Characterizing the Role of the B-class Gene APETALA3 in a Rue-Anemone Mutant

Different combinations of transcription factors from the three gene classes of the Floral ‘ABC’ Model control the development of the four whorls of floral organs: sepals, petals, stamens, and carpels. The B-class gene, APETALA3 (AP3), has been shown in model plants such as Arabidopsis to be necessary for the formation of petals and stamens. In mutants with AP3 knocked-out, flowers develop only two whorls of sepals and two whorls of carpels. The species Thalictrum thalictroides, lacks true petals even though the three paralogs of AP3 (AP3-1, AP3-2a and AP3-2b) are expressed in the petaloid sepals and stamens. I will be using a forward genetics approach to study a horticultural mutant of T. thalictroides, ‘Betty Blake.’ The phenotype of ‘Betty Blake’ consists of multiple whorls of green sepals (non-petaloid) and multiple whorls of carpel, similar to AP3 Arabidopsis knock-outs. We hypothesize that the converted carpels and non-petaloid sepals in ‘Betty Blake’ are due to one or more dysfunctional AP3s. I will extract genomic DNA from ‘Betty Blake,’ PCR amplify and clone AP3-1, AP3-2a and AP3-2b, then compare the AP3 gene sequences from ‘Betty Blake’ to the AP3 gene sequences of the wild type. If our hypothesis is correct, I expect to observe mutations in one or more of the ‘Betty Blake’ AP3s. Such mutations could support the role of AP3s in stamen development, and also account for the petaloidy of sepals in T. thalictroides.