IDENTIFICATION AND IMMUNOLOCALIZATION OF A 65 KDA DROUGHT-INDUCED PROTEIN IN CULTIVATED TOMATO LYCOPERSICON-ESCULENTUM

A 65 kDa protein with a pI value of 5.2 accumulated gradually in tomato leaves during water stress. Protein levels returned to those of the control upon rehydration of the plants. Antiserum raised against the protein, purified from two dimensional electrophoresis gels, was obtained and used as a probe to localize the protein in tomato leaves by immunofluorescence and immunogold labeling. The protein was found to be mainly localized in different areas of nuclei (peripheral chromatin masses, nucleoli and nucleoplasm), chloroplasts, and some leaf cell cytoplasmic regions. Quantification of the gold labeling clearly demonstrated that the amount of the protein increased significantly in nuclei and chloroplasts of cells in drought-stressed plants. Cytological changes occurring in leaf tissues during water stress are also reported.