Gao Qi, Yan Dong, Wang Dan, Gao Shanshan, Zhao Shuang, Wang Shouxian, Liu Yu
Institute of Plant and Environment Protection, Beijing Academy of Agriculture and Forestry Sciences, Beijing, China.
School of Agriculture, Ludong University, Yantai, China.
Front Microbiol. 2019 Sep 4;10:1987. doi: 10.3389/fmicb.2019.01987. eCollection 2019.
In basidiomycete fungi, the number of nuclei and their ploidy level per nucleus can vary tremendously among species; however, within species, nuclear number and ploidy levels are traditionally considered fixed in their vegetative hyphae. In the edible mushroom , the hyphae are classified as either monokaryotic or dikaryotic, with each monokaryotic hyphal cell containing one haploid nucleus, and each dikaryotic hyphal cell containing two haploid nuclei. The dikaryotic hyphae are the results of mating between two genetically distinct monokaryons with different mating types. In this study, we examined the nuclear number and size (a potential correlate to ploidy) of mycelia throughout its vegetative growth. We found that the number of nuclei within individual hyphal cells varied widely from non-nucleated to uninucleated, dinucleated, and multinucleated. Additionally, different nuclei within the same cell appeared very different in size, with a maximum nucleus cross-sectional area of 4.94 μm and the minimum nucleus cross-sectional area at only 0.37 μm. Moreover, as culture time increased, more cells appeared to be devoid of any nuclei, with transmission electron microscopy and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assays of late-stage cultures showing autophagosomes fusing and dissolving the nuclei and resulting in a large number of TUNEL-positive DNA fragments in non-nucleated cells. These results indicated that non-nucleated cells were likely caused by autophagy and apoptosis-like activities within aging hyphae.
在担子菌纲真菌中，不同物种间每个细胞核中的细胞核数量及其倍性水平差异极大；然而，在同一物种内，传统上认为其营养菌丝中的细胞核数量和倍性水平是固定的。在食用蘑菇中，菌丝被分为单核或双核，每个单核菌丝细胞含有一个单倍体细胞核，每个双核菌丝细胞含有两个单倍体细胞核。双核菌丝是两个具有不同交配型的遗传上不同的单核体之间交配的结果。在本研究中，我们在整个营养生长过程中检查了菌丝体的细胞核数量和大小（与倍性潜在相关）。我们发现，单个菌丝细胞内的细胞核数量差异很大，从无核到单核、双核和多核。此外，同一细胞内的不同细胞核在大小上差异非常明显，最大细胞核横截面积为4.94μm，最小细胞核横截面积仅为0.37μm。而且，随着培养时间的增加，更多细胞似乎没有任何细胞核，对后期培养物进行透射电子显微镜和末端脱氧核苷酸转移酶dUTP缺口末端标记（TUNEL）分析显示，自噬体融合并溶解细胞核，导致无核细胞中出现大量TUNEL阳性DNA片段。这些结果表明，无核细胞可能是衰老菌丝内自噬和类似凋亡活动的结果。
