Cellular, Metabolic and Molecular Aspects of Chromoplast Differentiation in Ripening Fruit - Fruit Ripening: Physiology, Signalling and Genomics - page 28

3 Cellular, Metabolic and Molecular
Aspects of Chromoplast Differentiation in
Ripening Fruit

Jean Claude Pech, 1,2 * Mondher Bouzayen 1,2 and Alain Latché 1,2
1 Université de Toulouse, Castanet-Tolosan, France; 2 INRA, Castanet-
Tolosan, France

3.1 Introduction

of large starch grains, respectively.
Whatever the origin of the chromoplast, the
common feature is the accumulation of
carotenoids due to the upregulation of
carotenoid biosynthesis genes. In a few
cases, such as the rind of cantaloupe
melons, similar to senescent leaves, the
yellowing is due to the unmasking of
carotenoids as a consequence of
chlorophyll degradation rather than to the
new synthesis of yellow pigments (Flores
et al. , 2001). In this situation, the yellow
plastids generated from chloroplasts cor-
respond to a senescence-specifi c form of
plastids named gerontoplasts that cannot
be considered as true chromoplasts. In
contrast to all the other forms of plastids,
the metabolism of gerontoplasts is solely
catabolic (Matile et al. , 1999).
The cell biology of chromoplasts started
to be elucidated with electron microscopy
descriptions of their ultrastructure. Various
types of chromoplast have been categorized,
mainly as a function of the structure of
pigment-containing bodies (Ljubesic et al. ,
1991; Camara et al. , 1995). Because most of
the pigments present in chromoplasts are
carotenoids, the carotenoid biosynthesis

Chromoplasts are non-green plastids that
are responsible for the yellow, orange and
red colours of many fruit. They evolve
during fruit ripening by differentiation of
other forms of plastids. In a number of
fruit, such as tomatoes and peppers,
coloured chromoplasts are derived from
green chloroplasts with the disintegration
of the thylakoid membranes and the
formation of new carotenoid-bearing
structures (Frey-Wyssling and Kreutzer,
1958; Rosso, 1968). In other fruit, such
as the fl esh of developing papayas,
chromoplasts evolve from leuco- or
proplastids, as no intermediate amyloplast
or chloroplast structures are encountered
(Schweiggert et al. , 2011). A very complex
origin of chromoplasts has been found in
mango where a dynamic interconversion of
plastids occurs, although it was not
possible to establish a sequential pattern
(Vasquez-Caicedo et al. , 2006). In this fruit,
a chloroplastic, pro-plastidial and
amyloplastic origin is suspected due to the
persistence of stroma thylakoid structures,
of pro-plastid-like prolamellar bodies and