Piriformospora indica Improves Salt Tolerance in Nicotiana tobacum by Promoting the Synthesis of Osmolyte and Inducing the Expression of Stress Resistance Genes
Abstract：The root endophytic fungi Piriformospora indica has been shown to increase resistance against biotic stress and tolerance to abiotic stress in many plants. In order to study the influence of P. indica on salt tolerance in Nicotiana tobacum, we 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 with 300 mmol/L NaCl. The results showed that the MDA concentration and relative conductance in N. tobacum leaves colonized by P. indica were significantly lower compared with the un-colonized ones (P＜0.05) and the Pro content in P. indica colonized N. tobacum leaves was significantly higher than that in un-colonized ones (P＜0.05). RT-PCR analysis showed that the expression of salt tolerance gene(osmotin promoter binding protein) OPBP1 and pathogenesis-related (PR)protein genes PR-1a, PR2, PR3 and PR5 were 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 significantly higher than the un-colonized ones (P＜0.05), which 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. This study preliminarily confirmes the role and partly mechanism of salt tolerance of N. tobacum conferred by P. indica, and conforred the possibility of better understanding of the role and related mechanisms in P. indica colonized N. tobacum during stresses resistance.
