DESICCATION LEADS TO THE RAPID ACCUMULATION OF BOTH CYTOSOLIC AND CHLOROPLASTIC PROTEINS IN THE RESURRECTION PLANT CRATEROSTIGMA-PLANTAGINEUM HOCHST

A number of desiccation-related and abscisic-acid (ABA)-inducible transcripts have been isolated from the resurrection plant Craterostigma plantagineum (Scrophulariaceae). They have been analysed at the transcriptional level (D. Bartels et al., 1990, Planta 181, 27-34) and their nucleotide sequences determined (D. Piatkowski et al., 1990, Plant Physiol. 94, 1682-1688). Three such genes encoded polypeptides with substantial homologies to proteins abundantly expressed during late embryogenesis in many higher plants; two other genes encoded novel transcripts. The temporal expression patterns of these gene products and their distribution in different organs of the plant and in callus tissues have now been analysed immunologically. For this, in-situ RNA hybridizations and immunocytochemical studies using tissue sections were carried out at both the light and electron microscope level. All of the products were found to be present in leaf tissue, and some were also found in roots and in seeds. Three desiccation-related proteins were localized in the cytosol, while two others, one associated with the thylakoid membranes, the other soluble in the stroma, were detected in the chloroplast. In C. plantagineum the severe ultrastructural changes observed during the desiccation-rehydration process indicate the need for protectants: the gene products characterized in this publication may be good candidates for this role.