Isolation of genes from female sterile flowers in Medicago sativa

A better knowledge of female sporogenesis and gametogenesis could have several practical applications, from commercial hybrid seed production to gene containment in GM crops. With the purpose of isolating genes involved in the megasporogenesis process, the cDNA-AFLP technique was employed to isolate transcript-derived fragments (TDF) differentially expressed between female-fertile and female-sterile full-sib alfalfa plants. This female sterility trait involves female-specific arrest of sporogenesis at early prophase associated with ectopic, massive callose deposition within the nucellus. Ninety-six TDFs were generated and BLAST analyses revealed similarities with genes involved in different Gene Ontology categories. Three TDFs were selected based on their putative functions: showing high similarity to a soybean flower-expressed beta 1,3-glucanase, to an Arabidopsis thaliana MAPKKK, and to an A. thaliana eukaryotic initiation translation factor eIF4G III, respectively. The full length mRNA sequences were obtained. RT-PCR and in situ hybridizations were performed to confirm differential expression during flower development. The genomic organization of the three genes was assessed through sequencing and Southern experiments. Sequence polymorphisms were found between sterile and fertile plants. Our approach based on differential display and bulked segregant analysis was successful in isolating genes that were differentially expressed between fertile and sterile alfalfa plants.