An orchid (Oncidium Gower Ramsey) AP3-like MADS gene regulates floral formation and initiation.
cDNA for a B group MADS box gene OMADS3 was isolated and characterized from Oncidium Gower Ramsey, an important species of orchid. OMADS3 encoding a 204 amino acid protein showed high sequence homology to both paleoAP3 and TM6 lineage of B group MADS box gene such as monocots AP3 homologue LMADS1 in lily and GDEF1 in Gerbera hybrida. Despite the sequence homology, consensus motifs identified in the C-terminal region of B group genes were absent in OMADS3. Southern analysis indicated that OMADS3 was present in O. Gower Ramsey genome in low copy numbers. Different from most B group genes, OMADS3 mRNA was detected in all four floral organs as well as in vegetative leaves. This is similar to the expression pattern of GDEF1. 35S::OMADS3 transgenic plants showed novel phenotypes by producing terminal flowers similar to those observed in transgenic plants ectopically expressed A functional genes such as AP1. Ectopic expression of OMADS3 cDNA truncated with the MADS box or C terminal region in Arabidopsis generated novel ap2-like flowers in which sepals and petals were converted into carpel-like and stamen-like structures. Yeast two-hybrid analysis indicated that OMADS3 is able to strongly form homodimers. Our results suggested that OMADS3 might represent an ancestral form of TM6-like gene which was conserved in monocots with a function similar to A functional gene in regulating flower formation as well as floral initiation.
Hsu
Hsing-Fun
HF
Graduate Institute of Agricultural Biotechnology, National Chung Hsing University, Taichung, Taiwan, 40227 ROC.
Yang
Chang-Hsien
CH
D000595:Amino Acid Sequence; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D018076:DNA, Complementary / Q000737:chemistry / Q000235:genetics; D035264:Flowers / Q000235:genetics / Q000254:growth & development*; D018506:Gene Expression Regulation, Plant; D018398:Homeodomain Proteins / Q000235:genetics / Q000378:metabolism; D026161:MADS Domain Proteins / Q000235:genetics / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D029595:Orchidaceae / Q000235:genetics*; D010802:Phylogeny; D010940:Plant Proteins; D030821:Plants, Genetically Modified; D012441:Saccharomyces cerevisiae / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism; D020798:Two-Hybrid System Techniques
C101342:APETALA 3 protein, Arabidopsis; C499534:APETALA2 protein, Arabidopsis; D029681:Arabidopsis Proteins; D018076:DNA, Complementary; D018398:Homeodomain Proteins; D026161:MADS Domain Proteins; D009687:Nuclear Proteins; D010940:Plant Proteins; D014157:Transcription Factors