Noor Aziza I, Neyaz Marwa, Cook Daniel, Creamer Rebecca
Molecular Biology Program, New Mexico State University, Las Cruces, NM, 88001, USA.
Department of Entomology, Plant Pathology, and Weed Science, New Mexico State University, Las Cruces, NM, 88003, USA.
Curr Microbiol. 2020 Sep;77(9):2554-2563. doi: 10.1007/s00284-020-02111-2. Epub 2020 Jul 9.
Locoweeds are toxic leguminous plants in Astragalus and Oxytropis genera that contain fungal endophytes of Alternaria section Undifilum species. These fungi produce swainsonine, an alkaloid α-mannosidase inhibitor that causes a neurological syndrome, locoism in grazing animals. A SWN gene cluster has been identified in many swainsonine-producing fungi. The swnK gene, which is an essential component of the swainsonine biosynthetic pathway, encodes a polyketide synthase-nonribosomal peptide synthase (PKS-NRPS). To determine if swnK was conserved among Alternaria section Undifilum endophytes of locoweed, the sequence of the KS region of swnK was compared between various swainsonine-producing fungi. The internal transcribed spacer (ITS), and glyceraldehyde-3-phosphate dehydrogenase (GPD) regions from the same fungi were also assessed. Sequences were examined at the nucleotide and protein levels. Alternaria oxytropis, A. fulva, A. cinerea, and Alternaria sp. from Swainsona species produced distinct clades for all multigene data sets. swnK-KS sequence did not differ among fungi isolated from Astragalus mollissimus varieties or A. lentiginosus varieties. The swnK-KS amino acid sequence was essentially identical among all swainsonine-producing Alternaria sp. Two low swainsonine-producing fungi, Alternaria bornmuelleri and A. gansuense, clustered together, as did non-pathogen Alternaria endophytes. The swnK-KS sequence comparisons were effective in identifying swainsonine production capability and differentiating among swainsonine-producing fungal species.
疯草是黄芪属和棘豆属中的有毒豆科植物，其中含有链格孢属Undifilum组的真菌内生菌。这些真菌产生苦马豆素，一种生物碱α-甘露糖苷酶抑制剂，可导致放牧动物出现神经综合征——疯草中毒。在许多产生苦马豆素的真菌中已鉴定出一个SWN基因簇。swnK基因是苦马豆素生物合成途径的一个重要组成部分，编码一种聚酮合酶-非核糖体肽合酶（PKS-NRPS）。为了确定swnK在疯草的链格孢属Undifilum内生菌中是否保守，比较了各种产生苦马豆素的真菌之间swnK的KS区域序列。还评估了同一真菌的内部转录间隔区（ITS）和甘油醛-3-磷酸脱氢酶（GPD）区域。在核苷酸和蛋白质水平上检查序列。对于所有多基因数据集，棘豆链格孢、暗褐链格孢、灰链格孢以及来自无叶豆属物种的链格孢属菌株形成了不同的进化枝。从软毛黄芪变种或斑点黄芪变种中分离出的真菌之间，swnK-KS序列没有差异。在所有产生苦马豆素的链格孢属菌株中，swnK-KS氨基酸序列基本相同。两种低苦马豆素产生真菌，博恩米勒链格孢和甘肃链格孢聚集在一起，非致病性链格孢内生菌也是如此。swnK-KS序列比较在鉴定苦马豆素生产能力和区分产生苦马豆素的真菌物种方面是有效的。
