Organ identity genes and modified patterns of flower development in Gerbera hybrida (Asteraceae)

• Published in: The Plant journal : for cell and molecular biology 1999-01, Vol.17 (1), p.51-62
• Main Authors: Yu, Deyue, Kotilainen, Mika, Pöllänen, Eija, Mehto, Merja, Elomaa, Paula, Helariutta, Yrjö, Albert, Victor A., Teeri, Teemu H.
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Antirrhinum; Arabidopsis; Asteraceae; Asteraceae - genetics; Asteraceae - physiology; Asteraceae - ultrastructure; Base Sequence; Biological and medical sciences; Biology and morphogenesis of the reproductive apparatus. Photoperiodism, vernalisation; Cloning, Molecular; DNA Primers; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - genetics; Economic plant physiology; Flowering, floral biology, reproduction patterns; Fundamental and applied biological sciences. Psychology; Gene Expression Regulation, Plant; Genes, Homeobox; Gerbera hybrida; Growth and development; Homeodomain Proteins - genetics; MADS Domain Proteins; Microscopy, Electron, Scanning; Molecular Sequence Data; Phylogeny; Plant physiology and development; Plant Proteins; Plant Stems - ultrastructure; Plants, Genetically Modified; Polymerase Chain Reaction; Recombinant Proteins - biosynthesis; Transcription Factors - biosynthesis; Transcription Factors - genetics; Vegetative and sexual reproduction, floral biology, fructification
• ISSN: 0960-7412; 1365-313X
• DOI: 10.1046/j.1365-313X.1999.00351.x

Summary We have used Gerbera hybrida (the cultivated ornamental, gerbera) to investigate the molecular basis of flower development in Asteraceae, a family of flowering plants that have heteromorphic flowers and specialized floral organs. Flowers of the same genotype may differ in a number of parameters, including sex expression, symmetry, sympetaly and pigmentation. In order to study the role of organ identity determination in these phenomena we isolated and functionally analysed six MADS box genes from gerbera; these were shown by phylogenetic analysis to be orthologous to well characterized regulatory genes described from Arabidopsis and Antirrhinum . Expression analysis suggests that the two gerbera agamous orthologues, the globosa orthologue and one of the deficiens orthologues may have functional equivalency to their counterparts, participating in the C and B functions, respectively. However, the function of a second deficiens orthologue appears unrelated to the B function, and that of a squamosa orthologue seems distinct from squamosa as well as from the A function. The induction patterns of gerbera MADS box genes conform spatiotemporally to the multi‐flowered, head‐like inflorescence typical of Asteraceae. Furthermore, gerbera plants transgenic for the newly isolated MADS box genes shed light onto the mechanistic basis for some floral characteristics that are typical for Asteraceae. We can conclude, therefore, that the pappus bristles are sepals highly modified for seed dispersal, and that organ abortion in the female marginal flowers is dependent upon organ identity and not organ position when position is homeotically altered.