Sexual reproduction (SR), hallmarked by meiosis, is widespread in eukaryotes. In phytoplankton, SR has been observed in many lineages, but molecular information on SR or meiosis of harmful algal bloom (HAB) species is scarce. The raphidophyte Heterosigma akashiwo is a globally distributed and devastating HAB species, but molecular evidence of its SR or meiosis is lacking. Here, to address the gap of knowledge, the presence of meiotic genes in H. akashiwo were examined. Interestingly, seven meiosis-specific or related genes (SPO11, MND, RAD21, RAD51, MSH2, MSH6 and MEI2) were identified from H. akashiwo transcriptomes. Furthermore, expression patterns of these genes except MSH6 (excluded due to primer failure) were investigated using quantitative reverse-transcription PCR. Results showed that the examined genes exhibited similar diel rhythms, typically, highest in early dark period and then gradually decreasing until mid-day. In addition, the expression of these six genes was not higher in the stationary growth stage than in the exponential stage, as would be expected if meiosis was to form cysts, and their elevated expression in response to colchicine treatment (arresting cells in the G2/M transition) indicated a potential role of these genes in cell division and population growth in H. akashiwo. Consistent with this, we also found a morning to afternoon shift in the expression of these genes during the bloom of H. akashiwo. This study documents a part of the typical SR gene repertoire and its potential role in regulating cell division in H. akashiwo, offering candidates for population growth markers for bloom monitoring although its linkage to meiosis and SR remain to be studied further in the future.

以减数分裂为特征的性生殖（SR）在真核生物中很普遍。在浮游植物中，在许多谱系中都观察到了SR，但是关于SR或有害藻华（HAB）物种减数分裂的分子信息很少。蝴蝶藻类杂种赤足鱼是全球分布和破坏性的HAB物种，但缺乏其SR或减数分裂的分子证据。在这里，为了解决知识的空白，H中存在减数分裂基因。akashiwo被检查了。有趣的是，七个减数分裂特异或相关基因（SPO11，MND，RAD21，RAD51，MSH2，MSH6和MEI2）是从akashiwo转录组中鉴定出来的。此外，使用定量逆转录PCR研究了除MSH6外的这些基因的表达模式（由于引物失效而被排除）。结果显示，所检查的基因表现出相似的diel节律，通常在早期的黑暗时期最高，然后逐渐降低直至中午。此外，这六个基因的表达在稳定生长期并不高于指数生长期，这是减数分裂形成囊肿及其响应秋水仙碱处理而升高的表达所预期的（G2 / 3中的阻滞细胞）。 M过渡）表明这些基因在akashiwo的细胞分裂和种群增长中具有潜在作用。与此相一致，我们还发现了H盛开期间这些基因的表达从早上到下午发生了变化。赤尾窝。这项研究记录了典型的SR基因谱系的一部分及其在调节H细胞分裂中的潜在作用。akashiwo，尽管它与减数分裂和SR的联系仍有待进一步研究，但仍为人口增长标记物的开花监测提供了候选者。