BEAN CYCLOPHILIN GENE-EXPRESSION DURING PLANT DEVELOPMENT AND STRESS CONDITIONS

Cyclophilins (Cyp) are ubiquitous proteins with peptidyl-prolyl cis-tr ans isomerase activity that catalyses rotation of X-Pro peptide bonds and facilitates the folding of proteins; these enzymes are believed to play a role in in vivo protein folding. During development of normal bean plants, Cyp transcripts are first detected three days after begin ning of germination and are present in all plant tissues examined. In a general way, higher amounts of Cyp mRNAs are found in developing tis sues. Cyp mRNA accumulates in alfalfa mosaic virus-infected bean leave s and after ethephon and salicylic acid treatments. In response to a l ocalized chemical treatment Cyp mRNA accumulation is observed in the u ntreated parts of the plants; however these changes in mRNA levels are restricted to the aerial part of the plant. A comparative study of Cy p mRNA accumulation in bean and maize in response to various external stimuli shows striking differences in profiles between the two plants. For instance, in response to heat shock, maize Cyp mRNA significantly accumulates, whereas no remaining mRNA is observed a few hours after the beginning of the heat stress in bean. Differences in mRNA accumula tion profiles are also observed upon salt stress which induces the res ponse earlier in maize than in bean, whereas the opposite situation is observed when plants are cold-stressed. All these findings further su ggest that cyclophilin might be a stress-related protein.