Early genetic events in the interaction of Verticillium dahliae and Gossypium species /
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| Other Authors: | , |
| Format: | Thesis Book |
| Language: | English |
| Published: |
1993.
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| Subjects: | |
| Online Access: | ProQuest, Abstract Link to OAKTrust copy |
| Abstract: | Verticillium dahliae is a soilborne fungus which invades the vascular system of plants to cause verticillium wilt disease. Gossypium barbadense (cotton) plants possess a resistance to verticillium wilt which is multigenic and additive. Patterns of structural gene regulation in the first six days after inoculation with V. dahliae in resistant G. barbadense were compared to patterns in susceptible Gossypium hirsutum. Coding regions of selected structural genes, amplified from the cotton genome by polymerase chain reaction using mixed oligonucleotide primers, were used as probes of the messenger RNA of challenged and control plants. The activation of a gene coding for an enzyme, 3-hydroxy-3-methylglutaiyl CoA reductase (HMGR), required to supply precursor molecules to the terpenoid anabolic pathway, is necessary for the accumulation of terpenoid phytoalexins. This gene is activated earlier after inoculation in resistant plants, allowing a more rapid and effective defense response. HMGR is also down-regulated earlier in resistant plants, protecting plant tissues from continued exposure to phytoalexins. The more effective response of resistant plants is due to their ability to activate the phytoalexin pathway in response to conidial cells in xylem, while susceptible plants activate this pathway only after conidia have had time to germinate to hyphae. Chalcone synthase is an enzyme of the flavonoid pathway which leads to tannins. Activation of the gene for chalcone synthase is necessary in cotton plants for tannin production in response to infection and is more rapid in resistant plants. Phenylalanine ammonia lyase is necessary to supply precursors to the flavonoid pathway and while the gene for this enzyme is expressed constitutively in cotton stem tissue, it is suppressed after infection with V. dahliae in both resistant and susceptible plants. A gene encoding β-1,3-glucanase is expressed constitutively in cotton stems and shows little or no response to infection, and activation of the gene for chitinase is much more extensive in susceptible plants. No expression of glutamine synthetase genes, which might function to counteract suspected ammonium ion toxicity by V. dahliae, was detected in cotton stem tissue. |
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| Item Description: | Vita. "Major subject: Genetics." |
| Physical Description: | vii, 78 leaves : illustrations ; 28 cm |
| Bibliography: | Includes bibliographical references. |