Plant Molecular Biology 28: 935-941, 1995. © 1995 Kluwer Academic Publishers. Printed in Belgium. 935 Short communication Gerbera hybrida (Asteraceae) imposes regulation at several anatomical levels during inflorescence development on the gene for dihydroflavonol-4-reductase Yrj0 Helariutta, Mika Kotilainen, Paula Elomaa and Teemu H. Teeri Institute of Biotechology, P.O. Box 45, Karvaamokuja 3 A, FIN-O0014 University of Helsinki, Helsinki, Finland Received 18 October 1994; accepted in revised form 1 February 1995 Key words: anthocyanin, Compositae, corolla, dfr, flower development, gene expression Abstract In the ornamental cut flower plant Gerbera hybrida the spatial distribution of regulatory molecules characteristic of differentiation of the composite inflorescence is visualized as the various patterns of anthocyanin pigmentation of different varieties. In order to identify genes that the plant can regulate according to these anatomical patterns, we have analysed gene expression affecting two enzymatic steps, chalcone synthase (CH S) and dihydroflavonol-4-reductase (DFR), in five gerbera varieties with spatially restricted anthocyanin pigmentation patterns. The dfr expression profiles vary at the levels of floral organ, flower type and region within corolla during inflorescence development according to the anthocyanin pigmentation of the cultivars. In contrast, chs expression, although regulated in a tissue-specific manner during inflorescence development, varies only occasionally. The variation in the dfr expression profiles between the varieties reveals spatially specific gene regulation that senses the differentiation events characteristic of the composite inflorescence. The differentiation of floral organs is initiated by a combinatorial action of a set of regulatory genes that operate in the shoot apical meristem repro- grammed to a reproductive phase [27]. These genes determine organ identity and are called ho- meotic genes since mutations in them alter the identity of one organ to another. As is the basic structure of the flower (four whorls of sepals, petals, stamens and carpels), the homeotic genes are structurally conserved among flowering plants [7]. However, little is known about the genes that act downstream of these organ identity-determin- ing genes and the differentiation process itself shows strikingly less conservation. In the Aster- aceae, for example, several adaptations in flower development are observed [25]. Different flower types (rays and discs) are typically found in their composite inflorescence, and the floral organs, especially calyx and stamens, are highly special- ized [ 18]. The corolla differentiates into extended, The nucleotide sequence data reported will appear in the EMBL, GenBank and DDBJ Nucleotide Sequence Databases under the accession numbers Z17221 (gdfrl) and Z38096 (gchsl).