Identification and molecular characterization of two novel Arabidopsis mutants that are resistant to auxin
Date
2009-08
Authors
Siriwardana, Chamindika
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Abstract
Auxin is a pivotal plant hormone that plays a major role in plant growth and development. While indole-3-acetic acid (IAA) is the major natural auxin found in plants, there are many synthetic chemicals with auxinic activity. 1-Naphthylacetic acid (1-NAA), 2, 4-dichlorophenoxyacetic acid (2, 4-D) and picloram are some examples of synthetic auxins. Of these, 2, 4-D and picloram are commonly used as herbicides in agriculture. While both natural and synthetic chemicals exhibit similar effects on plants, these chemicals are structurally different. Whether these structurally different chemicals function through similar molecular mechanisms is not known. Initial work in our laboratory indicates that picloram may function differently from other commonly known auxins. To identify genes that are associated with the picloram response, we used a forward genetics approach to isolate ethyl methanesulfonate (EMS) mutagenized Arabidopsis mutants (pie mutants) that were resistant to picloram.
The objective of the research project was to characterize the Arabidopsis mutants pic59 and pic115 which exhibit altered response to auxin and to isolate the mutant genes by map-based cloning. Both pic59 and pic115 mutants are morphologically very similar to the wild type Col-0 plants with the exception of the short siliques in mutants. The primary root growth of pic59 exhibits differential responses to different auxins. While pic59 is highly resistant to picloram and indole butyric acid (IBA) and slightly resistant to 2, 4-D, it is sensitive to IAA. pic115 is slightly resistant to IAA but sensitive to IBA. The primary root growth of both pic59 and pic115 is resistant to the plant stress hormone abscisic acid (ABA), but is sensitive to the ethylene precursor ACC and to cytokinin (kinetin). Expression of DR5.·GFP transgene in response to different auxins is impaired in pic59 and pi115 backgrounds, suggesting that auxin-dependent gene transcription is affected in both these mutants. Degradation of HS
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Keywords
plants, arabidopsis, mutation, molecular cloning, auxin
Citation
Siriwardana, C. (2009). Identification and molecular characterization of two novel Arabidopsis mutants that are resistant to auxin (Unpublished thesis). Texas State University-San Marcos, San Marcos, Texas.