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A study of IAA conjugate physiology in Arabidopsis thaliana

Campanella, James Joseph
http://rave.ohiolink.edu/etdc/view?acc_num=case1062083413

Abstract Details

1996, Doctor of Philosophy, Case Western Reserve University, Biology.
To identify genes involved in auxin conjugate hydrolysis, we selected Arabidopsis thaliana mutants resistant to growth inhibition by IAA-phenylalanine (IAA-phe). Two IAA conjugate resistant mutants were isolated: icr1 and icr2. Neither of these strains appears to be a conjugate uptake mutant. Dose-response experiments have shown that the mutants are approximately 2- to 3-fold more resistant to IAA-phe and 3-fold more resistant to IAA-alanine than wild-type plants. Although IAA-aspartate is not a strong growth inhibitor of Arabidopsis, the mutants are ∼2-fold more resistant than wild-type plants at 250-1000 mM of IAA-aspartate. Conjugate hydrolysis experiments indicate that icr1 and icr2 hydrolyte at least as well as wild-types. The icr1 mutation is a homozygous, incompletely dominant trait and maps to the top of Chromosome V. The Arabidopsis strain carrying icr1 demonstrates two additional mutations: delayed germination and early flowering. Analysis of a backcross of icr1 to Ws showed that additional traits are not caused by icr2. The late germination trait demonstrates some genetic linkage to the icr1 locus. We have also used a microbial selection scheme as a separate approach to isolating the genes for conjugate hydrolysis. From an Arabidopsis cDNA library we selected a transformed yeast strain able to utilize IAA-phe as a source of phenylalanine. The 1800 bp cDNA from this transformed strain was found to be an exact match to Arabidopsis actin2. Plasmid loss was shown to be accompanied by an inability of the yeast to utilize IAA-phe. Furthermore, down-regulation of the yeast promoter driving actin expression resulted in an inability of the transformed yeast to grow on IAA-phe, indicating expression of the actin is required for growth on this conjugate. IAA-aspartate and IAA-valine also supported growth of the appropriate yeast strains transformed with Arabidopsis actin. Overexpression of yeast actin also allowed auxotrophs to survive on conjugate, indicating that the hydrolysis phenomenon is not limited to Arabidopsis actin. Conjugate hydrolysis assays using actin-transformed and-untransformed yeast demonstrated that although the IAA-bound amino acid was freed by the endogenous hydrolytic enzyme, the IAA is not released intact but is degraded in the process
Christopher Town (Advisor)
218 p.
Biology, Plant Physiology
Conjugate physiology; Arabidopsis thaliana

Recommended Citations

Citations

  • Campanella, J. J. (1996). A study of IAA conjugate physiology in Arabidopsis thaliana [Doctoral dissertation, Case Western Reserve University]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=case1062083413

    APA Style (7th edition)

  • Campanella, James. A study of IAA conjugate physiology in Arabidopsis thaliana. 1996. Case Western Reserve University, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=case1062083413.

    MLA Style (8th edition)

  • Campanella, James. "A study of IAA conjugate physiology in Arabidopsis thaliana." Doctoral dissertation, Case Western Reserve University, 1996. http://rave.ohiolink.edu/etdc/view?acc_num=case1062083413

    Chicago Manual of Style (17th edition)

case1062083413
649
© 1996, all rights reserved.
This open access ETD is published by Case Western Reserve University School of Graduate Studies and OhioLINK.