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Increase in flavan-3-ols by silencing flavonol synthase mRNA affects the transcript expression and activity levels of antioxidant enzymes in tobacco

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Title Increase in flavan-3-ols by silencing flavonol synthase mRNA
affects the transcript expression and activity levels of
antioxidant enzymes in tobacco
 
Creator Mahajan, M
Joshi, Robin
Gulati, Ashu
Yadav , S K
 
Subject Plant sciences
 
Description Flavonoids are plant secondary metabolites widespread throughout the plant kingdom
involved in many physiological and biochemical functions. Amongst the flavonoids,
flavan-3-ols (catechin and epicatechin) are known for their direct free radical
scavenging activity in vitro, but studies on their antioxidant potential and interaction
with antioxidant enzymes in vivo are lacking. Here, the flavonoid pathway was
engineered by silencing a gene encoding flavonol synthase (FLS) in tobacco to direct
the flow of metabolites towards production of flavan-3-ols. FLS silencing reduced
flavonol content 17–53%, while it increased catechin and epicatechin content 51–
93% and 18–27%, respectively. The silenced lines showed a significant increase in
expression of genes for dihydroflavonol reductase and anthocyanidin synthase, a
downstream gene towards epicatechin production, with no significant change in
expression of other genes of the flavonoid pathway. Effects of accumulation of flavan-
3-ols in FLS silenced lines on transcript level and activities of antioxidant
enzymes were studied. Transcripts of the antioxidant enzymes glutathione reductase
(GR), ascorbate peroxidase (APx), and catalase (CAT) increased, while glutathione-
S-transferase (GST), decreased in FLS silenced lines. Enhanced activity of all the
antioxidant enzymes was observed in silenced tobacco lines. To validate the affect
of flavan-3-ols on the antioxidant system, in vitro experiments were conducted with
tobacco seedlings exposed to two concentrations of catechin (10 and 50 lm) for
2 days. In vitro exposed seedlings produced similar levels of transcripts and activity
of antioxidant enzymes as FLS silenced seedlings. Results suggest that flavan-3-ols
(catechin) might be increasing activity of GR, Apx and CAT by elevating their
mRNAs levels. Since these enzymes are involved in scavenging of reactive oxygen
species, this strategy would help in tailoring crops for enhanced catechin production
as well as making them tolerant to oxidative stresses.
 
Date 2012
 
Type Article
PeerReviewed
 
Format application/pdf
 
Identifier http://ihbt.csircentral.net/1275/1/57_Increase_in_flavan.pdf
Mahajan, M and Joshi, Robin and Gulati, Ashu and Yadav , S K (2012) Increase in flavan-3-ols by silencing flavonol synthase mRNA affects the transcript expression and activity levels of antioxidant enzymes in tobacco. Journal of Plant Biology, 14 (5). pp. 725-733.
 
Relation http://ihbt.csircentral.net/1275/