PLANT PHYSIOLOGY , Vol 110, Issue 4 1207-1214, Copyright © 1996 by American Society of Plant Biologists
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WHOLE PLANT, ENVIRONMENTAL, AND STRESS PHYSIOLOGY |
Reversible Inhibition of Tomato Fruit Gene Expression at High Temperature (Effects on Tomato Fruit Ripening)
S. Lurie, A. Handros, E. Fallik and R. Shapira
Department of Postharvest Science, Agricultural Research Organization, The Volcani Center, Bet Dagan 50250 Israel (S.L., A.H., E.F.)
The reversible inhibition of three ripening-related processes by
high-temperature treatment (38[deg]C) was examined in tomato (Lycopersicon
esculentum L. cv Daniella) fruit. Ethylene production, color development,
and softening were inhibited during heating and recovered afterward,
whether recovery took place at 20[deg]C or fruit were first held at
chilling temperature (2[deg]C) after heating and then placed at 20[deg]C.
Ethylene production and color development proceeded normally in heated
fruit after 14 d of chilling, whereas the unheated fruit had delayed
ethylene production and uneven color development. Levels of mRNA for
1-aminocyclopropane-1-carboxylic acid oxidase, phytoene synthase, and
polygalacturonase decreased dramatically during the heat treatment but
recovered afterward, whereas the mRNA for HSP17 increased during the
high-temperature treatment and then decreased when fruit were removed from
heat. As monitored by western blots, the HSP17 protein disappeared from
fruit tissue after 3 d at 20[deg]C but remained when fruit were held at
2[deg]C. The persistence of heat-shock proteins at low temperature may be
relevant to the protection against chilling injury provided by the heat
treatment. Protein levels of 1-aminocyclopropane-1-carboxylic acid oxidase
and polygalacturonase also did not closely follow the changes in their
respective mRNAs. This implied both differences in relative stability and
turnover rates of mRNA compared to protein and nontranslation of the
message that accumulated in low temperature. The results suggest that high
temperature inhibits ripening by inhibiting the accumulation of
ripening-related mRNAs. Ripening processes that depend on continuous
protein synthesis including ethylene production, lycopene accumulation, and
cell-wall dissolution are thereby diminished.
