Antioxidants and Bioactive Compounds in Fruits - Fruit Ripening: Physiology, Signalling and Genomics - page 112

Fraser et al. , 2009; Águila Ruiz-Sola and
Rodríguez-Concepción, 2012). Additional
evidence has indicated that carotenoid
accumulation in ripening tomato fruit is
under the control of the negative-regulator
APETALA2/ERF gene SlAP2a , opening
new directions for manipulating the
nutritional quality of tomato (Chung et al. ,
2010).
The biosynthetic pathway of ascorbate
has recently been fully characterized
(Smirnoff, 2011). It has also been shown
that AsA accumulation is developmentally
regulated during ripening in tomato
(Ioannidi et al. , 2009), melon (Pateraki et al. ,
2004; Sanmartin et al. , 2007), apple (Davey
et al. , 2004; Li et al. , 2009), blackcurrant
(Hancock et al. , 2007), peach (Imai et al. ,
2009), grape (Cruz-Rus et al. , 2010),
strawberry (Cruz-Rus et al. , 2011) and
kiwifruit (Li et al. , 2010). However,
although AsA is a co-factor of ACC oxidase,
the last enzyme of ethylene biosynthesis, it
is not yet clear whether its biosynthesis is
regulated by ethylene during fruit ripening.
On the other hand, Ioannidi et al. (2009)
found that the only ascorbate biosynthetic
gene that is ethylene regulated is GPP.
Phenylpropanoid accumulation is
developmentally regulated during ripening
in a variety of fruit (Singh et al. , 2010). In
climacteric fruit, ethylene plays the main
role in inducing the biosynthetic genes,
starting from phenylalanine ammonia lyase
and ending with more specialized enzymes
catalysing the formation of various phenols,
fl avonoids, proanthocyanidins and antho-
cyanins. However, in non-climacteric fruit,
abscissic acid seems to play a critical role in
regulating the ripening process and the
accumulation of the products of the
phenylpropanoid pathway (Zifkin et al. ,
2012). It should be noted that this pathway
is controlled by a number of transcription
factors belonging to the MYB family in
combination with basic helix-loop-helix
(bHLH) and WD-40 partners.
Other bioactive compounds, such as,
among others, folates (Waller et al. , 2010;
Hanson and Gregory, 2011) and toco-
pherols (Mélendez-Martinez et al. , 2010),
are also developmentally regulated.

7.5.3 Environmental factors

Cultivation systems and environmental
signals may control the composition of
bioactive compounds, with the most
important environmental factors being
light and temperature. In addition, other
atmospheric factors can be considered: air
carbon dioxide concentration, air humidity
and air pollutants, including ozone (Dorais
et al. , 2008; Vigneault et al. , 2012).
It is known that light quality and
intensity, including UV radiation, can
regulate the accumulation of vitamin C
(Davey et al. , 2000; Davuluri et al. , 2004,
2005; Pateraki et al. , 2004; Smirnoff, 2011;
Alimohammadi et al. , 2012), carotenoids
(Davuluri et al. , 2004, 2005; Fraser et al. ,
2009; Azari et al. , 2010; Águila Ruiz-Sola
and Rodríguez-Concepción, 2012) and
phenylpropanoid compounds (Davuluri et
al. , 2004, 2005; Wang et al. , 2009b; Azari et
al. , 2010). Studies on the interplay of light
and shade have suggested that light
infl uences ascosbate recycling and bio-
synthesis processes of apples, primarily in
the peel and leaf but not in the fl esh (Davey
et al. , 2004; Li et al. , 2009). In tomatoes,
ascorbate accumulation was greatly affected
by high light intensity (Gautier et al. , 2009),
which seems to be regulated by the expres-
sion of GGP and GPP (Massot et al. , 2012).
Interestingly, a recent study suggested that a
different light composition controls the
accumulation of distinctive phenypropa-
noid compounds; that is, proanthocyanidin
biosynthesis and composition were
stimulated primarily by visible light,
whereas fl avonols were specifi cally trig-
gered by UV light (Koyama et al. , 2012).
In terms of carotenoids, it has been
shown that light is an important factor
affecting the expression of biosynthetic
genes, but also that light regulates their
accumulation by controlling the light-
signalling apparatus (Azari et al. , 2010;
Águila Ruiz-Sola and Rodríguez-
Concepción, 2012). Within this context,
four different types of light-responsive
promoter elements were detected in all
ascorbate-related genes in Arabidopsis
(Ioannidi et al. , 2009). One light-responsive