Sexual cycle and horizontal transmission of the grass symbiont, Epichloe typhina
Sexual cycle and horizontal transmission of the grass symbiont, Epichloe typhina
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DOI：
10.1017/s0953756296002602
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发表时间：
1997-03-01
影响因子：
--
通讯作者：
Schardl, CL
中科院分区：
文献类型：
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作者：
Chung, KR;Schardl, CL
猫尾草是禾本科植物的一种共生体，其有性状态在未成熟的寄主花序上。E. typhina产生精子，也是交配时的雌性结构。受精后，有一个致密的菌丝体的增殖，这被认为是异形。在加厚的基质中形成石被膜。本研究探讨了在交配过程中异核体形成的可能性以及子囊孢子在大肠杆菌侵染传播中的作用。伤寒。在几乎所有的情况下，相反交配型的精子体转移到基质中会导致基质增厚;然而，只有当亲本属于相同的交配群体时，才会产生子囊孢子。由一个精细胞亲本的部分基质的受精通常抑制由另一个菌株在基质上的其他地方取决于精细胞分离物使用的受精。异核体形成的测试是通过在交配后培养不产生子囊孢子的子座来进行的，以避免分析减数分裂产物。在两种情况下，雌性是培养的，在两种情况下，核和线粒体单倍型主要是雄性。在另一个例子中，来自雌性的线粒体单倍型和线粒体质粒与雄性核单倍型相关。这些结果表明，交配后，男性菌丝增殖和异核体有时可能会形成，也增殖。为了测试子囊孢子如何介导感染，未感染的多年生黑麦草植物的花序被受精的子座包围，E.将香蒲孢囊孢子排出，收集种子并使其生长，鉴定新感染的后代植物，并对来自5个后代植物的分离物进行遗传分析。正如预期的子囊孢子后代的rDNA单倍型的基质和精子的父母分离，而所有5个菌株的线粒体DNA的基质配置文件。这一观察结果表明，子囊孢子介导新寄主植物的感染。
Epichloe typhina is a biotrophic symbiont of grasses with its sexual state on immature host inflorescences. The ectophytic, presexual structure (stroma) of E. typhina produces spermatia and also serves as the female structure in mating. After fertilization there is proliferation of a dense mycelium which has been suggested to be heterokaryotic. Perithecia form in the thickened stroma. We investigated the possible formation of heterokaryons in matings and the role of ascospores in contagious spread of E. typhina. In almost all instances the transfer to a stroma of spermatia of opposite mating type leads to thickening of the stroma; however, ascospores were produced only if the parents were of the same mating population. Fertilization of part of a stroma by one spermatial parent often inhibited fertilization by another strain elsewhere on the stroma depending upon the spermatial isolates used. Tests for heterokaryon formation were performed by culturing stromata after matings that produced no ascospores, to avoid analysing meiotic products. In two instances the female was cultured, and in two the nuclear and mitochondrial haplotypes were primarily of the male. In another instance mitochondrial haplotypes and mitochondrial plasmids from the female became associated with the male nuclear haplotype. These results suggest that, following mating, male hyphae proliferate and heterokaryons may sometimes form and also proliferate. To test how ascospores mediate infection, inflorescences of uninfected perennial ryegrass plants were surrounded by fertilized stromata from which E. typhina ascospores were being ejected, seeds were collected and grown, newly infected progeny plants were identified, and isolates from five progeny plants were analysed genetically. As expected for ascospore progeny the rDNA haplotype of the stromal and spermatial parents had segregated, whereas all five isolates had the stromal profile of mitochondrial DNA. This observation demonstrated that ascospores mediate infection of new host plants.