Schüssler Arthur, Martin Holger, Cohen David, Fitz Michael, Wipf Daniel
Darmstadt University of Technology, Institute of Botany, Schnittspahnstrasse 10, 64287 Darmstadt, Germany.
Nature. 2006 Dec 14;444(7121):933-6. doi: 10.1038/nature05364.
The symbiotic relationships between mycorrhizal fungi and plants have an enormous impact on terrestrial ecosystems. Most common are the arbuscular mycorrhizas, formed by fungi belonging to the phylum Glomeromycota. Arbuscular mycorrhizal fungi facilitate the uptake of soil nutrients by plants and in exchange obtain carbohydrates, thus representing a large sink for atmospheric plant-fixed CO(2). However, how carbohydrates are transported through the symbiotic interface is still unknown. Here we report the characterization of the first known glomeromycotan monosaccharide transporter, GpMST1, by exploiting the unique symbiosis of a glomeromycotan fungus (Geosiphon pyriformis) with cyanobacteria. The GpMST1 gene has a very low GC content and contains six introns with unusual boundaries. GpMST1 possesses twelve predicted transmembrane domains and functions as a proton co-transporter with highest affinity for glucose, then mannose, galactose and fructose. It belongs to an as yet uncharacterized phylogenetic monosaccharide transporter clade. This initial characterization of a new transporter family involved in fungal symbiosis will lead to a better understanding of carbon flows in terrestrial environments.
菌根真菌与植物之间的共生关系对陆地生态系统有着巨大影响。最常见的是丛枝菌根，由球囊菌门的真菌形成。丛枝菌根真菌促进植物对土壤养分的吸收，并以碳水化合物作为交换，因此成为大气中植物固定二氧化碳的一个巨大汇。然而，碳水化合物如何通过共生界面运输仍不清楚。在这里，我们通过利用一种球囊菌门真菌（梨形地管菌）与蓝细菌的独特共生关系，报道了首个已知的球囊菌门单糖转运蛋白GpMST1的特性。GpMST1基因的GC含量非常低，包含六个具有异常边界的内含子。GpMST1拥有十二个预测的跨膜结构域，作为质子共转运体发挥作用，对葡萄糖亲和力最高，其次是甘露糖、半乳糖和果糖。它属于一个尚未被表征的系统发育单糖转运蛋白分支。对这个参与真菌共生的新转运蛋白家族的初步表征将有助于更好地理解陆地环境中的碳流。
