PLANT PHYSIOLOGY , Vol 114, Issue 1 255-263, Copyright © 1997 by American Society of Plant Biologists
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GENE REGULATION AND MOLECULAR GENETICS |
Suppression of Ripening-Associated Gene Expression in Tomato Fruits Subjected to a High CO2 Concentration
C. Rothan, S. Duret, C. Chevalier and P. Raymond
Station de Physiologie Vegetale, Institut National de la Recherche Agronomique BP 81, 33883 Villenave d'Ornon Cedex, France
High concentrations of CO2 block or delay the ripening of fruits. In this
study we investigated the effects of high CO2 on ripening and on the
expression of stress- and ripening-inducible genes in cherry tomato
(Lycopersicon esculentum Mill.) fruit. Mature-green tomato fruits were
submitted to a high CO2 concentration (20%) for 3 d and then transferred to
air. These conditions effectively inhibited ripening-associated color
changes and ethylene production, and reduced the protein content. No
clear-cut effect was observed on the expression of two proteolysis-related
genes, encoding polyubiquitin and ubiquitin-conjugating enzyme E2,
respectively. Exposure of fruit to high CO2 also resulted in the strong
induction of two genes encoding stress-related proteins: a
ripening-regulated heat-shock protein and glutamate decarboxylase.
Induction of these two genes indicated that high CO2 had a stress effect,
most likely through cytosolic acidification. In addition, high CO2 blocked
the accumulation of mRNAs for genes involved in the main ripening-related
changes: ethylene synthesis (1-aminocyclopropane-1-carboxylic acid synthase
and 1-aminocyclopropane-1-carboxylic acid oxidase), color (phytoene
synthase), firmness (polygalacturonase), and sugar accumulation (acid
invertase). The expression of ripening-specific genes was affected by CO2
regardless of whether their induction was ethylene- or
development-dependent. It is proposed that the inhibition of tomato fruit
ripening by high CO2 is due, in part, to the suppression of the expression
of ripening-associated genes, which is probably related to the stress
effect exerted by high CO2.
