Invertebrates such as termites feeding on nutrient-poor substrate receive essential nitrogen by biological nitrogen fixation of gut diazotrophs. However, the diversity and composition of gut diazotrophs of vertebrates such as Plateau pikas living in nutrient-poor Qinghai-Tibet Plateau remain unknown. To fill this knowledge gap, we studied gut diazotrophs of Plateau pikas (Ochotona curzoniae) and its related species, Daurian pikas (Ochotona daurica), Hares (Lepus europaeus) and Rabbits (Oryctolagus cuniculus) by high-throughput amplicon sequencing methods. We analyzed whether the gut diazotrophs of Plateau pikas are affected by season, altitude, and species, and explored the relationship between gut diazotrophs and whole gut microbiomes. Our study showed that Firmicutes, Spirochaetes, and Euryarchaeota were the dominant gut diazotrophs of Plateau pikas. The beta diversity of gut diazotrophs of Plateau pikas was significantly different from the other three lagomorphs, but the alpha diversity did not show a significant difference among the four lagomorphs. The gut diazotrophs of Plateau pikas were the most similarly to that of Rabbits, followed by Daurian pikas and Hares, which was inconsistent with gut microbiomes or animal phylogeny. The dominant gut diazotrophs of the four lagomorphs may reflect their living environment and dietary habits. Season significantly affected the alpha diversity and abundance of dominant gut diazotrophs. Altitude had no significant effect on the gut diazotrophs of Plateau pikas. In addition, the congruence between gut microbiomes and gut diazotrophs was low. Our results proved that the gut of Plateau pikas was rich in gut diazotrophs, which is of great significance for the study of ecology and evolution of lagomorphs.
The genus Paraheligmonelloides Fukumoto, Kamiya and Suzuki, 1980 (Nippostrongylinae) is revised and split into four genera, mainly based on characters of the synlophe not previously considered at the supraspecific level. These characters mainly include the homology of the left ridge with ridge 1', the relative size of the right ridge to the left ridge and to ridge 1' and the distribution of the largest ridges. Paraheligmonelloides sensu stricto, characterized by the homology of the left ridge with ridge 1', contains only the type species, Paraheligmonelloides kenyensis Fukumoto, Kamiya and Suzuki, 1980, parasitic in a lagomorph from Kenya. Krishnasamyos n. gen., characterized by ridge 1' forming a comarete, two minute left ventral ridges and ridge 1 larger than other dorsal ridges, only includes the species Krishnasamyos triangulus n. comb., parasitic in Malaysian murids. Hughjonestrongylus n. gen., characterized by numerous ridges markedly unequal in size, with the largest ridges grouped in relation to the lateral fields, includes Hughjonestrongylus ennisae n. comb., Hughjonestrongylus amplicaudae n. comb., Hughjonestrongylus mirzai n. comb., and Hughjonestrongylus singauwaensis n. comb., all parasitic in murids from Papua Indonesia and Papua New Guinea. Syafruddinema n. gen., characterized by ridge 1 as long as other dorsal ridges and a gap associated with the left lateral field, between ridges 2' and 3', includes Syafruddinema paruromyos n. comb., Syafruddinema annandalei n. comb., and Syafruddinema eropeplios n. comb., parasitic in murids from Malaysia and Indonesia. A key to the proposed genera is provided.
APOBEC1 (A1) proteins from lagomorphs and rodents have deaminase-dependent restriction activity against HIV-1, whereas human A1 exerts a negligible effect. To investigate these differences in the restriction of HIV-1 by A1 proteins, a series of chimeric proteins combining rabbit and human A1s was constructed. Homology models of the A1s indicated that their activities derive from functional domains that likely act in tandem through a dimeric interface. The C-terminal region containing the leucine-rich motif and the dimerization domains of rabbit A1 is important for its anti-HIV-1 activity. The A1 chimeras with strong anti-HIV-1 activity were incorporated into virions more efficiently than those without anti-HIV-1 activity, and exhibited potent DNA-mutator activity. Therefore, the C-terminal region of rabbit A1 is involved in both its packaging into the HIV-1 virion and its deamination activity against both viral cDNA and genomic RNA. This study identifies the novel molecular mechanism underlying the target specificity of A1.