EFFECTS OF ABIOTIC STRESSES ON CYCLOPHILIN GENE-EXPRESSION IN MAIZE AND BEAN AND SEQUENCE-ANALYSIS OF BEAN CYCLOPHILIN CDNA

In a search for stress-related genes, a differential screening of a mercuric chloride-treated maize cDNA library has been performed. Among the positive clones identified, one, designated as CHEM 7, has been found to be expressed at a significantly higher level in stressed plants than in non-stressed plants. The sequence of CHEM 7 showed complete identity to maize (Zea mays L.) cyclophilin (CyP) described earlier. CHEM 7 was used as a probe to screen a chemically-stressed bean cDNA library. DNA sequencing of the longest positive clone revealed a high homology with maize CyP cDNA. Time course studies of CyP mRNA accumulation upon chemical stress in maize and bean (Phaseolus vulgaris L.) showed that in maize maximum amounts of mRNA are found 6-7 h after treatment, whereas in bean there is a rather long delay before mRNA synthesis is stimulated and the maximum accumulation is only reached 48 h after the onset of stress. Southern blot analysis suggests that maize CyP is encoded by a small family of genes (6-7) but there is only a single CyP gene in bean. CyP mRNA synthesis is not only stimulated by a mercuric chloride treatment but also by other abiotic stresses such as heat-shock, wounding, salt stress and low temperature.