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Expression Analysis of Aquaporins from Desert Truffle Mycorrhizal Symbiosis Reveals a Fine-Tuned Regulation Under Drought

¹Departamento Biología Vegetal (Botánica), Facultad de Biología, Universidad de Murcia, Campus de Espinardo, 30100 Murcia, Spain; ²Departamento de Microbiología del Suelo y Sistemas Simbióticos, Estación Experimental del Zaidín (CSIC), Profesor Albareda, no. 1, Granada 18008, Spain; ³Departamento de Riego, Centro de Edafología y Biología Aplicada del Segura (CEBAS-CSIC), 30100 Murcia, Spain; ⁴Istituto di Virologia Vegetale, CNR, Strada delle Cacce 73, 10135 Turin, Italy; ⁵Department of Agricultural, Forest and Food Sciences, University of Turin, Via Leonardo da Vinci 44, Grugliasco, 10095 Turin, Italy

We have performed the isolation, functional characterization, and expression analysis of aquaporins in roots and leaves of Helianthemum almeriense, in order to evaluate their roles in tolerance to water deficit. Five cDNAs, named HaPIP1;1, HaPIP1;2, HaPIP2;1, HaPIP2;2, and HaTIP1;1, were isolated from H. almeriense. A phylogenetic analysis of deduced proteins confirmed that they belong to the water channel proteins family. The HaPIP1;1, HaPIP2;1, and HaTIP1;1 genes encode functional water channel proteins, as indicated by expression assays in Saccharomyces cerevisiae, showing divergent roles in the transport of water, CO₂, and NH₃. The expression patterns of the genes isolated from H. almeriense and of a previously described gene from Terfezia claveryi (TcAQP1) were analyzed in mycorrhizal and nonmycorrhizal plants cultivated under well-watered or drought-stress conditions. Some of the studied aquaporins were subjected to fine-tuned expression only under drought-stress conditions. A beneficial effect on plant physiological parameters was observed in mycorrhizal plants with respect to nonmycorrhizal ones. Moreover, stress induced a change in the mycorrhizal type formed, which was more intracellular under drought stress. The combination of a high intracellular colonization, together with the fine-tuned expression of aquaporins could result in a morphophysiological adaptation of this symbiosis to drought conditions.