Transcriptional changes of aquaporin genes in leaves of black medic induced by arbuscular mycorrhizal fungal inoculation under water deficit

One of the current research directions in plant-microbe interactions focuses on the mechanisms of plant adaptation to environmental stress through symbioses with various microorganisms. While the role of arbuscular mycorrhizal fungi in plant adaptation to drought is well-known, the underlying mechanisms of these processes remain poorly understood, particularly in leaf tissues. It is suggested that certain genes from the aquaporin family play a critical role both in adaptation to water deficit and in the development of an effective arbuscular mycorrhizal symbiosis. Thus, the important task in this study of plant-microbe symbioses is to assess the effect of arbuscular mycorrhizal fungal inoculation on the expression of aquaporin genes in leaves. This study utilizes the highly effective plant-microbe model system "Medicago lupulina + Rhizophagus irregularis" under drought stress conditions. A comparative assessment of gene transcription was carried out using the 2-ΔΔCT method based on real-time quantitative PCR results: normalization was performed relative to the actin reference gene with non-inoculated plants serving as the control. The study was conducted both at the initial development stage (the 2nd leaf stage), and at the stage of active plant-microbe interaction (the flowering stage). The study revealed genes with significant differential expression under drought conditions when comparing mycorrhizal and non-mycorrhizal Medicago lupulina plants: NIP3;1, NIP4;2, specific NIP7;1, TIP5;1 at the 2nd leaf stage; genes NIP3;1, NIP5;1, NIP6;4, NIP7;1 (specific), PIP1;4, TIP2;3 and specific XIP1;1 at the flowering stage. Previously, in a similar experiment, under well-watering conditions, the same genes did not have differential expression between mycorrhizal and non-mycorrhizal plants. Thus, the listed genes likely participate in the adaptation of the studied plants to drought conditions. The obtained information can be used to develop highly productive plant-microbe systems involving arbuscular mycorrhizal fungi, aimed at transitioning to organic farming, minimizing negative environmental impact, and enhancing plant resistance to water deficit.