PDF(Pubmed)
Abstract：
Spores are important as dispersal and survival propagules in fungi. In this study we investigated the variation in number, shape, size and germination mode of ascospores in Morchella galilaea, the only species of the genus Morchella known to fruit in the autumn. Based on the observation of five samples, we first discovered significant variation in the shape and size of ascospores in Morchella. One to sixteen ascospores were found in the asci. Ascospore size correlated negatively with ascospore number, but positively with ascus size, and ascus size was positively correlated with ascospore number. We noted that ascospores, both from fresh collections and dried specimens, germinated terminally or laterally either by extended germ tubes, or via the production of conidia that were formed directly from ascospores at one, two or multiple sites. The direct formation of conidia from ascospores takes place within asci or after ascospores are discharged. Using laser confocal microscopy, we recorded the number of nuclei in ascospores and in conidia produced from ascospores. In most ascospores of M. galilaea, several nuclei were observed, as is typical of species of Morchella. However, nuclear number varied from zero to around 20 in this species, and larger ascospores harbored more nuclei. One to six nuclei were present in the conidia. Nuclear migration from ascospores to conidia was observed. Conidia forming directly from ascospores has been observed in few species of Pezizomycetes; this is the first report of the phenomenon in Morchella species. Morphological and molecular data show that conidial formation from ascospores is not found in all the specimens of this species and, hence, is not an informative taxonomic character in M. galilaea. Our data suggest that conidia produced from ascospores and successive mitosis within the ascus may contribute to asci with more than eight spores. The absence of mitosis and/or nuclear degeneration, as well as cytokinesis defect, likely results in asci with fewer than eight ascospores. This study provides new insights into the poorly understood life cycle of Morchella species and more broadly improves knowledge of conidia formation and reproductive strategies in Pezizomycetes.
摘要：
孢子作为真菌的传播和存活繁殖体非常重要。在这项研究中，我们调查了数量的变化，形状,羊肚菌子囊孢子的大小和萌发方式，羊肚菌属中已知的唯一一种在秋天果实。根据对五个样本的观察，我们首次发现羊肚菌中子囊孢子的形状和大小存在显著差异。在腹水中发现了一到十六个子囊孢子。子囊孢子大小与子囊孢子数负相关，但肯定的是，子囊孢子数与子囊孢子大小呈正相关。我们注意到子囊孢子，来自新鲜的收藏品和干燥的标本，通过延长的胚芽管最终或横向发芽，或者通过直接由子囊孢子形成的分生孢子的产生，两个或多个网站。从子囊孢子直接形成分生孢子发生在asci内或子囊孢子排出后。使用激光共聚焦显微镜，我们记录了子囊孢子和由子囊孢子产生的分生孢子中的细胞核数量。在大多数galilaea的子囊孢子中，观察到几个核，就像典型的羊肚菌一样。然而,在这个物种中，细胞核数量从零到大约20，更大的子囊孢子带有更多的原子核。分生孢子中存在一到六个核。观察到子囊孢子向分生孢子的核迁移。在少数种类的小孢子菌中观察到直接由子囊孢子形成的分生孢子；这是羊肚菌物种中这种现象的首次报道。形态和分子数据表明，在该物种的所有标本中都没有发现子囊孢子的分生孢子形成，因此，不是M.galilaea的信息分类特征。我们的数据表明，由子囊孢子产生的分生孢子和子囊内的连续有丝分裂可能会导致超过8个孢子的腹水。没有有丝分裂和/或核变性，以及胞质分裂缺陷，可能导致少于八个子囊孢子的asci。这项研究提供了对羊肚菌物种生命周期知之甚少的新见解，并更广泛地提高了对小孢子菌的分生孢子形成和繁殖策略的认识。
