Botany, Ahead of Print.
Swainsonine, an indolizidine alkaloid, is an α-mannosidase and mannosidase II inhibitor that alters glycoprotein processing and causes lysosomal storage disease. Swainsonine is the toxic principle in several plant species worldwide and causes severe toxicosis in livestock grazing these plants. All swainsonine-containing plant taxa investigated to date are associated with fungal symbionts that produce swainsonine. Among the swainsonine-containing convolvulaceous species, Ipomoea carnea Jacq. is associated with a seed-transmitted symbiont belonging to the fungal order Chaetothyriales. The nature of this association was unclear; therefore, this association was investigated further using microscopy. Macroscopic and microscopic data reported here demonstrate that the Chaetothyriales symbiont associated with I. carnea grows ectopically on the adaxial (upper) surface of leaves as lacy mycelia in plants that contain swainsonine and was not present on plants lacking swainsonine that were derived from fungicide-treated seeds. Hyphae were not observed on the surface of any other tissues including the abaxial (lower) leaf surface, petiole, and stem. Mycelia were not visible in internal tissues below the epidermis, and there did not appear to be any hyphal extensions within the fibrovascular bundles or stomata. Longitudinal and (or) cross sections of the stems or petioles did not show evidence of hyphae growing between cells. These results suggest an epibiotic growth habit of the Chaetothyriales symbiont in association with I. carnea.

中文翻译：

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Chaetothyriales 真菌共生体在 Ipomoea carnea 上的异位生长

植物学，超前印刷。
Swainsonine 是一种吲哚里西啶生物碱，是一种 α-甘露糖苷酶和甘露糖苷酶 II 抑制剂，可改变糖蛋白加工并导致溶酶体贮积病。Swainsonine 是世界范围内若干植物物种的有毒成分，并在放牧这些植物的牲畜中引起严重中毒。迄今为止调查的所有含有八氢八角环素的植物分类群都与产生八氢八角环素的真菌共生体有关。在含有 swainsonine 的旋花物种中，Ipomoea carnea Jacq。与属于真菌目 Chaetothyriales 的种子传播共生体有关。这种关联的性质尚不清楚。因此，使用显微镜进一步研究了这种关联。这里报告的宏观和微观数据表明，毛壳菌目共生体与 I. carnea 在叶子的近轴（上）表面异位生长，作为含有八氢八角环素的植物中的花边菌丝体，而在来自杀菌剂处理的种子的缺乏八角心素的植物中不存在。在任何其他组织的表面上未观察到菌丝，包括背面（下部）叶表面、叶柄和茎。在表皮下方的内部组织中看不到菌丝体，并且在纤维血管束或气孔内似乎没有任何菌丝延伸。茎或叶柄的纵向和（或）横截面没有显示细胞间菌丝生长的证据。这些结果表明 Chaetothyriales 共生体的外生生长习性与 I. carnea 相关。