The Role Of Glutathione In The Regulation Of Root Artichitecture In Caragana Korshinskii Kom.

Drought stress accompanied with oxidative stress would produce large numbers of reactive oxygen species,breaking the redox balance,to affect the normal activities in plants.Glutathione,an important antioxidant be located at root apical meristem,played an key role in resisting drought stress in plant roots.However,there is little research on how glutathione regulated plant roots to adapt to drought stress.Caragana korshinskii Kom.,distributed in the arid and semi-arid areas of Northwest,is important xerophytes in China,with a strong tolerance to harsh stress.The main reason for its drought tolerance is its developed roots which extended to the deep soil to absorb moisture.However,the mechanism of the developed roots formation in C.Korshinskii under drought stress is still unclear.Present research had selected PEG6000 to simulate drought stress in indoor and investigated the morphological structures,physiological parameters,gene expressions and protein expressions to clarify the mechanism of the developed roots formation in C.Korshinskii under drought stress.The major results as following:(1)Analysing the root growth in different treatments in C.Korshinskii.The results showed that the primary root lengths all are longer than that without any treatments both in the drought-treatments simulated with 5% PEG6000 and the auxin-treatments.The primary root lengths are shorter than that without any treatments in the glutathione synthesis inhibitor treatments.The phenotypes which could be complemented with DTT,a strong reducing agent,are consistent with that treated with the auxin transport inhibitor.These results demonstrated that the reason for the developed root system in C.Korshinskii under drought stress is the interaction between the redox regulation and auxin polarity transport.(2)Detecting glutathione distribution using laser confocal.Analyzing glutathione content and glutathione S-transferase with different treatments in the root tips in C.Korshinskii.The laser confocal results showed that the fluorescence intensity in roottips with drought-stress treatments were the strongest of the three treatments,and the glutathione synthesis inhibitor treatments had the weakest fluorescence intensity.The glutathione content analysis results showed that the glutathione contents markedly increased under drought stress and decreased with glutathione synthesis inhibitor.The activity of glutathione S-transferase elevated under drought stress.The above results indicated that the formation of developed root system in C.korshinskii under drought stress was related to the regulation of glutathione.(3)Using paraffin sections to detect the activity of cell division and proliferation in root tips in C.korshinskii with different treatments.The results suggested that the activity of cell division and proliferation enhanced under drought stress.Correspondence analysis indicated that glutathione regulated root growth through affecting cell division and proliferation in C.korshinskii under drought stress.(4)Detecting the CkPIN1 expression using qRT-PCR and the expression and S-glutathionylation of PIN1 using Western-blotting in leaves and root tips under different treatments in C.Korshinskii.These results showed that S-glutathionylation of PIN1 increased under drought stress to protect PIN1 from ubiquitination degradation,enhancing the expression of PIN1 protein level under drought treatment.Based on the above experimental results,the following conclusion are drawn:The increasing S-glutathionylation of PIN1 protein enhanced the polar transport of auxin and affected the distribution of auxin in root tips,which promoting cell division and proliferation in root apical meristem in C.korshinskii under drought stress.All above is the mechanism of the developed root system in C.Korshinskii under drought stress.