State Key Laboratory of Crop Stress Biology in Arid Areas and College of Plant Protection, Northwest A&F University, Yangling, Shaanxi Province, China.
Department of Plant Pathology, University of Florida, Gainesville, Florida, USA.
Appl Environ Microbiol. 2021 May 26;87(12):e0047421. doi: 10.1128/AEM.00474-21.
The genetic regulation of () sexual reproduction does not strictly adhere to the Ascomycota paradigm and remains poorly understood. Morphologically different but sexually compatible strain types, termed plus and minus, have been recognized, but the biological and molecular distinctions between these strain types remain elusive. In this study, we characterized the sexual behaviors of a pair of plus and minus strains of with the aid of live-cell nucleus-localized fluorescent protein labeling, gene expression, and gene mutation analyses. We confirmed a genetically stable plus-to-minus switching phenomenon and demonstrated the presence of both cross-fertilized and self-fertilized perithecia within the mating line (perithecia cluster at the line of colony contact) between plus and minus strains. We demonstrated that pheromone signaling genes (a-factor-like and α-factor-like pheromones and their corresponding GPCR receptors) were differently expressed between vegetative hyphae of the two strains. Moreover, deletion of (a FUS/KSS1 mitogen-activate protein kinase) in the minus strain severely limited mating line formation, whereas deletion of a GPCR (FGSG_05239 homolog) and two histone modification factors (, ) in the minus strain did not affect mating line development but altered the ratio between cross-fertilization and self-fertilization within the mating line. We propose a model in which mating line formation in involves enhanced protoperithecium differentiation and enhanced perithecium maturation of the minus strain mediated by both cross-fertilization and diffusive effectors. This study provides insights into mechanisms underlying the mysterious phenomenon of plus-minus-mediated sexual enhancement being unique to fungi. Plus-minus regulation of sexual differentiation was reported in the early 1900s. Both plus and minus strains produce fertile perithecia in a homothallic but inefficient manner. However, when the two strain types encounter each other, efficient differentiation of fertile perithecia is triggered. The plus strain, by itself, can also generate minus ascospore progeny at high frequency. This nontypical mating system facilitates sexual reproduction and is specific; the underlying molecular mechanisms, however, remain elusive. The current study revisits this longstanding mystery using as an experimental system. The presence of both cross-fertilized and self-fertilized perithecia within the mating line was directly evidenced by live-cell imaging with fluorescent markers. Based on further gene expression and gene mutation analysis, a model explaining mating line development (plus-minus-mediated sexual enhancement) is proposed. Data reported here have the potential to allow us to better understand mating and filamentous ascomycete sexual regulation.
（）有性生殖的遗传调控并不严格遵循子囊菌模式，因此仍知之甚少。已经识别出形态不同但有性亲和的菌株类型，称为“+”和“-”，但这些菌株类型之间的生物学和分子差异仍然难以捉摸。在这项研究中，我们借助活细胞核定位荧光蛋白标记、基因表达和基因突变分析，对一对“+”和“-”菌株的有性行为进行了表征。我们证实了一种遗传上稳定的“+”到“-”的转换现象，并证明了在“+”和“-”菌株之间的交配线（菌落接触线处的产囊体簇）内既有杂交产囊体，也有自交产囊体。我们证明了信息素信号基因（类似 a 因子和α因子的信息素及其相应的 GPCR 受体）在两个菌株的营养菌丝中表达不同。此外，在“-”菌株中缺失（一种 FUS/KSS1 丝裂原激活蛋白激酶）严重限制了交配线的形成，而在“-”菌株中缺失一个 GPCR（FGSG_05239 同源物）和两个组蛋白修饰因子（、）并不影响交配线的发育，但改变了交配线内杂交和自交的比例。我们提出了一个模型，即在交配线的形成中，“-”菌株通过杂交和扩散效应物介导的增强的原产囊体分化和增强的产囊体成熟，参与了这一过程。这项研究为理解神秘的“+”和“-”介导的性增强现象提供了机制方面的见解，这种现象是子囊菌所特有的。“+”和“-”对 的性分化的调控早在 20 世纪初就有报道。“+”和“-”菌株都以同宗但效率低下的方式产生可育产囊体。然而，当两种菌株类型相遇时，就会触发可育产囊体的有效分化。“+”菌株本身也可以以高频率产生“-”减数分裂孢子后代。这种非典型的交配系统促进了有性繁殖，并且是“”特有的；然而，其潜在的分子机制仍然难以捉摸。本研究使用作为实验系统，重新审视了这一长期存在的谜团。通过活细胞荧光标记的直接成像，直接证明了交配线内既有杂交产囊体，也有自交产囊体。基于进一步的基因表达和基因突变分析，提出了一个解释交配线发育（“+”和“-”介导的性增强）的模型。这里报道的数据有可能使我们更好地理解交配和丝状子囊菌的性调控。
