Functional characterization of MADS box genes involved in the determination of oil palm flower structure.

In order to study the molecular regulation of flower development in the monoecious species oil palm (Elaeis guineensis), cDNAs of 12 MADS box genes from this plant belonging to seven distinct subfamilies were previously isolated and characterized. Here studies carried out on five of these genes, each likely to be involved in floral morphogenesis: EgSQUA1 (SQUAMOSA subfamily); EgAGL2-1 (AGL2 subfamily); EgGLO2 (GLOBOSA subfamily); EgDEF1 (DEFICIENS subfamily); and EgAG2 (AGAMOUS subfamily), are described. In order to determine where and when in the plant these genes are likely to function, their spatial and temporal patterns of expression were studied during the development of male and female inflorescences, either of normal phenotype or displaying a homeotic flowering abnormality known as mantled. In parallel, the phenotypic effects of ectopically expressing these genes in transgenic Arabidopsis thaliana plants were analysed. The data suggest a broad conservation of floral homeotic gene functions between oil palm and previously described model species, although a few minor variations in the zones of activity of certain genes cannot be excluded. The data also indicate distinct molecular identities for the morphologically similar floral organs of whorls 1 and 2. They also reveal reduced expression of putative B, C/D, and E class genes in mantled flowers, which undergo a homeotic transformation comparable to B class mutants of model species.