Metablites Of Endophytic Fungi From Ginkgo Biloba And Their Bioactivity In Increasing Tolenrance To Chilling Injury Of Wheat Seedlings

Co-evoluting with host plants, endophytic fungi play an important ecological role in growth and resistance process of host plants due that they can metabolize large amounts of substances with various biological activities including antibacterial, insecticidal and plant growth regulation and other important activities. In our study,80strains from Ginkgo biloba L. were obtained and priliminarily classified based on morphological characters. Cerebrosides-producing strain TP78(Phyllosticta sp., GenBank:KC445736) were selected using chemical method of1H-NMR and studied subsequently. By solid-state fermentation, cerebroside B and cerebroside C were yieleded from the crude extracts of TP78. We also study the promotion and mechanism of cerebroside C on increasing tolenrance of wheat seedlings (Triticum aestivum cv. Huaimai25) under low temperature.Researching in promoting of cerebroside C (CC) on seed germination showed that CC improved seed germination at different concentration (5,10,20,50μg/mL) under cold stress. The results also demonstrated that CC treatments at20μg/mL expressed the highest germination rate (77.80%), potential (23.46%), index (18.51) and the shortest germination time (7.08d), displaying significant differences between CC-treatments and the control groups.After comparing the different effects of CC between at4℃stress and25℃on the seedlings growth through mansuatting root length, shoot height and their fresh/dry weight, results were discovered as follows:(1) CC had few effects on neither shoots or roots of wheat seedlings at room temperature but promoted root growth and increased dry substance accumulation in roots under cold stress;(2) CC had a major role in root growth and dry matter accumulation in roots of wheat seedlings;(3) CC enhanced the enzyme activity of catalase (CAT) and decreased the content of lipid peroxide malondialdehyde (MDA) in roots, with few effects on the indicators in shoots.Researching on the changes in physiological and biochemical characteristics in roots of wheat showed that (1) cerebroside C decreased membrane relative permeability (RMP) and inhibited accumulation of MDA in root to prevent intracellular protective materials from extravasating;(2) CC inhibited the activities of lipoxygenase (LOX), phospholpase C (PLC), phospholpase D (PLD), which are on behalf of disassembling phospholipid and unsaturated fatty acid to maintain the structural integrity and functional stability of cell membrane;(3) CC induced accumulations of unsaturated fatty acids to increase the degree of unsaturated fatty acids, thereby reducing the phase transition temperature of membrane and alleviating membrane damage;(4) CC increased the activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) in roots, protecting cell membrane from oxidative damage;(5) CC promoted the accumulation of intracellular substances soluble sugar and soluble protein in roots, thus increasing membrane osmotic adjustment ability.In summary, the metabolite of cerebroside C isolated from the endophytic Phyllosticta sp.(TP78) in gikgo biloba could increase tolenrance to chilling injury of wheat seedlings through maintaining the structural integrity and functional stability of root membrane.