Preliminary Study On Effects And Mechanisms Of Salt And Drought Resistance And Heavy Metals In Nicotiana Tobacum Conferred By Piriformospora Indica

Piriformospora indica was separated from the shrub roots in the Indian desert by Verma in1998for the first time. Similar to Arbuscular Mycorrhizal Fungi(AMF), this fungus promotes plant growth, increases resistance of colonized plants against fungal pathogens and tolerance to abiotic stress. In contrast to AMF P. indica can grow axenically on different synthetic media.Tobacco (Nicotiana tobacum L.) is one of the mold plants, one of the most important economic crops, from seed, seedling to the adult stage and the modulation have received various biotic and abiotic stress, including pest, salt damage, drought and heavy metals and so on. The thesis is mainly about the preliminary study on effects and mechanisms of salt and drought resistance and heavy metals in Nicotiana tobacum conferred by Piriformospora indica. The salient findings of the research are:1、Salt tolerance in Nicobiana tobacum conferred by Piriformospora indicaWe compared the malondialdehyde (MDA) content, Proline (Pro) content, the relative conductance and salt-related genes expression level of P.indica-colonized and un-colonized N. tobacum plants after treated with300mmol/L NaCl. The results showed that P.indica can improve the slat tolerance of N. tobacum. We also analysis the MDA concentration, relative conductance, proline and the relative expression of salt stress-related genes in N.tobacum leaves colonized and un-colonized by P. indica. The result showed that MDA concentration and relative conductance were significantly lower in inoculated plants compared with the uninoculated ones. And the Proline content in P. indica colonized N. tobacum leaves was significantly higher than that in un-colonized ones. RT-PCR analysis showed that the expression of salt tolerance gene OPBP1and pathogenesis-related protein genes PR-1a, PR2, PR3and PR5were upregulated in both P. indica colonized and un-colonized N. tobacum leaves, and the expression of these genes in P. indica colonized N. tobacum was much higher than that un-colonized ones, the result showed that P. indica can enhance the expression level of salt-related genes of N. tobacum. This study indicated that the salt resistance improvement in P. indica colonized N. tobacum was associated with malondialdehyde and proline contents, plasmamembrane permeability, the expression level of salt tolerance genes and pathogenesis-related protein genes. P. indica confer N. tobacum salt tolerance via maintaining cell biomembrane system stability, balancing cell osmotic pressure, and reducing the level of membrane lipid peroxidation of plants.2、 Drought resistance in Nicobiana tobacum conferred by Piriformospora indicIn order to confirm the influence of P. indica on drought tolerance of Nicobiana tobacum,20%polyethylene glycol6000(PEG) was used to stimulate drought conditions to study the mechanisms of drought resistance in Nicobiana tobacum conferred by P. indica. In a pot culture experiment, it showed that P. indica can confer Nicobiana tobacum drought resistance and the differences of malondialdehyde (MDA) and proline contents, the relative conductance and the expression level of drought-related genes between N. tobacum colonized and un-colonized by P. indica were analyzed after PEG treatment. The results showed that the concentration of MDA and the relative conductance in the leaves of N. tobacum colonized by P. indica was significantly lower than that in un-colonized plants. The Proline content in the leaves colonized by P. indica was significantly higher than that in un-colonized ones; RT-PCR analysis showed that the expression level of Hsp90-1to Hsp90-4in colonized was significantly lower than that un-colonized ones, they reduced23.1%、33.3%、58.3%、47.4%compared with the un-colonized ones respectively. The expression level of Hsp90-5to Hsp90-7in colonized ones was significantly higher than that in un-colonized ones, the expression level was2.5、1.3、2.4folds than un-colonized ones respectivel. Indicating that symbiotic fungus can improve the drought resistance of N. tobacum, through maintaining cell biomembrane system stability and cell osmotic pressure, and reducing the level of membrane lipid peroxidation of plant, and regulate the expression of drought-related genes.3、The effect of Piriformospora indica on Nicobiana tobacum heavy metalIn order to confirm the influence of P. indica on heavy metal of Nicobiana tobacum, hydroponic, pot and field experiments were conducted, the Cd, Cr, Pb content in colonized and un-colonized plants were analyzed under Cd, Cr and Pb stresses. We also tested the the differences of MDA, proline, Chloroyll contents and the activities of CAT, POD and SOD and the expression level of genes Phytochelatins synthesis(Gsh2、TaPCS1、oas1), guaiacol peroxidase(GPX) and Hsp70between plants colonized and un-colonized by P. indica. The results showed that P.indica can reduce Cd, Cr and Pb content in N. tobacum leaves, but increase they content in plant roots in hydroponic experiments. Cd、Cr、Pb contents in P.indica colonized leaves of pot and field experiments were significantly lower than the control.The concentration of MDA in the leaves of N. tobacum colonized by P. indica was significantly lower than that in un-colonized plants. The Proline, Chloroyall content and the activities of CAT, POD and SOD in the leaves colonized by P. indica were significantly higher than that in un-colonized ones; RT-PCR analysis showed that the expression level of genes Gsh2、TaPCS1、oasl、GPX, Hsp70in colonized plants was4.3、1.4、2.9、1.7、6.9folds than un-colonized ones respectively.