Fungus gardens of the basidiomycete Leucocoprinus gongylophorus sustain large colonies of leaf-cutting ants by degrading the plant material collected by the ants. Recent studies have shown that enzyme activity in these gardens is primarily targeted toward starch, proteins and the pectin matrix associated with cell walls, rather than toward structural cell wall components such as cellulose and hemicelluloses. Substrate constituents are also known to be sequentially degraded in different sections of the fungus garden. To test the plasticity in the extracellular expression of fungus-garden enzymes, we measured the changes in enzyme activity after a controlled shift in fungal substrate offered to six laboratory colonies of Atta cephalotes. An ant diet consisting exclusively of grains of parboiled rice rapidly increased the activity of endo-proteinases and some of the pectinases attacking the backbone structure of pectin molecules, relative to a pure diet of bramble leaves, and this happened predominantly in the most recently established top sections of fungus gardens. However, fungus-garden amylase activity did not significantly increase despite the substantial increase in starch availability from the rice diet, relative to the leaf diet controls. Enzyme activity in the older, bottom sections of fungus gardens decreased, indicating a faster processing of the rice substrate compared to the leaf diet. These results suggest that leaf-cutting ant fungus gardens can rapidly adjust enzyme activity to provide a better match with substrate availability and that excess starch that is not protected by cell walls may be digested by the ants rather than by the fungus-garden symbiont.

中文翻译：

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Atta cephalotes 真菌-花园酶活性在真菌底物发生变化后发生快速变化（Attini，Formicidae）

担子菌 Leucocoprinus gongylophorus 的真菌花园通过降解蚂蚁收集的植物材料来维持大量切叶蚂蚁。最近的研究表明，这些花园中的酶活性主要针对淀粉、蛋白质和与细胞壁相关的果胶基质，而不是针对结构细胞壁成分，如纤维素和半纤维素。也已知底物成分在真菌园的不同部分依次降解。为了测试真菌花园酶的细胞外表达的可塑性，我们测量了提供给 Atta cephalotes 的六个实验室菌落的真菌底物受控转移后酶活性的变化。与纯黑莓叶饮食相比，仅由蒸谷米粒组成的蚂蚁饮食会迅速增加内切蛋白酶和一些果胶酶的活性，这些酶会攻击果胶分子的骨架结构，这主要发生在最近建立的顶部真菌花园的部分。然而，尽管大米日粮中淀粉的可用性显着增加，但与叶日粮对照相比，真菌花园淀粉酶活性并未显着增加。真菌园底部较旧的部分的酶活性降低，表明与叶子饮食相比，水稻底物的加工速度更快。