Structural requirements necessary for auxin activity




Dharmasiri, Nihal

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Auxin, a major hormone, controls the plant growth and development. While Indole acetic acid (IAA) is the major natural auxin in plants, many synthetic chemicals with diverse structures possess auxinic activity. IAA promotes the interaction between TIR1 and Aux/IAA proteins. This auxin induced interaction between TIR1 and Aux/IAA proteins can be demonstrated in an in vitro assay. We used this in vitro assay along with root growth assay, 1) to distinguish between chemicals that promote TIR1 Aux/IAA interaction and 2) to understand molecular structure that is necessary for auxinic activity. We tested many chemicals, including 2,4-D, 2,4,5-T, MCPA, phenoxy acetic acid, dicamba, picloram, IBA, IAA and its conjugates for auxinic activity. In brief, our results indicate that presence of a ring structure and COO- group is an essential characteristic of an auxin. Presence of CH3 and Cl- groups on the ring heavily influences the auxinic activity of the chemical. It is evident that picloram, a widely used herbicide, functions differently from IAA. Six students (5 undergraduates and one graduate) were trained using the REP funds. While two students presented their findings at the Annual Colloquium of the Department of Biology, undergraduate Cameron Collier won the runner-up for the best presentation. Additionally, findings were also presented at the 2006 FASEB conference on plant developmental biology, an international conference on plant biology. Based on the preliminary results, a proposal was submitted to the NSF. Proposal was not funded (but was recommended for funding). A revised proposal will be submitted in 2007. A manuscript is also in preparation.


Research Enhancement Program Final Report


Auxin, indole acetic acid, IAA, auxinic activity, TIR1, Aux/IAA proteins


Dharmasiri, N. (2006). <i>Structural requirements necessary for auxin activity</i>. Research Enhancement Program, Texas State University, San Marcos, TX.


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