Plant Breeding Department, Wageningen University and Research, Wageningen, The Netherlands.
Microbiology Faculty of Science, Utrecht University, Utrecht, The Netherlands.
PLoS One. 2020 Nov 4;15(11):e0241749. doi: 10.1371/journal.pone.0241749. eCollection 2020.
Pleurotus ostreatus, one of the most widely cultivated edible mushrooms, produces high numbers of spores causing severe respiratory health problems for people, clogging of filters and spoilage of produce. A non-sporulating commercial variety (SPOPPO) has been successfully introduced into the market in 2006. This variety was generated by introgression breeding of a natural mutation into a commercial variety. Our cytological studies revealed that meiosis in the natural and derived sporeless strains was blocked in metaphase I, apparently resulting in a loss of spore formation. The gene(s) underlying this phenotype were mapped to an 80 kb region strongly linked to sporelessness and identified by transformation of wild type genes of this region into a sporeless strain. Sporulation was restored by re-introduction of the DNA sequence encoding the P. ostreatus meiotic recombination gene MSH4 homolog (poMSH4). Subsequent molecular analysis showed that poMSH4 in the sporeless P. ostreatus was interrupted by a DNA fragment containing a region encoding a CxC5/CxC6 cysteine cluster associated with Copia-type retrotransposons. The block of meiosis in metaphase I by a poMSH4 null mutant suggests that this protein plays an essential role in both Class I and II crossovers in mushrooms, similar to animals (mice), but unlike in plants. MSH4 was previously shown to be a target for breeding of sporeless varieties in P. pulmonarius, and the null mutant of the MSH4 homolog of S. commune (scMSH4) confers an extremely low level of spore formation. We propose that MSH4 homologs are likely to be a breeding target for sporeless strains both within Pleurotus sp. and in other Agaricales.
糙皮侧耳（平菇）是最广泛种植的食用菌之一，其产生大量孢子，会对人类的呼吸系统健康造成严重问题，导致过滤器堵塞和农产品变质。2006 年，一种不产孢子的商业品种（SPOPPO）已成功推向市场。该品种是通过将自然突变体导入商业品种进行基因渗入杂交选育而来。我们的细胞学研究表明，自然和衍生的无孢子菌株的减数分裂在中期 I 被阻断，显然导致孢子形成的丧失。该表型的基因（s）被映射到一个 80kb 的区域，该区域与无孢子性强烈连锁，并通过将该区域的野生型基因转化为无孢子菌株来鉴定。通过将编码 P. ostreatus 减数分裂重组基因 MSH4 同源物（poMSH4）的 DNA 序列重新引入到无孢子菌株中，恢复了孢子形成。随后的分子分析表明，无孢子糙皮侧耳中的 poMSH4 被一个包含编码与 Copia 型逆转录转座子相关的 CxC5/CxC6 半胱氨酸簇的 DNA 片段的中断。poMSH4 缺失突变体在中期 I 阻断减数分裂表明，该蛋白在蘑菇中（与动物（小鼠）相似）但与植物不同，在 I 类和 II 类交叉中发挥重要作用。MSH4 先前被证明是在 P. pulmonarius 中培育无孢子品种的目标，而 S. commune （scMSH4）的 MSH4 同源物的缺失突变体赋予极低水平的孢子形成。我们提出，MSH4 同源物可能是糙皮侧耳属内和其他伞菌目中无孢子菌株的育种目标。
