Physiological Mechanisms Of Oxytetracycline On Growth And Cell Division Of Tomato Root

The deteriorating of soil organic pollution is serious restricting the sustainable development of agriculture in our country. Recent years, with the rapid development of intensive livestock industry, the antibiotics pollution caused by overuse of organic fertilizer in agro-ecosystems is becoming more and more serious, and results in severe harm to the yield and quality of crops. However there is fewer studies on the effects of soil antibiotics pollution on plant growth and development, and the mechanisms remain to be further examined. In this study, we use tomato root as plant material to elucidate the effects of Oxytetracycline on the growth of tomato root. What’s more, we preliminary discussed the inhibition mechanism of Oxytetracycline in cell division of tomato root tip. The main results are as follows:1. We have noticed that the growth and cell division of tomato root were suppressed significantly by Oxytetracycline. We found that the growth of taproot was suppressed significantly, the root tip meristem length reduced significantly, the cell proliferation index (Pi) and S-phase cell fraction (SPF) dramatically declined, the cell cycle related genes expression were significantly down-regulated after 10μM Oxytetracycline treatment. What’s more, the Arabidopsis DNA damage related mutants atm、atr、wee1 and sog1 were not sensitive to Oxytetracycline treatment. These results suggest that the effects of Oxytetracycline treatment on growth and cell division of tomato root were not caused by DNA damage.2. We have found that the inhibitory effect of Oxytetracycline on the growth and cell division of tomato root were related to the reducing of reactive oxygen species accumulation in tomato root. We found that the accumulation of reactive oxygen species reduced gradually during Oxytetracycline treatment. The phenotype and ROS staining results of DPI, an inhibitor of NADPH oxidase, were similar to the Oxytetracycline treatment, and there was no superimposed effect of Oxytetracycline and DPI treatment on the growth of tomato root. Under stress conditions of oxytetracycline, we added 1 mM hydrogen peroxide and found that the accumulation of ROS, the root length, the meristem length, the cell proliferation index (Pi) and S-phase cell fraction (SPF), the cell cycle related genes expression increased significantly. These results suggest that the inhibitory effect of Oxytetracycline on the growth and cell division of tomato root were related to the reducing of reactive oxygen species accumulation in tomato root, and exogenous hydrogen peroxide can obviously alleviate the inhibitory effect of Oxytetracycline.3. We have demonstrated that Oxytetracycline suppressed the growth and cell division of tomato root by increasing the accumulation of nitric oxide in tomato root. We noticed that the accumulation of nitric oxide increased significantly in tomato root after 10 μM Oxytetracycline treatment; the application of sodium tungstate, an inhibitor of nitrate reductase, can obviously alleviate the inhibitory effect of Oxytetracycline; the application of cPTIO, the NO scavenger, can rescue the suppression of Oxytetracycline on tomato root and promote the cell cycle related genes expression, indicating that Oxytetracycline suppressed the growth and cell division of tomato root by increasing the accumulation of nitric oxide mediated by nitrate reductase. Furthermore, the accumulation of ROS was affected by cPTIO treatment, indicating that the interaction of ROS and nitric oxide plays an important role in regulating the growth and cell division of tomato root under stress conditions of oxytetracycline.