Protection of Sinorhizobium against Host Cysteine-Rich Antimicrobial Peptides Is Critical for Symbiosis

A bacterial membrane protein, BacA, protects Sinorhizobium meliloti against the antimicrobial activity of host peptides, enabling the peptides to induce bacterial persistence rather than bacterial death

Developmental and environmental regulation of the Nicotiana plumbaginifolia cytosolic Cu/Zn-superoxide dismutase promoter in transgenic tobacco.

Superoxide dismutases (SODs) play a key role in the cellular defense against reactive oxygen species. To study the transcriptional regulation at the cellular level, the promoter of the Nicotiana plumbaginifolia cytosolic gene encoding Cu/ZnSOD (SODCc) was fused to the beta-glucuronidase (GUS) reporter gene (gusA) and analyzed in transgenic tobacco plants. The promoter was highly active in vascular bundles of leaves and stems, where it is confined to phloem cells. In flowers, GUS activity was detected in ovules and pollen grains, in pigmented tissues of petals, and in vascular tissue of ovaries and anthers. In response to treatment with the superoxide-generating herbicide paraquat, very strong GUS staining was observed in photosynthetically active cells of leaves and in some epidermal root cells of seedlings. The expression of the SODCc-gusA was also induced in seedlings after heat shock and chilling and after treatment with sulfhydryl antioxidants such as reduced glutathione and cysteine. It is postulated that SODCc expression is directly linked to a cell-specific production of excess superoxide radicals in the cytosol

Differential regulation of superoxide dismutases in plants exposed to environmental stress.

Superoxide dismutases (SODs) are metalloproteins that catalyze the dismutation of superoxide radicals to hydrogen peroxide and oxygen. The enzyme is ubiquitous in aerobic organisms where it plays a major role in defense against oxygen radical-mediated toxicity. In plants, environmental adversity often leads to the increased generation of reduced oxygen species and, consequently, SOD has been proposed to be important in plant stress tolerance. Here we describe the isolation of a cDNA clone encoding a cytosolic copper/zinc SOD from Nicotiana plumbaginifolia. Using this, together with previously isolated cDNAs encoding the mitochondrial manganese SOD and the chloroplastic iron SOD as probes in RNA gel blot analyses, we have studied SOD transcript abundance during different stress conditions: in response to light, during photoinhibitory conditions (light combined with high or low temperatures), and in response to a xenobiotic stress imposed by the herbicide paraquat. Evidence is presented that iron SOD mRNA abundance increases whenever there is a chloroplast-localized oxidative stress, similar to the previous finding that manganese SOD responds to mitochondria-localized events. The diverse effects of the different stress conditions on SOD mRNA abundance thus might provide an insight into the way that each treatment affects the different subcellular compartments