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The raz1 mutant of Arabidopsis thaliana lacks the activity of a high-affinity amino acid transporter

Authors
  • Verbruggen, Nathalie
  • Borstlap, AC
  • Jacobs, M
  • Van Montagu, Marc
  • Messens, Eric
Publication Date
Jan 01, 1996
Source
Ghent University Institutional Archive
Keywords
Language
English
License
Unknown
External links

Abstract

The raz1 mutant of Arabidopsis thaliana (L.) Heynh. has been selected as resistant to the toxic proline analogue, azetidine-2-carboxylic acid (2AZ). Seedlings of the mutant tolerated fivefold higher concentrations of 2AZ (ED(50) = 0.25 mM) than the wild-type seedlings (ED(50) = 0.05 mM). The mutant gene was found to be semi-dominant and the corresponding RAZ1 locus was mapped on chromosome 5 at 69.6 +/- 1.8 cM. The resistance to 2AZ could be fully and exclusively accounted for by the lower uptake rate of the proline analogue in the mutant. The influx of L-proline in roots of wild-type seedlings could be dissected into two components: (i) a component with a high affinity and a low capacity for L-proline (K-m approximate to 20 mu M, V-max approximate to 60 nmol .(g FW)(-1). h(-1)) and also a high affinity for r-2AZ (K-i approximate to 40 mu M) and (ii) a low-affinity, high-capacity component (K-m approximate to 5 mM: V-max = 1300 nmol .(g FW)(-1). h(-1)). Clearly, the raz1 mutation affects the activity of a high-affinity transporter, because the high-affinity uptake of proline in the mutant was at least fivefold lower than in the wild-type, whereas the low-affinity uptake was unchanged.

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