Expression and molecular cloning of drought-induced genes in the wild tomato Lycopersicon chilense.

Protein synthesis and translatable mRNA population changes induced during water stress were studied in leaves of a drought-resistant wild relative of tomato, Lycopersicon chilense, using one- and two-dimensional polyacrylamide gel electrophoresis. Under our experimental conditions, water deficit did not significantly affect total protein synthesis capacity. However, it induced biphasic synthesis of a new set of proteins. These newly synthesized proteins resumed to control levels upon rehydration of the plants. Certain drought-induced proteins also accumulated in leaves subjected to heat shock (39 degrees C) or exogenous abscisic acid (ABA, 1 mM) treatments. A cDNA library was constructed using poly(A)+ RNA from leaves of plants exposed to drought stress for 4 days. Differential screening of the library identified three groups of clones corresponding to drought- and ABA-induced mRNAs. Northern blot analysis showed that the genes of selected clones respond differently to the different environmental stresses. Our data clearly demonstrate that water stress alters gene expression in L. chilense plants resulting in the synthesis of new proteins, of which several respond to high temperature stress and others to an osmotic effect. These responses are in part modulated by ABA.