A gene from the arbuscular mycorrhizal fungus Glomus intraradices encoding a binding protein is up-regulated by drought stress in some mycorrhizal plants

The contribution of the arbuscular mycorrhizal (AM) symbiosis to plant drought tolerance results from a combination of physical, nutritional and cellular effects. However, the exact mechanisms involved in such enhanced tolerance are still a matter of debate. In this study a BiP-encoding gene from the AM fungus Glomus intraradices has been identified after differential hybridization of a cDNA library constructed from the fungus growing in vitro and subjected to drought stress by addition of 25% PEG 6000. Results show that its expression was up-regulated by drought stress not only during in vitro conditions (AM monoxenic cultures) but also ex vitro, when forming natural symbioses with plants. The identification of GiBiP gene provides new evidences that the contribution of AM fungi to the enhanced drought tolerance of the host plant can be mediated by proteins with chaperone-like activity, such as that of BiP. (c) 2006 Elsevier B.V. All rights reserved.