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

Abstract

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, CO 2 , and NH 3 . 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 wellwatered 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.

How tree roots respond to drought

“…However, some studies have not shown positive effects of ECM fungi on aquaporin gene expression. A recent study using Helianthemum almeriense and its fungal symbiont Terfezia claveryi was conducted to investigate the expression patterns of five aquaporin genes from the plant and one from its fungal symbiont ( Navarro-Ródenas et al, 2013 ). Results of this experiment indicated that the plant aquaporin genes were not enhanced in the roots by the ECM status and were even significantly reduced in one case.…”

Fungal Aquaporins in Ectomycorrhizal Root Water Transport

“…The studies demonstrate their strong to moderate capacity of transporting water, urea, glycerol, ammonia, and CO 2 . Their expression can be altered by mycorrhization or abiotic cues such as drought, salt, low temperature, or pH (Dietz et al, 2011;Navarro-Ródenas et al, 2012Xu et al, 2015), suggesting their multiple roles in plantfungal interactions, and their involvement in water transport and nutrient transfer of the mycorrhizal partners. Differential expressions of fungal aquaporins were also observed in a cellspecific pattern, in EcM root tips, free-living mycelium, fungal mantle, Hartig net, and fruiting body.…”

“…Secondly, the abundance and activity of fungal aquaporins could impact water availability in root extracellular space in Hartig net (Figures 1A,B). Ultimately, by changing the hydration in the apoplastic space, it can influence root aquaporin regulation and the overall root water uptake (Javot and Maurel, 2002;Marjanović et al, 2005;Lee et al, 2010;Dietz et al, 2011;Navarro-Ródenas et al, 2013;Xu et al, 2015;Calvo-Polanco et al, 2019).…”

Application of Arbuscular Mycorrhizae Glomus iranicum var. tenuihypharum var. nova in Intensive Agriculture: A Study Case

“…In the second year, the good water status of the grapevines, the higher percentage of root colonization and lower fruit load led to considerably higher values of both A and WUE in treatment T 1 [79]. In fact, AMF are known to exert a degree of control over transpiration, allowing plants to maintain high levels of WUE [80]. Such an increase, which agrees with other studies in vines [81], may also have accounted for the enhanced growth of plants colonized with Glomus species, most probably as a result of enhanced CO 2 fixation [49].…”