Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, Nova Scotia, Canada, B3M 2J6.
Department of Biology, Mount Saint Vincent University, 166 Bedford Highway, Halifax, Nova Scotia, Canada, B3M 2J6
Mycologia. 2015 Jan-Feb;107(1):1-11. doi: 10.3852/14-106. Epub 2014 Oct 24.
Fungal endophytes are ubiquitous in healthy root tissue, but little is known about their ecosystem functions, including their ability to utilize organic nutrient sources such as proteins. Root-associated fungi may secrete proteases to access the carbon and mineral nutrients within proteins in the soil or in the cells of their plant host. We compared the protein utilization patterns of multiple isolates of the root endophytes Phialocephala fortinii s.l., Meliniomyces variabilis and Umbelopsis isabellina with those of two ectomycorrhizal (ECM) fungi, Hebeloma incarnatulum and Laccaria bicolor, and the wood-decay fungus Irpex lacteus at pH values of 2-9 on liquid BSA media. We also assessed protease activity using a fluorescently labeled casein assay and gelatin zymography and characterized proteases using specific protease inhibitors. I. lacteus and U. isabellina utilized protein efficiently, while the ECM fungi exhibited poor protein utilization. ECM fungi secreted metallo-proteases and had pH optima above 4, while other fungi produced aspartic proteases with lower pH optima. The ascomycetous root endophytes M. variabilis and P. fortinii exhibited intermediate levels of protein utilization and M. variabilis exhibited a very low pH optimum. Comparing proteolytic profiles between fungal root endophytes and fungi with well defined ecological roles provides insight into the ecology of these cryptic root associates.
真菌内生菌广泛存在于健康的根组织中，但人们对其生态系统功能知之甚少，包括它们利用有机营养源（如蛋白质）的能力。与根相关的真菌可能会分泌蛋白酶来获取土壤或其植物宿主细胞内蛋白质中的碳和矿物质营养。我们比较了 Phialocephala fortinii s.l.、Meliniomyces variabilis 和 Umbelopsis isabellina 等多种根内生真菌与外生菌根真菌（ECM） Hebeloma incarnatulum 和 Laccaria bicolor 以及木质腐朽真菌 Irpex lacteus 的蛋白质利用模式，在 pH 值为 2-9 的液体 BSA 培养基上进行了比较。我们还使用荧光标记的酪蛋白测定法和明胶酶谱法评估了蛋白酶活性，并使用特定的蛋白酶抑制剂对蛋白酶进行了表征。I. lacteus 和 U. isabellina 有效地利用了蛋白质，而 ECM 真菌的蛋白质利用率则较低。ECM 真菌分泌金属蛋白酶，最适 pH 值高于 4，而其他真菌则产生具有较低最适 pH 值的天冬氨酸蛋白酶。子囊菌内生真菌 M. variabilis 和 P. fortinii 表现出中等水平的蛋白质利用能力，而 M. variabilis 则表现出非常低的 pH 最适值。比较真菌根内生菌和具有明确生态角色的真菌之间的蛋白水解谱，为这些隐生性根伴生菌的生态学提供了深入了解。
