Effect of Rhizophagus irregularis on osmotic adjustment, antioxidation and aquaporin PIP genes expression of Populus × canadensis ‘Neva’ under drought stress

Drought is an abiotic stress that severely reduces plant growth. Responding to drought, plants would induce a series of physiological and biochemical changes. Colonization by arbuscular mycorrhizal (AM) fungi was reported beneficial in improving plants’ drought tolerance. However, the effect of AM fungi in improving drought tolerance of widely planted Populus spp. was rarely reported. The effect of AM fungus (Rhizophagus irregularis) on malondialdehyde (MDA) content, proline and soluble proteins content, antioxidative enzymes activates, relative water content (RWC) and water use efficiency (WUE), and the aquaporin PIP genes expression of Populus × canadensis ‘Neva’ leaves under well-watered and drought-stressed condition was evaluated. R. irregularis could colonize more than 80 % of poplar roots, reduce MDA and proline content, lower antioxidative enzymes activates, and down-regulate the expression of PIP2;1, PIP2;2. Meanwhile, R. irregularis could increase soluble protein content, increase RWC and WUE, and up-regulate the expression of PIP1;1, PIP1;3, PIP1;4, PIP1;5, PIP2;1, PIP2;2, and PIP2;3. In conclusion, R. irregularis could improve drought tolerance of P. canadensis by increasing RWC via regulation of aquaporin genes expression, and consequently increased WUE, lowered accumulation of osmotic adjustment molecule, reduced ROS accumulation and oxidative damage. Further studies focusing on the influence of AM fungi on specific aquaporin PIP gene location, function and expression in plant responding to drought stress are needed.