
  CONCLUSIONS
  The results suggest that Hedyosmum AP3-like genes have an ancestral function in specifying male reproductive organs, and that the activity of the encoded PI-like proteins is highly conserved between Hedyosmum and Arabidopsis. Moreover, there is evidence that the C-terminal region is important for the function of HoPI. Our findings indicate that the development of the proposed perianth in Hedyosmum does not rely on the B homeotic function.
authors: Key Laboratory of Plant Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 100093, China.
authors: Shujun
authors: S
authors: Liu
authors: Yonghua
authors: Y
authors: Sun
authors: Xiaoqiu
authors: X
authors: Du
authors: Qijiang
authors: Q
authors: Xu
authors: Feng
authors: F
authors: Wu
authors: Zheng
authors: Z
authors: Meng
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D019143:Evolution, Molecular; D035264:Flowers / Q000235:genetics* / Q000648:ultrastructure; D018506:Gene Expression Regulation, Plant; D005801:Genes, Homeobox / Q000235:genetics*; D017343:Genes, Plant / Q000235:genetics*; D017403:In Situ Hybridization; D019684:Magnoliopsida / Q000235:genetics* / Q000648:ultrastructure; D008969:Molecular Sequence Data; D010641:Phenotype; D010802:Phylogeny; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D030821:Plants, Genetically Modified; D011485:Protein Binding; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020539:Sequence Analysis, Protein; D020798:Two-Hybrid System Techniques
chemical_list: D010940:Plant Proteins; D012333:RNA, Messenger
keywords: APETALA3; C-terminal region; Chloranthaceae; Floral homeotic B function; Hedyosmum orientale; HoAP3; HoPI; PISTILLATA; homodimerization
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