Effect of <i>Rhizophagus irregularis</i> inoculation on aquaporin gene expression in the roots of <i>Medicago lupulina</i> in drought conditions

Background: Most terrestrial plants form a symbiosis with arbuscular mycorrhizal fungi. Arbuscular mycorrhiza significantly enhances plant growth and their adaptation to biotic and abiotic stress factors. Arbuscular mycorrhizal fungi help plant uptake and improve the water nutrition of host plant. At the same time, the regulation and transport of water in plants is largely determined by the aquaporins activity. The specificity of gene expression of these transporters in different plant species and in different tissues has not been fully studied. Aim: To evaluate the effect of mycorrhization of black medic by arbuscular mycorrhizal fungus on the expression of aquaporin genes in the roots under drought conditions at the early and late stages of symbiosis development. Methods: Medicago lupulina MlS-1 line, characterized by high response to mycorrhization, was selected by the authors and was used in this study. The effective Rhizophagus irregularis RCAM00320 strain was used for mycorrhization. The plants were watered daily by 0.6 volumes of saturated water content. But during one week before the results were recorded, water scarcity conditions were created, 0.4 volumes of saturated water content. The plants were counted on the 24th and 48th days after sowing and inoculation. Total RNA from plant roots was isolated using the trizole method with modifications. Thirty-three aquaporin genes were selected to analyze the expression levels. Changes in gene expression were assessed using the real-time polymerase chain reaction method. Results: It was shown the key genes involved in the mechanism of adaptation of mycorrhizal plants to drought may be NIP and TIP aquaporin genes, namely: MlNIP1;2, MlNIP1;3, MlNIP1;5, MlNIP4;1, MlNIP4;2 genes (mainly at the stage of the second leaf development) and MlTIP1;1, MlTIP1;4, MlTIP2;1, MlTIP2;2, MlTIP2;3, MlTIP3;1, MlTIP4;1, MlTIP5;1 genes (mainly at the flowering stage) in plant-microbial system “M. lupulina + R. irregularis”. The study used previously obtained data on the M. lupulina transcriptome to select target genes. Conclusion: The genes involved in the development of effective symbiosis of plants with arbuscular mycorrhizal fungi in conditions of drought were identified. New information about the mechanisms of effective symbiosis formation is of practical importance for the development of highly productive plant-microbial systems, which will allow the transition from intensive agricultural technologies to biological agriculture with the production of environmentally safe products.