CaMADS1, an AGAMOUS homologue from hazelnut, produces floral homeotic conversion when expressed in Arabidopsis

CaMADS1 is a floral-specific MADS box gene of hazelnut (Corylus avellana) w hich, according to its sequence and expression pattern, belongs to the AGAM OUS gene sub-family. To investigate whether CaMADS1 plays a role in specify ing stamen and carpel identity, this gene was ectopically expressed in Arab idopsis. The constitutive expression of CaMAADS1 in transgenic plants produ ced the homeotic conversion of first and second whorl organs: the first who rl exhibited carpelloid sepals and the second whorl showed staminoid featur es. This was expected on the basis of the ABC model, according to which ect opic expression of a functional AGAMOUS (a gene of class C) orthologue woul d suppress the A class homeotic function in the first and second whorls, le ading to transformation of these whorls into carpels and stamen, respective ly. These results indicate a functional equivalency between AGAMOUS and CaM ADS1, for which CaMADS1 might behave like a class C homeotic gene, controll ing the determination of stamen and carpel identity in hazelnut.