The Coccidia is the largest group of parasites within the Apicomplexa, a phylum of unicellular, obligate parasites characterized by the possession of an apical complex of organelles and structures in the asexual stages of their life cycles, as well as by a sexual reproductive phase that occurs enterically in host animals. Coccidian sexual reproduction involves morphologically distinct microgametes and macrogametes that combine to form a diploid zygote and, ultimately, following meiosis and mitosis, haploid, infectious sporozoites, inside sporocysts within an oocyst. Recent transcriptomic analyses have identified genes involved in coccidian sexual stage development and reproduction, including genes encoding for microgamete- and macrogamete-specific proteins with roles in gamete motility, fusion and fertilization, and in the formation of the resilient oocyst wall that allows coccidians to persist for long periods in the environment. Transcriptomics has also provided important clues about the regulation of gene expression in the transformation of parasites from one developmental stage to the next, a complex sequence of events that may involve transcription factors such as the apicomplexan Apetala2 (ApiAP2) family, alternative splicing, regulatory RNAs and MORC (a microrchida homologue and regulator of sexual stage development in Toxoplasma gondii). The molecular dissection of coccidian sexual development and reproduction by transcriptomic analyses may lead to the development of novel transmission-blocking strategies.

球虫是 Apicomplexa 中最大的寄生虫群，Apicomplexa 是一种单细胞专性寄生虫门，其特征是在生命周期的无性阶段拥有一个由细胞器和结构组成的顶端复合体，以及发生的有性生殖阶段在宿主动物中肠道。球虫有性繁殖涉及形态上不同的小配子和大配子，它们结合形成二倍体受精卵，并最终在减数分裂和有丝分裂之后，在卵囊内的孢子囊内形成单倍体、传染性子孢子。最近的转录组学分析确定了参与球虫有性阶段发育和繁殖的基因，包括编码小配子和大配子特异性蛋白质的基因，这些蛋白质在配子运动、融合和受精中发挥作用，以及形成有弹性的卵囊壁，使球虫能够在环境中长期存在。转录组学还提供了关于在寄生虫从一个发育阶段到下一个发育阶段的基因表达调控的重要线索，一系列复杂的事件可能涉及转录因子，如 apicomplexan Apetala2 (ApiAP2) 家族、选择性剪接、调节 RNA和 MORC（一种微管同系物和性阶段发育的调节剂）弓形虫）。通过转录组学分析对球虫有性发育和繁殖的分子解剖可能会导致新的传播阻断策略的发展。