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Phenylalanine ammonia-lyase (EC 4.3.1.5) from Pinus banksiana: partial cDNA cloning and effect of exogenously supplied trans-cinnamic acid on elicitor-inducible expression Lam, Monica Lee
Abstract
Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), the "entrypoint enzyme" of the phenylpropanoid pathway, catalyzes the conversion of L-phenylalanine to trans-cinnamic acid and is an important bridge between primary and secondary metabolism in plants. In many angiosperms, PAL exists as multiple isoforms, encoded by a gene family. PAL has been characterized from two gymnosperms, Pinus banksiana and Pinus taeda, and one form of the enzyme is present. The regulation of constitutive and inducible PAL expression is not well understood. From studies employing angiosperms, transcriptional control appears to be important, and modulation of PAL activity by trans-cinnamic acid has also been proposed. The objectives of this study were to investigate the genomic organization of PAL and the role of transcriptional and metabolic regulation of PAL in a gymnosperm. PAL activity is transiently increased in P. banksiana cell suspension cultures treated with an ectomycorrhizal fungal elicitor preparation. Preliminary results indicated that increases in PAL transcripts precede and are closely correlated with the PAL induction. Thus this system was convenient for constructing a cDNA library enriched in PAL sequences, and for studying the regulation of inducible PAL expression. Six partial PAL cDNA clones (0.2 to 1.8kb) were isolated from a library prepared from elicitor-treated P. banksiana cell cultures. In overlapping regions, the cDNA sequences are highly similar, but not identical, suggesting that multiple genes may encode PAL in P. banksiana. Extensive homology to the P. taeda PAL cDNA sequence was also observed. The chemical environment of elicitor-treated cells was manipulated by exogenously supplying frans-cinnamic acid. Hybridization of a P. banksiana partial PAL cDNA with total RNA slot blots was used to monitor PAL transcript levels. Supplying frans-cinnamic acid delayed the increase in PAL transcript levels and completely inhibited the induction of PAL activity normally associated with elicitor treatment. This suggests trans-cinnamic acid can downregulate PAL expression, although further study is required to determine the specificity of its action. This work represents the first study of the metabolic regulation of PAL in a gymnosperm species.
Item Metadata
Title |
Phenylalanine ammonia-lyase (EC 4.3.1.5) from Pinus banksiana: partial cDNA cloning and effect of exogenously supplied trans-cinnamic acid on elicitor-inducible expression
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
1996
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Description |
Phenylalanine ammonia-lyase (PAL; EC 4.3.1.5), the "entrypoint enzyme" of the phenylpropanoid
pathway, catalyzes the conversion of L-phenylalanine to trans-cinnamic acid and is an important bridge
between primary and secondary metabolism in plants. In many angiosperms, PAL exists as multiple
isoforms, encoded by a gene family. PAL has been characterized from two gymnosperms, Pinus banksiana
and Pinus taeda, and one form of the enzyme is present. The regulation of constitutive and inducible PAL
expression is not well understood. From studies employing angiosperms, transcriptional control appears
to be important, and modulation of PAL activity by trans-cinnamic acid has also been proposed.
The objectives of this study were to investigate the genomic organization of PAL and the role of
transcriptional and metabolic regulation of PAL in a gymnosperm. PAL activity is transiently increased in
P. banksiana cell suspension cultures treated with an ectomycorrhizal fungal elicitor preparation. Preliminary
results indicated that increases in PAL transcripts precede and are closely correlated with the PAL induction.
Thus this system was convenient for constructing a cDNA library enriched in PAL sequences, and for
studying the regulation of inducible PAL expression.
Six partial PAL cDNA clones (0.2 to 1.8kb) were isolated from a library prepared from elicitor-treated
P. banksiana cell cultures. In overlapping regions, the cDNA sequences are highly similar, but not identical,
suggesting that multiple genes may encode PAL in P. banksiana. Extensive homology to the P. taeda PAL
cDNA sequence was also observed. The chemical environment of elicitor-treated cells was manipulated by
exogenously supplying frans-cinnamic acid. Hybridization of a P. banksiana partial PAL cDNA with total
RNA slot blots was used to monitor PAL transcript levels. Supplying frans-cinnamic acid delayed the
increase in PAL transcript levels and completely inhibited the induction of PAL activity normally associated
with elicitor treatment. This suggests trans-cinnamic acid can downregulate PAL expression, although
further study is required to determine the specificity of its action. This work represents the first study of the
metabolic regulation of PAL in a gymnosperm species.
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Extent |
7570821 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-02-02
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0087024
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
1996-05
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.