Stress induction of a nuclear gene encoding for a plastid protein is mediated by photo-oxidative events

Fibrillin was originally identified as a chromoplast protein involved in th e assembly of carotenoid-containing fibrils and was also found to accumulat e in chloroplasts of wounded or water-stressed leaves. We now show that the promoter from the pepper fibrillin (nuclear) gene can be induced in leaves of stable tomato transformants by various stresses, namely wounding, droug ht, cold and salt stress, in light but not in darkness, as well as by high light intensities. Various herbicides causing reactive oxygen (superoxide, singlet oxygen) production in chloroplasts also induce the promoter. Higher expression levels are observed in transgenic tobacco plants which are appa rently mon sensitive to photo-oxidative stress than tomato. Similarly, woun ding which causes strong induction of the promoter in tobacco, produces onl y weak induction in tomato. Hydrogen peroxide produced in plastids or added exogenously causes the induction of this nuclear gene. Our data suggest th at the ascorbate/glutathione pathway (which eliminates hydrogen peroxide) c an influence indirectly the induction of the fibrillin promoter. We propose a generalized model which links stresses of external origin to nuclear gen e induction, via the plastid compartment which is subjected to photo-oxidat ive stress. (C) 1999 Editions scientifiques et medicales Elsevier SAS.