Abstract
BackgroundThe inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae) consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum. Despite great interest in plant morphological evolution and the tractability of the gerbera system, very little is known regarding genetic mechanisms involved in flower type specification. Here, we provide comparative staging of ray and disc flower development and microarray screening for differentially expressed genes, accomplished via microdissection of hundreds of coordinately developing flower primordia.ResultsUsing a 9K gerbera cDNA microarray we identified a number of genes with putative specificity to individual flower types. Intrestingly, several of these encode homologs of MADS-box transcription factors otherwise known to regulate flower organ development. From these and previously obtained data, we hypothesize the functions and protein-protein interactions of several gerbera MADS-box factors.ConclusionOur RNA expression results suggest that flower-type specific MADS protein complexes may play a central role in differential development of ray and disc flowers across the gerbera capitulum, and that some commonality is shared with known protein functions in floral organ determination. These findings support the intriguing conjecture that the gerbera flowering head is more than a mere floral analog at the level of gene regulation.
Highlights
The inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae) consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum
Our RNA expression results suggest that flower-type specific MADS protein complexes may play a central role in differential development of ray and disc flowers across the gerbera capitulum, and that some commonality is shared with known protein functions in floral organ determination
Undifferentiated ray flower primordia are the first to arise in inflorescences of less than 6 mm in diameter, whereas the first disc flower primordia are detected in inflorescences of approximately 6–8 mm in diameter (Figure 1)
Summary
The inflorescence of the cut-flower crop Gerbera hybrida (Asteraceae) consists of two principal flower types, ray and disc, which form a tightly packed head, or capitulum. The inflorescences of Gerbera hybrida (Asteraceae) are composed of three different types of flowers (ray, trans, disc) that are tightly packed into a condensed, radially organized flower head (capitulum). The presence of morphologically different flower types within a single genotype makes gerbera a unique target for reproductive developmental studies, since the traditional eudicot model plants (Arabidopsis, Antirrhinum and Petunia) bear only single flower forms in their inflorescences. The first stages of development are morphologically similar in all flower types, with only the position of individual flower primordia in the developing capitulum conferring their developmental fate. Corolla size and color can vary continuosly in different gerbera varieties [2]
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