Investigating the Role of the RAMOSA3 Gene in Brachypodium distachyon



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Understanding the genes that regulate floral organs in the Poaceae, the grass family, could increase grain production, contributing to food security. Species in Poaceae have diverse floral morphologies. Floral organ suppression contributes to this diversity. Zea mays (maize) has unisexual, staminate flowers containing pollen grains and unisexual pistillate flowers containing ovules. RAMOSA3 (RA3) and GRASSY TILLERS1 (GT1) are two genes that regulate carpel suppression to create staminate flowers. ra3 mutants have partially enlarged carpels and increased axillary branching. gt1;ra3 double mutants also have enhanced branching and enlarged pistils with silks emerging from the tassel. Enhanced branching suggests that RA3 regulates axillary meristem suppression in addition to carpel development. Another grass model system, Brachypodium distachyon (brachypodium), has bisexual flowers with stamens and pistils. Brachypodium and maize have orthologs of the RAMOSA3 gene, but why do they have different floral sexualities? My project aims to discover if RA3 has a conserved role in controlling floral organ suppression and inflorescence branching in grasses. I investigated the role of the RA3 homolog in brachypodium using CRISPR/Cas9 and the sodium azide mutant line NaN372. The transformed brachypodium did not have any CRISPR edits. However, NaN372 has an amino acid substitution in the RA3 gene. The mutant phenotype suggests that Bdra3 mutants do not have more flowers than the wild-type, contrary to what I predicted if RA3 function is conserved.



Brachypodium, RAMOSA3, inflorescence branching