Accumulation of plastid lipid-associated proteins (fibrillin/CDSP34) upon oxidative stress, ageing and biotic stress in Solanaceae and in response to drought in other species.

Plastid lipid-associated proteins, also termed fibrillin/CDSP34 proteins, are known to accumulate in fibrillar-type chromoplasts such as those of ripening pepper fruit, and in leaf chloroplasts from Solanaceae plants under abiotic stress conditions. It is shown here that treatments generating active oxygen species (high light combined with low temperature, gamma irradiation or methyl viologen treatment) result in potato CDSP34 gene induction and protein accumulation in leaves. Using transgenic tomato plants containing the pepper fibrillin promoter, a significant increase in promoter activity in leaves subjected to biotic stress, namely bacterial infections, was observed. In WT, a higher level of the endogenous fibrillin/CDSP34 protein is also observed after infection by E. chrysanthemi strain 3739. In addition to stress-related induction, a progressive increase in the fibrillin promoter activity is noticed during ageing in various tomato photosynthetic tissues and this increase correlates with a higher abundance of the endogenous protein in WT leaves. It is proposed that a mechanism related to oxidative events plays an essential role in the regulation of fibrillin/CDSP34 genes during stress and also during development. Using a biolistic transient expression assay, the pepper fibrillin promoter is found to be active in various dicot species, but not in monocots. Further, substantially increased levels of fibrillin/ CDSP34 proteins are shown in various dicotyledonous and monocotyledonous plants in response to water deficit.

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.

Haloanaerobacter salinarius sp. nov., a novel halophilic fermentative bacterium that reduces glycine-betaine to trimethylamine with hydrogen or serine as electron donors; emendation of the genus Haloanaerobacter.

A novel halophilic fermentative bacterium has been isolated from the black sediment below a gypsum crust and a microbial mat in hypersaline ponds of Mediterranean salterns. Morphologically, physiologically and genetically this organism belongs to the genus Haloanaerobacter. Haloanaerobacter strain SG 3903T (T = type strain) is composed of non-sporulating long flexible rods with peritrichous flagella, able to grow in the salinity range of 5-30% NaCl, with an optimum at 14-15%. The strain grows by fermenting carbohydrates or by using the Stickland reaction with either serine or H2 as electron donors and glycine-betaine as acceptor, which is reduced to trimethylamine. The two species described so far in the genus Haloanaerobacter are not capable of Stickland reaction with glycine-betaine + serine; however, Haloanaerobacter chitinovorans can use glycine-betaine with H2 as electron donor. Strain SG 3903T thus represents the first described strain in the genus Haloanaerobacter capable of the Stickland reaction with two amino acids. Although strain SG 3903T showed 67% DNA-DNA relatedness to H. chitinovorans, it is physiologically sufficiently different from the two described species to be considered as a new species which has been named Haloanaerobacter salinarius sp. nov.