Preliminary Illustrate The Physiological And Molecular Mechanism Of Affecting Arabidopsis Thaliana Primary Root Growth Under Manganese Toxicity

The metal manganese(Mn) is an essential microelement required for normal plant growth and development. It is mainly absorbed by plants in the form of Mn2+.Although Mn plays a very important role, is highly toxic when in excess. The root is the first plant organ to get in contact with the toxin manganese(Mn), Mn inhibits the growth of the primary root. However, the mechanism underlying Mn-mediated modulation of the root system architecture remains unclear. In our research we used physiology method, pharmacology method, genetics method, molecular biology method and so on, then we give following results:1. Mn inhibits the growth of the primary root, further detailed examination resulted from a reduced meristematic cell division potential.2. Auxin homeostasis is involved in plant development and environmental responses and modulated by its biosynthesis, distribution and polar transport.Following Mn exposure, a decrease in auxin levels is associated with reduced PIN protein accumulation, but not with reduced PIN transcript levels. Additionally, Mn stabilized Aux/IAA protein to repress auxin signalling in this Mn-mediated process.3. In addition to the regulation of plant hormones, nitric oxide(NO) is also an important signal molecule for root growth and response for environmental stress.Based on the fluorescence intensity of NO quantitative analysis, as well as verification from pharmacology, genetics and other method. It is proved that the root of NO excessive accumulation is a result of Mn toxicity and inhibition of root growth is one of the reasons.4. In addition, when NO was reduced or eliminated in the root, the fluorescence intensity of DR5rev:: GFP of the auxin dependent transgenic lines showed that the activity of auxin was affected by the NO signal. This result suggests that Mn toxicity induced NO signal increases which ultimately affects the response or content of auxin, may be another reason caused inhibition of root growth.In summary, our results indicate that Mn modulates root growth via the NO-mediated auxin response pathway in Arabidopsis, then affect growth and development of plant.In this paper, we preliminary illustrates the NO signal and auxin are involved in regulating signal pathways and molecular mechanism of Mn toxicity. These studies are helpful for us to further clarify the signaling pathways Mn induced in plant root system, and provide the basis for further illuminating the physiological and molecular mechanism of plant root development under toxicity.