Fachbereich Biologie, Universität Konstanz, 78457 Konstanz, Germany.
Mol Plant Pathol. 2004 May 1;5(3):183-9. doi: 10.1111/j.1364-3703.2004.00222.x.
SUMMARY The obligately biotrophic rust fungi are dependent on nutrient supply from their host plants. A cDNA library of infection structures of the rust fungus Uromyces fabae was used to identify a gene (UfAAT3) that encodes a protein with a high degree of sequence similarity to fungal amino acid permeases. The expression profile revealed by RT-PCR shows an up-regulation very early during rust development, with the highest level in haustoria and infected leaves. Heterologous expression of UfAAT3p in Xenopus oocytes revealed an amino acid permease energized by co-transport with protons and exhibiting a broad substrate specificity. Compared to the previously described U. fabae amino acid transporter (AAT1), which represented the highest transport activities for lysine and histidine, electrophysiological measurements with cRNA of UfAAT3-injected oocytes showed substrate preferences for leucine and the sulphur containing amino acids methionine and cysteine. The unique contribution of the amino acid permeases and their substrate affinities might be connected with the availability of amino acids in the leaf tissue. Thus, in order to compare the substrate profiles of AAT1p and UfAAT3p with the natural environment of U. fabae we analysed the amino acid concentration in the apoplastic space, in addition to that in extracts of Vicia faba leaves. The predominant free amino acids were asparagine, alanine, glutamine and glutamate. However, most amino acids were present at low concentrations (between 0.02 and 0.16 mm), including the preferred substrates of the U. fabae amino acid permeases AAT1p and UfAAT3p.
专性活体营养的锈菌依赖于其宿主植物的养分供应。使用锈菌 Uromyces fabae 的感染结构 cDNA 文库来鉴定一个基因（UfAAT3），该基因编码的蛋白质与真菌氨基酸转运蛋白具有高度的序列相似性。RT-PCR 显示的表达谱表明，在锈菌发育的早期就有上调表达，在吸器和感染的叶片中表达水平最高。在非洲爪蟾卵母细胞中异源表达 UfAAT3p 显示，该蛋白是一种由质子共转运驱动的氨基酸转运蛋白，具有广泛的底物特异性。与之前描述的 U. fabae 氨基酸转运蛋白（AAT1）相比，AAT1 对赖氨酸和组氨酸的转运活性最高，用 UfAAT3-injected 卵母细胞的 cRNA 进行的电生理测量表明，对亮氨酸和含硫氨基酸蛋氨酸和半胱氨酸具有底物偏好。氨基酸转运蛋白及其底物亲和力的独特贡献可能与叶片组织中氨基酸的可用性有关。因此，为了比较 AAT1p 和 UfAAT3p 与 U. fabae 的天然环境的底物谱，我们除了分析 Vicia faba 叶片提取物中外质空间中的氨基酸浓度外，还分析了 U. fabae 的氨基酸浓度。主要的游离氨基酸是天冬酰胺、丙氨酸、谷氨酰胺和谷氨酸。然而，大多数氨基酸的浓度都很低（0.02 到 0.16mm 之间），包括 U. fabae 氨基酸转运蛋白 AAT1p 和 UfAAT3p 的首选底物。
