Abstract: Flavonoids are widespread throughout
the plant kingdom and present in different parts
of plants. Tea (Camellia sinensis) is well known
for very high content of flavonoids especially
flavan-3-ols antioxidants and is an aluminium
(Al) accumulator plant. Dihydroflavonol
4-reductase (DFR) and anthocyanidin reductase
(ANR) are known to be regulatory enzymes of
flavonoid biosynthetic pathway. In this study,
cDNA encoding DFR (CsDFR) and ANR
(CsANR) from tea were overexpressed
individually in tobacco to check their influence on
accumulation of flavonoid contents and
antioxidant potential in roots of transgenic
tobacco. Root morphological features, such as
total volume and the number of lateral roots were
improved in CsDFR and CsANR overexpressing
tobacco plants relative to control tobacco plants.
Both types of transgenic showed higher content
of flavonoids and proanthocyanidins and lower
content of anthocyanins in the roots compared to
roots of control tobacco. Among flavan-3-ols,
only epigallocatechin was observed in the roots
and its content was higher in CsDFR and CsANR
overexpressing tobacco as compared to control
tobacco. Expression of genes encoding various
other enzymes of flavonoid pathway like
Phenylalanine ammonia-lyase, Chalcone
isomerase, Flavanol synthase and Anthocyanin
synthase was increased in roots of CsDFR and
CsANR overexpressing tobacco plants as
compared to control tobacco. The antioxidant
potential of root portion of CsDFR and CsANR
transgenic tobacco plants was found to be
increased as indicated by enhanced total free
radical scavenging activity and tolerance against
Al toxicity. Taken together, these changes in
roots of CsDFR and CsANR transgenic tobacco
provided tolerance to aluminum toxicity