MADS BOX GENES EXPRESSED IN DEVELOPING INFLORESCENCES OF RICE AND SORGHUM

With the aim of elucidating the complex genetic system controlling flo wer morphogenesis in cereals, we have characterized two lice and two s orghum MADS box genes isolated from cDNA libraries made from developin g inflorescences. The rice clones OsMADS24 and OsMADS45, which share h igh homology with the Arabidopsis AGL2 and AGL4 MADS box genes, are ex pressed in the floral meristem, in all the primordia, and in mature fl oral organs. Hi,oh expression levels have also been found in developin g kernels. The sorghum clone SbMADS1 is also homologous to AGL2 and AG L4: expression analysis and mapping data suggest that it is the orthol og of OsMAADS24. The pattern of expression of SbMADS2, the other sorgh um MADS box gene, suggests that it may play a role as a meristem ident ity gene, as does AP1 in Arabidopsis, to which it shows considerable h omology. The four genes have been mapped on a rice RFLP genetic map: t he results are discussed in terms of synteny among cereals.