Résumé
MADS box genes encode a highly conserved family of transcription factors of which many are involved in the control of flowering. MADS box genes may act at a number of different developmental stages, from the initiation of the inflorescence meristem to the determination of floral architecture. We are studying the diversity, expression patterns and functional activities of MADS box genes cloned from oil palm, a species which produces male and female flowers alternately on the same plant. A number of aspects of oil palm flowering are of particular interest, including the determination of an epigenetic floral abnormality induced by tissue culture and its relationship to natural genetic mutants of similar phenotype. In order to identify genes which participate in the regulation of oil palm flowering, a characterisation of the MADS box family was undertaken. Eleven different MADS box cDNA clones were isolated by screening oil palm inflorescence cDNA libraries, using homologous probes previously obtained by PCR. The polypeptides encoded by the oil palm cDNAs isolated show the typical molecular organisation of plant MADS box proteins, termed MIKC. Based on sequence comparison, the oil palm genes were found to belong to four distinct subclasses of the MADS box family, namely those represented in Arabidopsis thaliana by APETALA1 (AP1), PISTILLATA (PI), AGL6 and the SEPALLATA (SEP) genes. Transcript accumulation was investigated for several members of the family, revealing expression patterns which varied according to developmental stage, flower sex and phenotype. These data provide the first clues to the functions of the oil palm MADS box genes studied. (Texte intégral)