Journal Article

A Versatile Monosaccharide Transporter That Operates in the Arbuscular Mycorrhizal Fungus Glomus sp Is Crucial for the Symbiotic Relationship with Plants

Wippel, Kathrin, Requena, Natalia, Helber, Nicole, Sauer, Norbert, Hause, Bettina, Schaarschmidt, Sara

2011

Overview

For more than 400 million years, plants have maintained a mutualistic symbiosis with arbuscular mycorrhizal (AM) fungi. This evolutionary success can be traced to the role of these fungi in providing plants with mineral nutrients, particularly phosphate. In return, photosynthates are given to the fungus, which support its obligate biotrophic lifestyle. Although the mechanisms involved in phosphate transfer have been extensively studied, less is known about the reciprocal transfer of carbon. Here, we present the high-affinity Monosaccharide Transporter2 (MST2) from Glomus sp with a broad substrate spectrum that functions at several symbiotic root locations. Plant cell wall sugars can efficiently outcompete the Glc uptake capacity of MST2, suggesting they can serve as alternative carbon sources. MST2 expression closely correlates with that of the mycorrhiza-specific Phosphate Transported (PT4). Furthermore, reduction of MST2 expression using host-induced gene silencing resulted in impaired mycorrhiza formation, malformed arbuscules, and reduced PT4 expression. These findings highlight the symbiotic role of MST2 and support the hypothesis that the exchange of carbon for phosphate is tightly linked. Unexpectedly, we found that the external mycelium of AM fungi is able to take up sugars in a proton-dependent manner. These results imply that the sugar uptake system operating in this symbiosis is more complex than previously anticipated.

• Publisher: American Society of Plant Biologists
• Subject: Base Sequence / Biological Transport / Carbon / Carbon sources / cell walls / Fungal Proteins / Fungal Proteins - genetics / Fungal Proteins - metabolism / Fungi / Gene Library / gene silencing / genetics / Glomeromycota / Glomeromycota - genetics / Glomeromycota - physiology / Glomeromycota - ultrastructure / Glomus / Glucose / Glucose - metabolism / Homeostasis / Medicago truncatula / Medicago truncatula - microbiology / Medicago truncatula - physiology / metabolism / microbiology / Molecular Sequence Data / Monosaccharide Transport Proteins / Monosaccharide Transport Proteins - genetics / Monosaccharide Transport Proteins - metabolism / Monosaccharides / Mycelium / Mycelium - metabolism / mycorrhizae / Mycorrhizae - genetics / Mycorrhizae - physiology / Mycorrhizae - ultrastructure / mycorrhizal fungi / nutrients / Phosphates / Phosphates - metabolism / photosynthates / Phylogeny / physiology / Plant cells / Plant Roots / Plant Roots - microbiology / Plants / Protons / roots / Sequence Analysis, DNA / Signal Transduction / Substrate Specificity / Sugar / Sugars / Symbiosis / Symbiosis - physiology / transporters / ultrastructure / Xylose / Xylose - metabolism