Agriculture Reference
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vitamin A (Enfi ssi et al. , 2010; Tranbarger
et al. , 2011; Hyun et al. , 2012; Schweiggert
et al. , 2012), vitamin E (Almeida et al. ,
2011) and vitamin C (Stevens et al. , 2007;
Bulley et al. , 2009; Garcia et al. , 2009;
Cruz-Rus et al. , 2011) through bio-
technological means or marker-assisted
breeding. Although current studies are
focused mostly on model fl eshy fruit
species like tomato, these strategies should
soon become relevant to species for which
wide genetic diversity exists in terms of
vitamin content (e.g. papaya; Schweiggert
et al. , 2012) and/or that are easily genetic-
ally transformable. The overwhelming
development of new and cheap sequencing
strategies allowing a complete inventory of
expressed genes and deciphering of whole-
genome sequences will help considerably
in advancing these studies.
However, one must keep in mind that
alterations of provitamin A, vitamin E and
vitamin C biosynthesis may have profound
repercussions on whole-plant physiology
and on fruit quality. As an example, the
isoprenoid and carotenoid pathways are
involved in the formation not only of
provitamin A and vitamin E but also of
several major plant hormones such as
gibberellin and ABA (Fig. 8.1) and of
carotenoid-derived volatiles (Lewinsohn et
al. , 2005; Mathieu et al. , 2009; Vogel et al. ,
2010). In addition to increasing the
carotenoid level, the constitutive over-
expression of the Psy-1 gene in tomato
affected plant vigour and isoprenoid-
derived hormones in vegetative tissues, as
well as fruit chlorophyll and tocopherol
levels (Fraser et al. , 2009). Conversely,
fruit-specifi c silencing of the SlNCED1
gene involved in ABA biosynthesis, which
effectively reduced ABA accumulation in
tomato fruit, also led to the enhancement
of tomato fruit lycopene and E -carotene
levels (Sun et al. , 2012). Silencing of GME,
a key enzyme of ascorbate biosynthesis,
affected both tomato fruit vitamin content
and fi rmness (Gilbert et al. , 2009), thereby
demonstrating the tight connections
between vitamin C and cell-wall bio-
synthesis and between fruit nutritional
and sensorial quality. For genetic
engineering of fruit vitamin levels, it is
therefore essential to use fruit-specifi c
promoters, as was done for the DET1 and
CUL4 genes involved in light signalling
(Wang et al. , 2008; Enfi ssi et al. , 2010) and
for tocotrienol engineering in tomato fruit
(our unpublished results), or, when using
natural or artifi cially induced genetic
variability, to fi nd alleles that have no
detrimental effects on plant and fruit.
References
Abushita, A.A., Daood, H.G. and Biacs, P.A. (2000) Change in carotenoids and antioxidant vitamins
in tomato as a function of varietal and technological factors. Journal of Agricultural and Food
Chemistry 48, 2075-2081.
Agius, F., Gonzalez-Lamothe, R., Caballero, J.L., Munoz-Blanco, J., Botella, M.A. and Valpuesta, V.
(2003) Engineering increased vitamin C levels in plants by overexpression of a D -galacturonic
acid reductase. Nature Biotechnology 21, 177-181.
Alba, R., Cordonnier-Pratt, M.-M. and Pratt, L.H. (2000) Fruit-localized phytochromes regulate
lycopene accumulation independently of ethylene production in tomato. Plant Physiology 123,
363-370.
Alba, R., Payton, P., Fei, Z.J., McQuinn, R., Debbie, P., Martin, G.B., Tanksley, S.D. and Giovannoni,
J.J. (2005) Transcriptome and selected metabolite analyses reveal multiple points of ethylene
control during tomato fruit development. Plant Cell 17, 2954-2965.
Almeida, J., Quadrana, L., Asís, R., Setta, N., de Godoy, F., Bermúdez, L., Otaiza, S.N., Corrêa da
Silva, J.V., Fernie, A.R., Carrari, F. and Rossi, M. (2011) Genetic dissection of vitamin E
biosynthesis in tomato. Journal of Experimental Botany 62, 3781-3798.
Alquezar, B., Rodrigo, M.J. and Zacarias, L. (2008) Regulation of carotenoid biosynthesis during fruit
maturation in the red-fl eshed orange mutant Cara Cara. Phytochemistry 69, 1997-2007.
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