Regulation of Arabidopsis Floral Organ Development by the Transcription Factor AINTEGUMENTA-LIKE6

Flowers, and the fruits and seeds they produce, are of great agricultural and economic importance. Understanding the molecular mechanisms that mediate the identity, size and arrangement of floral organs within the flower may allow us to tune these elements for increased crop productivity. I examine several potential regulatory targets of the Arabidopsis AINTEGUMENTA-LIKE6 (AIL6) transcription factor that is involved in these processes and I identify protein-protein interactions that may mediate its activity in flowers. As described by the ABCE model, unique floral organ identities are specified in each whorl of the flower by different combinations of homeotic gene activities. Two members of the AINTEGUMENTA-LIKE/PLETHORA (AIL/PLT) transcription factor family, AINTEGUMENTA (ANT) and AIL6, also contribute to floral organ identity in whorls two, three and four. The experiments described here investigate the possible role of AIL6 in regulation of homeotic gene expression. Furthermore, I investigate whether AIL6 can interact with itself and/or other members of the AIL/PLT transcription factor family. I show that AIL6 binds to regulatory regions of the class B and C genes. While activation of an inducible AIL6 transcription factor in ant ail6 flowers partially restores petal, stamen and carpel identity, no immediate effect on expression of the homeotic genes was observed suggesting that their regulation by AIL6 may be indirect. I also find that AIL6 is able to interact with itself and with ANT when transiently expressed in Nicotiana benthamiana leaves. Furthermore, I find evidence that ANT interacts with itself in Arabidopsis flowers. Thus, dimerization may influence the DNA binding activity or specificity of these transcription factors. Flower fertility is critical in agriculture and this family of transcription factors are key regulators of floral organ development. Improving our understanding of the molecular means by which these transcription factors regulate flower development may lead to important advances in crop production or floriculture