Hammondia hammondi, an avirulent relative of Toxoplasma gondii, has functional orthologs of known T. gondii virulence genes.
Hammondia hammondi, an avirulent relative of Toxoplasma gondii, has functional orthologs of known T. gondii virulence genes.
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Hammondia hammondi 是弓形虫的无毒近亲，具有已知弓形虫毒力基因的功能直向同源物。
DOI：
10.1073/pnas.1304322110
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发表时间：
2013
影响因子：
11.1
通讯作者：
Boyle,JonP
中科院分区：
文献类型：
--
作者：
Walzer,KatelynA;Adomako-Ankomah,Yaw;Dam,RachelA;Herrmann,DalandC;Schares,Gereon;Dubey,JitenderP;Boyle,JonP
Toxoplasma gondiiis a ubiquitous protozoan parasite capable of infecting all warm-blooded animals, including humans. Its closest extant relative,Hammondia hammondi,has never been found to infect humans and, in contrast toT. gondii, is highly attenuated in mice. To better understand the genetic bases for these phenotypic differences, we sequenced the genome of aH. hammondiisolate (HhCatGer041) and found the genomic synteny betweenH. hammondiandT. gondiito be >95%. We used this genome to determine theH. hammondiprimary sequence of two majorT. gondiimouse virulence genes,TgROP5andTgROP18. When we expressed these genes inT. gondii, we found thatH. hammondiorthologs of TgROP5 and TgROP18 were functional. Similar toT. gondii, theHhROP5locus is expanded, and two distinct HhROP5 paralogs increased the virulence of aT. gondii TgROP5knockout strain. We also identified a 107 base pair promoter region, absent only in type IIITgROP18, which is necessary for TgROP18 expression. This result indicates that theROP18promoter was active in the most recent common ancestor of these two species and that it was subsequently inactivated in progenitors of the type III lineage. Overall, these data suggest that the virulence differences between these species are not solely due to the functionality of these key virulence factors. This study provides evidence that other mechanisms, such as differences in gene expression or the lack of currently uncharacterized virulence factors, may underlie the phenotypic differences between these species.
