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 the assembly of carotenoid-containing fibrils and was also found to accumulate 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, drought, 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 apparently more sensitive to photo-oxidative stress than tomato. Similarly, wounding which causes strong induction of the promoter in tobacco, produces only weak induction in tomato. Hydrogen peroxide produced in plastids or added exogenously causes the induction of this nuclear gene. Our data suggest that the ascorbate/glutathione pathway (which eliminates hydrogen peroxide) can influence indirectly the induction of the fibrillin promoter. We propose a generalized model which links stresses of external origin to nuclear gene induction, via the plastid compartment which is subjected to photo-oxidative stress.
Manac'h
N
Génétique moléculaire des plantes, CNRS/UMR 5575, université Joseph-Fourier, BP53, 38041 Grenoble cedex 9, France.
Kuntz
M