Biotechnology of Fruit Quality - Fruit Ripening: Physiology, Signalling and Genomics - page 280

fl avonols in ripe tomato fruit was achieved,
mainly due to increased production of
kaempferolin transgenic fruit (Bovy et al. ,
2002; Le Gall et al. , 2003). Expression of
Rosea1 and Delila , transcription factors
that activate the biosynthesis of antho-
cyanin, driven by an E8 promoter resulted
in enhanced anthocyanin production in
tomato pericarp at concentrations com-
parable to that in blackberries and
blueberries (Butelli et al. , 2008). Transgenic
tomato fruit constitutively expressing
ANTHOCYANIN1 ANT1 ), a fl avonoid-
related R2R3-MYB transcription factor, had
higher levels of anthocyanadins including
petunidin, malvidin and delphinidin
(Schreiber et al. , 2012). Downregulation of
TOMATO AGAMOUS-LIKE 1 ( TAGL1 ), a
MADS-box transcription factor, resulted in
lowering the levels of lycopene and
isoprenoids whereas its overexpression
caused higher accumulation of lycopene
and naringenin chalcone (Itkin et al. ,
2009).
Altering the expression of tran-
scriptional regulators of photomorphogenic
responses enhanced the production of
fl avonoids. Fruit-specifi c RNAi-mediated
silencing of DE-ETIOLATED 1 ( DET1 ),
transcriptional repressor of photo-
morphogenic responses, not only increased
carotenoid levels but also increased
fl avonoids by 3.5-fold (Davuluri et al. ,
2005). Constitutive overexpression of
cryptochrome 2 resulted in about a
threefold increase in fl avonoids (Giliberto
et al. , 2005). The fruit-colour tomato
mutant, high-pigment-1 ( hp-1 ), carrying a
mutation in UV-DAMAGED DNA BINDING
PROTEIN 1 ( DDB1 ) increased levels of both
carotenoids and fl avonoids (chlorogenic
acid and rutin) (Long et al. , 2006).
Likewise, RNAi-mediated repression of the
DDB1-interacting protein CUL4 in tomato
lines ( 35S:CUL4-RNAi ) resulted in elevated
levels of anthocyanins and carotenoids
(Wang et al. , 2008).
Transcriptome analysis of high
polyamine-accumulating E8:ySAMdc tom-
ato fruits showed upregulation of the
transcription profi les related to the
carotenoid and fl avonoid

pathways (Mattoo et al. , 2007). A mutation
in PSY-1 (tomato mutant rr ) did not
increase the levels of phenylpropanoids
and fl avonoids (chlorogenic acid, caffeic
acid, p -coumaric acid and ferulic acid) in
pericarp tissues (Long et al. , 2006), but
constitutive overexpression of PSY-1
showed an increase in phenylpropanoids
and fl avonoids including 3-caffeoylquinic
acid, naringenin chalcone and quercetin
derivatives in red-ripe tissues (Fraser et al. ,
2007).
Other studies have highlighted the
importance of the aforementioned strat-
egies in either enhancing the biological
activity of endogenous fl avonoids or
achieving fruit quality attributes, rather
than just enhancement of fl avonoids. For
example, prenylated fl avonoids, derived
from the addition of hydrophobic
molecules to fl avonoids, are biologically
more active than their native forms,
possibly because of the lipophilicity of the
prenyl moiety, which makes fl avonoids
more membrane permeable (Maitrejean et
al. , 2000; Murakami et al. , 2000). Fruit-
specifi c overexpression of Streptomyces
prenyltransferase HypSc in tomato fruit
resulted in the accumulation of
3 c -dimethylallyl naringenin, a prenylated
form of the native naringenin fl avonoid
(Koeduka et al. , 2011). The other example
of achieving an industry-driven objective is
to induce parthenocarpy (Rotino et al. ,
1997; Ficcadenti et al. , 1999; Pandolfi ni et
al. , 2002).
Together, these results provide strong
evidence in favour of biotechnological
interventions not only for enhancing the
levels and composition of health-related
polyphenols in fruits but also to produce
novel compounds by the engineering of
fl avonoid and other pathways (Schijlen et
al. , 2006). Studies on the tomato model
system described above clearly support the
signifi cance of transgenic approaches in
enhancing sensory fruit quality attributes.
Similar approaches have also been adopted
to manipulate fl avonoid biosynthetic
pathways in strawberry (Lunkenbein et al. ,
2006), maize (Sidorenko et al. , 2000; Li et
al. , 2007), grape (Boss et al. , 1996; Bogs et biosynthesis