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.

Yam storage protein dioscorins from Dioscorea alata and Dioscorea japonica exhibit distinct immunomodulatory activities in mice.

The aim of this study was to elucidate the effect of the major storage protein dioscorin isolated from two different yam species, Tainong No. 1 (TN1-dioscorins) and Japanese yam (Dj-dioscorins), on the immune activities of mice. Dj-dioscorins, like TN1-dioscorins, could induce expression of the pro-inflammatory cytokines and stimulate phagocytosis of RAW 264.7. Intraperitoneal injection of the TN1-dioscorins into mice stimulated phagocytosis of bone marrow, spleen, and thymic cells. In contrast, the T and B cells in bone marrow, spleen, and thymus isolated from mice injected with Dj-dioscorins had higher proliferative responses to mitogens. Furthermore, Dj-dioscorins enhanced proliferation of CD4(+), CD8(+), and Tim3(+) (Th1) cells in spleen and CD19(+) cells in both spleen and thymus. Supplement of Dj-dioscorins in the lymphoid cells isolated from Dj-dioscorins primed mice induced cell proliferation of both spleen and thymic cells. These findings indicated that TN1-dioscorins have a higher ability to stimulate the phagocytic activity of the lymphoid cells than Dj-dioscorins, whereas Dj-dioscorins possess more abilities than TN1-dioscorins to enhance the proliferation of the lymphoid cells.