CHANGES IN THE ACCUMULATION OF CYTOSOLIC CYCLOPHILIN TRANSCRIPTS IN CULTURED PERIWINKLE CELLS FOLLOWING HORMONAL AND STRESS TREATMENTS

Cyclophilins (CyPs) are a family of highly conserved proteins that cat alyze cis-trans isomerization of peptidylprolyl bonds and also act as chaperones. In spite of the biological importance of these enzymes, th e regulation of the CyP genes remains poorly known. We found in periwi nkle cell cultures that zeatin, abscisic acid, NaCl, LaCl3, high sucro se concentration and cold stress caused an increase in the accumulatio n of transcripts from a cytosolic CyP gene. By contrast, the expressio n of the che CyP gene was neither heat shock-nor gibberellic acid-resp onsive, whereas hypoxia or presence of phosphates in the medium led to a rapid and severe decrease In the CyP messages. We also examined the pattern of expression of the CyP gene in young periwinkle plants. CyP transcripts accumulated in all organs studied, but in lower amounts i n flower buds than in leaves and roots. From our data, we conclud that : (i) CyP expression is often but not always associated with stress re sponses; (ii) CyP transcript accumulation is independent of cell mitot ic activity; and (iii) there is no correlation between the alkaloid bi osynthesis and the content of CyP messages in the periwinkle cells.