University of Guelph, Guelph, ON, Canada.
Parasit Vectors. 2024 Oct 13;17(1):428. doi: 10.1186/s13071-024-06498-w.
Coccidia are a group of intracellular protozoal parasites within the phylum Apicomplexa. Eimeria tenella, one of the species that cause intestinal coccidiosis in poultry, can cause significant mortality and morbidity. Diploid oocysts of Eimeria species are shed in the feces of an infected host and must sporulate to achieve infectivity. This process results in eight haploid infectious units, called sporozoites, held within a single oocyst. Each Eimeria spp. parasite possesses a single apicoplast and a single mitochondrion, both of which carry multiple copies of their respective organellar genomes. Reports of copy numbers of organellar genomes have varied widely.
We report the application of quantitative polymerase chain reaction (qPCR), supported by next-generation sequencing, for the quantification of the extranuclear genomes relative to the nuclear genome over the course of sporulation and following its completion.
At 64 elapsed hours, 93.0% of oocysts were fully sporulated; no increase in percent sporulation was observed after this time. Apicoplast relative genome copy number showed several significant shifts up to 72 elapsed hours, after which no significant shifts were observed. Oocysts were shed with approximately 60% the amount of apicoplast DNA present at 72 h, after which point no significant shifts in apicoplast genome relative abundance occurred. Mitogenome relative copy number showed only two significant shifts, from 16 to 24 elapsed hours and from 24 to 32 elapsed hours. Oocysts were shed with approximately 28% the amount of mitochondrial DNA that was present at the time sporulation was deemed morphologically complete, at 64 elapsed hours.
The characterization of the dynamics of genome abundance in exogenous stages sheds new light on the basic biology of Eimeria spp. and supports the use of extranuclear targets for molecular modes of parasite quantification and identification with improved sensitivity and accuracy.
球虫是顶复门（Apicomplexa）中一类细胞内原生动物寄生虫。柔嫩艾美耳球虫（Eimeria tenella）是一种引起家禽肠道球虫病的物种，可导致显著的死亡率和发病率。二倍体卵囊在感染宿主的粪便中排出，并必须经过孢子化才能获得感染力。这个过程会产生八个单倍体的感染单位，称为孢子，它们被包裹在一个单一的卵囊内。每个艾美耳球虫属寄生虫都有一个单一的质体和一个单一的线粒体，它们都携带多个各自的细胞器基因组副本。有关细胞器基因组拷贝数的报道差异很大。
我们报告了定量聚合酶链反应（qPCR）的应用，该方法得到下一代测序的支持，用于在孢子化过程中和完成后，相对于核基因组来定量非核基因组。
在 64 个小时的时间里，93.0%的卵囊完全孢子化；在此之后，孢子化的百分比没有增加。质体相对基因组拷贝数在 72 个小时前有几个显著的变化，此后没有观察到显著的变化。卵囊排出时，质体 DNA 的含量约为 72 小时时的 60%，此后质体基因组相对丰度没有明显变化。线粒体基因组相对拷贝数只发生了两次显著的变化，从 16 小时到 24 小时，从 24 小时到 32 小时。在 64 个小时的时间里，卵囊排出时，线粒体 DNA 的含量约为孢子化形态完成时的 28%。
对外源阶段基因组丰度动态的描述为艾美耳球虫属的基础生物学提供了新的认识，并支持使用非核靶标进行寄生虫定量和鉴定的分子模式，以提高灵敏度和准确性。
