Phenylalanine ammonia-lyase (PAL) and cinnamate 4-hydroxylase (C4H) and catechins (flavan-3-ols) accumulation in tea
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Phenylalanine ammonia-lyase and cinnamate 4-hydroxylase are important enzymes in allocating significant amounts of carbon from phenylalanine into the biosynthesis of several important secondary metabolites. Tea is an important crop of commerce known for its beverage and medicinally important flavonoid compounds, mainly catechins. As metabolic flux for the operation of the flavonoid pathway is maintained through the activities of PAL and C4H, thus, catechins biosynthesis in tea is critically dependent on the products of these enzymes. We examined the expression of PAL and C4H. Sequence encoding CsPAL was isolated from tea by polymerase chain reaction using sequence information available at the NCBI GenBank. Sequence encoding C4H was isolated from tea by using differential display of mRNA and rapid amplification of cDNA ends technology. CsC4H (AY641731) comprised of 1,352 bp full-length cDNA with open reading frame of 1,173 bp encoding 390 amino acids. Catechin contents decreased in response to drought stress (DS), abscisic acid (ABA), and gibberellic acid (GA3) treatments but increased in response to wounding. The expression of CsPAL and CsC4H showed the same behavior under the above treatments and was also in accordance with the catechin contents. A positive correlation between catechin contents and gene expression suggested a critical role of the enzymes in catechins biosynthesis and a crosstalk between phenylpropanoid and flavonoid pathways.
KeywordsPhenylalanine ammonia-lyase Cinnamate 4-hydroxylase Differential display Expression analysis Catechins Tea
Camellia sinensis C4H
Camellia sinensis PAL
rapid amplification of cDNA ends
The authors are thankful to the Council of Scientific and Industrial Research (CSIR), India for funding the present research work under the New Millennium Indian Technology Leadership Initiative (NMITLI) program entitled “Using functional genomics in plants: development and use of technologies for gene discovery and expression modulation—niche pathway engineering in tea.” KS is thankful to CSIR for awarding the junior and senior research fellowships. The technical help provided by Mr. Digvijay Singh for gene sequencing is duly acknowledged.
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