Proline synthesis and degradation: a model system for elucidating stress-related signal transduction

genes such as RD29A, KIN2, and RAB18 are reviewed. Further analysis of the factors that induce these genes A causal relationship between increased proline synmay assist in elucidating the mechanisms involved in thesis and plant tolerance of hyperosmotic stresses stress-induced proline accumulation. Putative stresshas been demonstrated. Nonetheless, the molecular regulated promoter elements in the AtP5CS1, AtP5CS2 basis of this effect is not yet established. Proline accuand AtP5CR genes are identified. Recent evidence that mulation appears to be mediated by both ABA-dependa signal related to proline synthesis and/or degradaent and ABA-independent signalling pathways, tion selectively increases the expression of stressalthough the events that occur between the perception related genes underscores the importance of elucidatof stress and the induction of proline biosynthetic ing the signalling events associated with proline accugenes are poorly characterized. Recent evidence supmulation under adverse conditions. ports an important role for post-transcriptional events in dehydrationand ABA-induced proline synthesis.