Effects of abiotic stresses on cyclophilin gene expression in maize and bean and sequence analysis of bean cyclophilin cDNA

Abstract

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.