| Abstract Detail
Metabolism Manabe, Yuzuki [1], Miki, Brian [2]. Branched-Chain Amino Acids Are Required for All Stages of Plant Development Including Gametophytes Function. CSR1 encodes the catalytic subunit of acetohydroxyacid synthase, the enzyme catalyzing the first committed step of branched-chain amino acid (BCAAs) biosynthesis in Arabidopsis thaliana. imidazolinone (IM), a CSR1 inhibitor, inhibits both shoot and root growth and is fatal to wildtype (WT) plants, but does not inhibit growth of csr1-2D. Affymetrix ATH1 microarrays have demonstrated that IM does not alter the transcriptome profile of csr1-2D, and there were no significant changes detected in csr1-2D compared to WT. These results indicate that CSR1 is the sole target of IM, and that the csr1-2D mutation has little or no detrimental effect on whole-plant fitness. WT and csr1-2D were micro-grafted to test the long distance transport of IM, BCAAs, and root growth signaling molecules. Either combination of chimeric plants survived longer than WT, and root growth was inhibited by IM if the stock is WT, regardless of scion genotype. This indicates that root growth is regulated locally, and neither csr1-2D scion nor stock is sufficient to rescue the entire plant. We hypothesize that BCAAs are not transported, while IM is transported from roots to shoots. Two putative CSR1 loss-of-function mutants, csr1-7 and csr1-8, obtained from T-DNA collections are dominant lethal. In both alleles, progenies of a heterozygous plant segregate closer to a 1:2 (Heterozygous: Homozygous WT) than the expected ratio of 2:1, indicating that not only zygotes but also gametophytes are defective in the mutants. The phenotypes of csr1-7 and csr1-8, along with the results from grafting experiments indicate that there is no long-distance transport of either CSR1 or BCAAs, and that CSR1 expression is essential at the site of BCAA consumption.
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Related Links:
Miki Lab.
1 - Agriculture and Agri-Food Canada, Bioproducts and Bioprocesses, Research Branch, Room 4017B, KW Neatby Bldg, 960 Carling Ave, Ottawa, ON, K1A 0C6, Canada
2 - Agriculture and Agri-Food Canada, Bioproducts and Bioprocesses, Research Branch
Keywords:
Branched-chain amino acid biosynthesis
Arabidopsis thaliana
CSR1
Acetohydroxyacid synthase (AHAS)
Imidazolinone.
Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P19010
Abstract ID:287 |
