Study On The Physiological And Biochemical Response And Differentially Expressed Proteome Under Cold Stress In Buffalograss

Buffalograss is a kind of gramineae warm-season turfgrass. It originated in the Western North American prairie. Since the 1950s, buffalograss has been introducted to Beijing. Now it is an important turf grass for green environment, water and soil conservation. Compared to cool-season turfgrass and other warm-season turfgrass, buffalograss tends to have a more better characteristics, for example, less water and fertilizer requirement, without frequent trimming, drought-resistance, disease-resistance, very low maintenance costs and less environmental pollution etc. So it is an ideal "water-saving and environmental protection" turfgrass. But one of prominent drawbacks of buffalograss is that life cycle is very short and cold intolerance. Therefore the application of buffalograss is limited in the majority of China's northern region. The study will provided new insights into low temeperature stress responses and theoretical guidance for research of cold-resistance mechanism in buffalograss. At present, the study on the adjustment mechanism of cold resistance was not reported.In this study, by applying technology of plant physiology and biochemistry, combined with proteomics technology we analyzed effect of the low temperature stress on the physiological and biochemical responses on 4 week-old buffalograss treated at 5℃for 6 h and 24 h, and carried out the analysis of differential proteomics on leaf total protein under 5℃for 24 h. The aim of this study is to explore the mechanism of cold resistance on buffalograss.The results are as follows:(1) The leaf cell membrane of buffalograss seedlings subjected to a certain degree of damage under low-temperature stress. And the longer the stress time is, the greater the damage, the greater the relative conductivity. Under a certain stress, leaf cell membrane of buffalograss would not cause permanent damage. Meanwhile root vitality of buffalograss seedlings was affected largely by low temperature. The root vitality decreased quickly under cold stress. This demonstrated the root system was important to maintain normal growth and development of plants, and it was looked upon as an important indicator for identification of cold tolerance of plants.(2) With the extension of the stress time, SOD, POD and CAT activity in buffalograss leaves increased at the early of low temeperature stress and decreased at end. Under the 6 h stress, SOD activity had been to maintain a high level, POD activity showed a greater change. When the stress lasted until 24 h, POD activity decreased and almost flatted compared with the control, this showed that POD activity was sensitive under the low temperature stress. Changes of CAT and SOD activity were in the line, the results indicated that activity of two enzymes coordinated the regulation of low-temperature adaptation.(3) Osmotic regulation substances closely related to the low temperature adjustment mechanism of buffalograss seedlings. Under low temperature stress, soluble sugar content would increase along with the stress time. Low temperature induced changes in the soluble protein content in buffalograss leaves, this result displayed that soluble protein played an important role in the protection of cell under the low temperature stress. Change of proline content was sensitive under low temepertaure stress, and proline content would sharply increase in the early, with the extension of stress time, proline content slowly decreased again. However, proline content remained at a relatively high level throughout the course of cold stress. Results showed proline was an important regulator in low-temperature regulation mechanism.(4) In this experiment, we analyzed the changes of differential proteins in buffalograss leaves under 5℃for 24 h. An optimized protocol was developed paying special attention to the analyses of leaf total protein on buffalograss based on 2-DE. The optimization included sample preparation, electrophoresis conditions etc. It is a very important platform to study proteome of buffalograss. The finally 2-DE results showed that under low-temperature stress, a total of 51 protein spots were detected, whose expression changed at least at 2-fold. Among them, 7 protein spots were down-regulated, 31 were up-regulated, 1 protein spot expressed in control then didn't in treat and 12 spots exoressed in treat then didn't in control. MALDI-TOF-MS analysis allowed the identification of 8 differentially expressed proteins from the 13 selected points. Of these 8 proteins, three proteins were relevant to energy metabolism, one is an important enzyme in fatty acid metabolism, one involved in signal transduction,and other three were identification undecided protein and hypothesis protein. The results indicated that these proteins were involved in many metabolic processes.