Agriculture Reference
In-Depth Information
2
Fruit Ripening: Primary Metabolism
Sonia Osorio
1,2
and Alisdair R. Fernie
1
*
Golm, Germany;
2
IHSM-UMA-CSIC, Universidad de Málaga,
Málaga, Spain
2.1 Introduction
Developing tools that allow com-
prehensive phenotyping at the level of the
transcriptome (Alba
et al
., 2005; Vriezen
et
al
., 2008; Matas
et al
., 2011; Rohrmann
et
al
., 2011), proteome (Lee
et al
., 2004; Rose
et al
., 2004; Saravanan and Rose 2004) and
metabolome (Fait
et al
., 2008; Lombardo
et
al
., 2011) enable us to get a detailed view
of the metabolic network (Carrari
et al
.,
2006; Deluc
et al
., 2007; Grimplet
et al
.,
2007; Enfi ssi
et al
., 2010; Zamboni
et
al
., 2010; Osorio
et al
., 2011; Rohrmann
et al
., 2011), and the likely outcome of
taking such an approach is a better
understanding of the metabolic regulation
underlying fruit development. This chapter
will concentrate on central carbon
metabolism, as this is the subject of the
majority of the authors' own research.
Fruit ripening is a complex and highly
coordinated developmental process that
yields succulent and fl avourful tissues for
organisms that consume and disperse the
associated seed (Giovannoni, 2001). Ripen-
ing involves softening of the fruit tissues to
facilitate seed dispersal. In addition to
softening, fruits normally exhibit increased
accumulation of sugars, acids, pigments
and volatile compounds that increase
interest and palatability to animals.
Additionally, fruits are an important source
of supplementary diet, providing minerals,
vitamins, fi bre and antioxidants for
humans. From an agronomical point of
view, nutritional value, fl avour, processing
qualities and shelf-life determine the
quality of fruit. Additional fruit attributes,
including early maturity, enhanced colour
and increased size, constitute the selection
of so-called domestication traits.
The main changes associated with
ripening include colour (loss of green
colour and increase in non-photosynthetic
pigments that vary depending on species
and cultivar), fi rmness (softening by cell-
wall-degrading activities), taste (increase in
sugar and decline in organic acids) and
fl avour (production of volatile compounds
providing the characteristic aroma).
2.2 Hormonal Control during Ripening
Based on the increase in respiration and
concomitant increase in synthesis of
ethylene during ripening, fl eshy fruits are
classifi ed as either 'climacteric' or 'non-
climacteric'. Ethylene synthesis in climac-
teric fruits such as tomato, apple and
banana is essential for normal fruit
ripening, and blocking either synthesis or
perception prevents ripening. As expected,
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