Progress 10/01/03 to 09/30/04
Outputs
This report serves to document research conducted under a trust agreement between ARS and NRI. With funding from NRI, we proved we had cloned the branched silkless (bd1) gene in maize. The bd1 gene is required for the production of flowers in maize. In its absence, the ears are sterile. We showed that the bd1 gene is conserved in all grasses and is fundamental to the arrangement of floral organs in the grasses. We also showed that orthologs in rice and sorghum have the same expression pattern. The ortholog in rice is called frizzy panicle, which has a mutant phenotype very similar to that of bd. We have used rice to try and find genes that are differentially expressed. In a collaboration with Syngenta, we prepared RNA from fzp mutants and wild-type sibs and the RNA was hybridized to Affymetrix chips that contained probes from rice 40,000 genes. The average absolute values from two replicate rice experiments were calculated and analyzed. 102 genes are up-regulated in
wild-type sibs compared to fzp mutants, 38 of which are regulatory genes. Many of these genes are known floral meristem identity genes such as the rice orthologues of AGAMOUS and APETELA3, demonstrating the effectiveness of the experiment as floral meristem identity genes were enriched for in this experiment. Conversely, 133 genes are up regulated in fzp compared to wild type, 12 of which are regulatory in nature. Since the ERF domain of FZP is identical to BD1, the binding sequence for both proteins should be the same. Therefore, the promoters of all genes up or down in fzp were searched for the presence of the BD1 binding site. 26 out of 102 genes from the wild type compared to fzp pool contained the binding site, while 18 out of 133 genes from the converse experiment contained the BD1 binding site. We cloned new members of the ERF gene family that may be involved in development of the maize inflorescence by screening a 2 mm ear cDNA library using the full length BD1 cDNA as a
probe. Ears at this stage are producing SPM and SM and have not yet made floral organs. The screen yielded 15 clones coding for putative ERF transcription factors. Northern blot and RT-PCR analysis narrowed down the pool of clones to four, we call ERF 15A, 15B, 4A and 4B, all of which showed expression just in ear and tassel. In a collaboration with Pioneer Hy-Bred, we have insertional alleles for all of these genes and are introgressing the alleles into inbreds for eventual phenotypic analysis.
Impacts
The BD gene is conserved in all grasses. From analysis of rice and maize, it appears to be essential for seed development. Knowledge of how the gene functions has implications for yield in all cereal crops.
Publications
- No publications reported this period
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