Production of reactive oxygen species and induction of signaling pathways for the ACO gene expressions in tomato plants triggered by the volatile organic compound ether.

Diethyl ether (ether), a volatile organic compound, is widely used as an industrial solvent and easily released to the environment. Acute exposure of tomato plants to high concentrations of ether caused young leaves to curl. Histochemical analyses revealed that superoxide anion (•O(2-) and hydrogen peroxide were formed sequentially by ether, and that (•O(2-) was the major ROS produced in response to ether exposure. We observed cell death by microscopic inspection of Evans blue-stained samples, following fumigation with ether for 6 h. The ethylene biosynthetic gene, 1-aminocyclopropane-1-carboxylic acid oxidase (ACO), was induced as early as 15-30 min after ether fumigation and could be activated at ether concentration as low as 1 µL/L. Induction of ACO gene expression occurred simultaneously with ROS accumulation and coincided with the occurrence of cell death. Simultaneous treatment of tomato plants with mechanical wounding and ether induced differential expression of the ACO gene family. Ether strongly induced ACO4 and moderately induced ACO1, whereas mechanical wounding strongly induced ACO1 and slightly induced ACO4. Induction of the ACO gene family by ether occurred via different signaling pathways. While the ACO1 gene was induced via protein phosphorylation, the ACO4 gene was induced through protein dephosphorylation. Induction of ACO1 and ACO4 might be through MPK1, MPK2, MPK3, and PP2Ac1. These results suggest that the cellular responses of tomato plants to ether are different from the plant responses to ozone, and that tomato plants respond to different air pollutants through different perceptions and downstream signaling pathways.

Extracellular matrix remodeling attenuated after experimental postinfarct left ventricular aneurysm repair.

BACKGROUND: Left ventricular aneurysm repair (LVAR) prevents congestive heart failure after myocardial infarction (MI). LV dilation after MI is related to postinfarct myocardial remodeling and leads to CHF. Because changes in matrix metalloproteinases (MMPs), tissue inhibitors of metalloproteinases (TIMPs), and the physical properties of collagens are involved in myocardial remodeling, the effect of postinfarct LVAR on these factors was tested. METHODS: Rats with surgically induced MI, which did or did not receive postinfarct LVAR, were compared with each other and with controls. TIMP messenger RNA and protein expression, MMP gelatin zymography activity, and collagen fibrosis were measured in heart tissue. RESULTS: A threefold difference in the infarction area ratio was observed between samples of LVAs and of repaired LVAs. Compared with rats without LVAR, rats with repaired LVAs exhibited a higher percentage fractional shortening and significantly lower LV end-systolic and end-diastolic diameters. These salutary effects on LV diameter after LVAR were accompanied by a reversal of myocardial remodeling activity. After MI, TIMP expression decreased, MMP activity increased, and collagen fibrosis increased. After LVAR, TIMP expression increased, and MMP activity and collagen fibrosis decreased. These markers of remodeling activity changed significantly and approached preinfarct levels after LVAR. CONCLUSIONS: This study demonstrated that postinfarct LVAR prevents further congestive heart failure by attenuating myocardial remodeling in the LV and is thus indicated both to prevent heart failure and to reduce excessive postinfarct myocardial remodeling.