de la structure à la croissance cellulaire - Université Bordeaux 1

102 M. Bourdon et al.
their importance in human nutrition and their economic inference, fleshy fruit
species have been the subject of developmental studies, mostly devoted to ovary
formation, fruit set, and fruit maturation. The growth phase of the fruit has been
much less addressed, although the complex interplay between cell division and cell
expansion during this period is a crucial determinant of the final size, weight and
shape of fruits. This chapter aims at reviewing our current knowledge on fleshy fruit
development and addresses the cellular and molecular mechanisms involved in
their growth, with a special emphasis on the cell expansion associated process of
endoreduplication, with tomato fruit as the model species for fleshy fruits.
1 Introduction
The fruit is a plant organ specific to Angiosperms, which typically contains the
seeds. At the botanical level, most fruits develop from mature ovaries and, therefore,
include carpel tissues in part or whole. Additionally, many species develop
mature fruit tissues from extracarpellary floral components, e.g., strawberry, pineapple,
mulberry, and pome fruits (apple, pear), in which the receptacle, bracts,
calyx, and floral tube (the fused base of floral organs), respectively constitute the
majority of mature fruit tissue (Coombe 1976; Gillaspy et al. 1993; Nitsch 1953).
The fruit has evolved in Angiosperms to fulfill ovule and seed protection during
embryo development, and seed dispersal after maturation. This important physiological
function accounts for a significant part of the adaptive success of Angiosperms.
As such, the fruit has been under strong selective pressure, which accounts
for the very wide diversity of fruit size, form and composition, and of seed and fruit
dispersion mechanisms. These mechanisms range from the small, nondehiscent
akene dry fruit, dispersed by wind, to the large, fleshy, and juicy berry and drupe
fruits, which have to be eaten by animals, such as mammals or birds for seed
dispersion and germination. As an example, the Solanaceae family, which encompasses
nearly 10,000 species, has very diverse types of fruits, with capsules, drupes,
pyrenes, berries, and several sorts of dehiscent noncapsular fruits occurring in more
than 90 genera (Knapp 2002).
According to common use, fruit refers to the fleshy, edible fruits, such as grape,
banana, tomato, citrus, cucurbits, pomes, stone fruit, and mango. These species are
subjected to major agricultural production, which rely on permanent selection and
improvement in yield and quality. Their common feature is tissues that accumulate
water and many organic compounds, such as sugars, organic acids, pigments, flavor
and aromas, and vitamins, which bestow their juiciness and attractiveness. Most
fundamental knowledge exists about the control of maturation of fleshy fruit
(Giovannoni 2001, 2004), and their postharvest handling (Brecht et al. 2003;
Soliva-Fortuny and Martin-Belloso 2003), and more recently, about the processes
involved in carpel morphogenesis and fruit set by using the model dry fruit of