| Abstract Detail
Secondary Metabolism - Afternoon Kidd, Sarah [1], Melillo, Amanda [2], Lu, Rong-He [3], Reed, Deborah [4], Norihito, Kuno [5], Uchida, Kenko [5], Furuya, Masaki [5], Jelesko, John [6]. The A and B loci regulate a complex network of alkaloid biosynthetic and stress response genes in Nicotiana tabacum. NICOTINE biosynthesis in Nicotiana tabacum is under genetic control by the A and B loci. Plants containing semi-dominant mutations at both the A and B loci (i.e. aabb genotype) have lower nicotine levels, reduced nicotine biosynthetic enzyme activities, and reduced mRNA levels of the corresponding biosynthetic genes. The A and B loci therefore appear to be coordinate regulators of several nicotine biosynthetic genes and define a group of co-regulated genes called the A-B regulon. To investigate the composition of genes in the A-B regulon, a fluorescent differential display (FDD) screen was used to randomly sample the transcriptomes of wild type and mutant aabb roots. Over 42,000 transcripts were sampled, resulting in the isolation of 64 FDD clones, representing 49 unique genes or gene families. Four genes associated with nicotine biosynthesis were identified, whereas most of the other FDD clones were homologous with an assortment of stress response genes. In order to confirm and characterize the differential mRNA accumulation levels of these genes, QRT-PCR was performed on RNA isolated from independent primary root cultures. Thirty three genes or gene families showed reproducible aabb genotype effects, representing seven distinct mRNA expression patterns in response media treatments that increase the mRNA levels of known alkaloid biosynthetic genes. Thus, the A and B loci regulate the mRNA levels of some target genes differently than others. Eleven genes or gene families showed only treatment-specific effects, representing four mRNA accumulation patterns. These results demonstrate that all known nicotine biosynthetic genes are under genetic control by the A and B loci. However, the A-B regulon is not limited to only alkaloid biosynthetic genes. Thus, the A-B regulon is more accurately defined as a complex network of differentially expressed stress response genes that include nicotine biosynthetic genes.
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Jelesko Web Page
1 - Thomas Jefferson University, Dept. of Molecular Cell Biology, 1020 Locust St., 229 JAH, Philadelphia, PA, 19107-6799, USA.
2 - Albany Medical College, Dept. of Microbiology, Immunology, and Molecular Genetics, 47 New Scotland Ave, Albany, NY, 12208, USA
3 - Virginia Polytechnic Institute and State University, Plant Pathology, Physiology, and Weed Science Department, Fralin Biotechnology Center, West Campus Drive, Blacksburg, Plant Pathology, Physiology, and Weed Science Depa, 24061-0346, USA
4 - Virginia Polytechnic Institute and State University, Plant Pathology, Physiology, and Weed Science Department, Fralin Biotechnology Center, West Campus Drive, Blacksburg, VA, 24061-0331, USA
5 - Advanced Research Laboratories, Hitachi, Limited, Hatoyama, Saitama, 350-0395, JAPAN
6 - Virginia Polytechnic Institute and State University, Plant Pathology, Physiology, and Weed Science, Fralin Biotechnology Center, West Campus Drive, Blacksburg, VA, 24061-0346, USA
Keywords:
alkaloid biosynthesis
nicotine
genetic regulation
transcriptional profiling
Quantitative Real Time PCR (QRT-PCR)
regulon.
Session: SAT10-6
Location: Hall of Ideas Room F/Monona Terrace
Date: Wednesday, July 26th, 2006
Time: 4:30 PM
Abstract ID:244 |
