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Defence related lignin deposition in wheat (Triticum aestivum L.)

Defence related lignin deposition in wheat (Triticum aestivum L.)
Defence related lignin deposition in wheat (Triticum aestivum L.)

Lignin deposition following fungal challenge or elicitor treatment is a structural plant defence against filamentous fungi in wheat (Tritium aestivum L.). The aim of the present study was to investigate the involvement of two key enzymes, phenylalanine ammonia lyase (PAL, EC 4.3.1.5) and cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195), in the expression of this defence response.

A range of potential CAD specific inhibitors were developed and their potency against the three major forms of wheat CAD was investigated. The most effective inhibitors were the zinc chelating substrate analogues 4-hydroxy-a-mercapto-3-methoxyciannamic acid (HMMCA), ethyl m-anisoylacetate (EAA) and the suicide inhibitor trans-2-(4-hydroxy-3,5-dimethyoxyphenyl)-cyclopropane-1-methanol (HDCPM), demonstrating a correlation between substrate analogy and increased inhibition. Furthermore, HMMCA, EAA, 2,2'-dipyridyl and HDCPM were shown to reduce lignin accumulation in elicitor-treated wheat leaves. This work may provide the opportunity to develop CAD specific inhibitors that may be used as tools to study the role of defensive lignification in wheat.

A novel PAL gene (gPAL) was isolated from a cDNA library constructed from elicitor-treated wheat leaves. Using cytogenetical analysis this PAL was mapped to chromosome 6 in wheat. Northern analysis demonstrated that small increases in PAL transcription are correlated with elicitor treatment. Furthermore, this increase precedes defence related lignin deposition in wheat leaves.

Using a PCR strategy to isolate CAD from elicitor-treated wheat leaf tissue lead to the isolation of novel sequence. Alignment of this sequence with known CAD sequences enabled the identification of structural motifs conserved amongst zinc containing, long chain alcohol dehydrogenases (ADH). Interestingly, divergent residues generally occurred at the same positions as observed between CAD genes and the closely related elicitor inducible genes (ELI). Transcripts homologous to this novel ADH cDNA accumulated in wheat leaves following elicitor-treatment. The timing of mRNA accumulation correlates with the time observed for inducible CAD activity.

University of Southampton
Hall, Sharon Anita
a0c7ae60-288a-4ec9-adff-8d6cfd649895
Hall, Sharon Anita
a0c7ae60-288a-4ec9-adff-8d6cfd649895

Hall, Sharon Anita (1998) Defence related lignin deposition in wheat (Triticum aestivum L.). University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

Lignin deposition following fungal challenge or elicitor treatment is a structural plant defence against filamentous fungi in wheat (Tritium aestivum L.). The aim of the present study was to investigate the involvement of two key enzymes, phenylalanine ammonia lyase (PAL, EC 4.3.1.5) and cinnamyl alcohol dehydrogenase (CAD, EC 1.1.1.195), in the expression of this defence response.

A range of potential CAD specific inhibitors were developed and their potency against the three major forms of wheat CAD was investigated. The most effective inhibitors were the zinc chelating substrate analogues 4-hydroxy-a-mercapto-3-methoxyciannamic acid (HMMCA), ethyl m-anisoylacetate (EAA) and the suicide inhibitor trans-2-(4-hydroxy-3,5-dimethyoxyphenyl)-cyclopropane-1-methanol (HDCPM), demonstrating a correlation between substrate analogy and increased inhibition. Furthermore, HMMCA, EAA, 2,2'-dipyridyl and HDCPM were shown to reduce lignin accumulation in elicitor-treated wheat leaves. This work may provide the opportunity to develop CAD specific inhibitors that may be used as tools to study the role of defensive lignification in wheat.

A novel PAL gene (gPAL) was isolated from a cDNA library constructed from elicitor-treated wheat leaves. Using cytogenetical analysis this PAL was mapped to chromosome 6 in wheat. Northern analysis demonstrated that small increases in PAL transcription are correlated with elicitor treatment. Furthermore, this increase precedes defence related lignin deposition in wheat leaves.

Using a PCR strategy to isolate CAD from elicitor-treated wheat leaf tissue lead to the isolation of novel sequence. Alignment of this sequence with known CAD sequences enabled the identification of structural motifs conserved amongst zinc containing, long chain alcohol dehydrogenases (ADH). Interestingly, divergent residues generally occurred at the same positions as observed between CAD genes and the closely related elicitor inducible genes (ELI). Transcripts homologous to this novel ADH cDNA accumulated in wheat leaves following elicitor-treatment. The timing of mRNA accumulation correlates with the time observed for inducible CAD activity.

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Published date: 1998

Identifiers

Local EPrints ID: 463568
URI: http://eprints.soton.ac.uk/id/eprint/463568
PURE UUID: 3f36cc56-4e58-4187-abba-ba4ae74e3f8d

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Date deposited: 04 Jul 2022 20:53
Last modified: 23 Jul 2022 02:15

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Contributors

Author: Sharon Anita Hall

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