B Chromosomes' Sequences in Yellow-Necked Mice Apodemus flavicollis-Exploring the Transcription.

B chromosomes (Bs) are highly polymorphic additional chromosomes in the genomes of many species. Due to the dispensability of Bs and the lack of noticeable phenotypic effects in their carriers, they were considered genetically inert for a long time. Recent studies on Bs in Apodemus flavicollis revealed their genetic composition, potential origin, and spatial organization in the interphase nucleus. Surprisingly, the genetic content of Bs in this species is preserved in all studied samples, even in geographically distinct populations, indicating its biological importance. Using RT-PCR we studied the transcription activity of three genes (Rraga, Haus6, and Cenpe) previously identified on Bs in A. flavicollis. We analysed mRNA isolated from spleen tissues of 34 animals harboring different numbers of Bs (0-3).The products of transcriptional activity of the analysed sequences differ in individuals with and without Bs. We recorded B-genes and/or genes from the standard genome in the presence of Bs, showing sex-dependent higher levels of transcriptional activity. Furthermore, the transcriptional activity of Cenpe varied with the age of the animals differently in the group with and without Bs. With aging, the amount of product was only found to significantly decrease in B carriers. The potential biological significance of all these differences is discussed in the paper.

The prevalence of pathogenic forms of Leptospira in natural populations of small wild mammals in Serbia.

The greatest epidemiological significance of leptospirosis in Europe comes from the fact that it is the most widespread zoonosis in the world. However, epizootiological data, especially information on maintenance hosts such as small wild mammals, are largely missing. To fill this gap in data in Serbia, we used RT-PCR for the detection of pathogenic Leptospira species and analysed 107 animals belonging to six species of small wild mammals (Apodemus agrarius, Apodemus flavicollis, Microtus arvalis, Myodes glareolus, Microtus subterraneus and Sorex araneus) collected from two localities. The animals from the first locality that was situated in a tourist area, were collected for four consecutive years (2014-2017). We found persistent incidence of infection from year to year ranging from 6.67% to 78.57%. The average frequency of infected animals was 33.3% with the highest frequency in 2014, the year characterised by a very high number of flooding days. All animals proved to be infected with pathogenic Leptospira species that were collected from the second locality situated in an agricultural area in a single year, 2014. The findings show a variable but constant presence of pathogenic Leptospira species in populations of small wild mammals in the studied areas, which indicates the need for constant monitoring.

Population genetic structure of the Mediterranean horseshoe bat Rhinolophus euryale in the central Balkans.

Migratory behaviour, sociality and roost selection have a great impact on the population structure of one species. Many bat species live in groups, and movements between summer and hibernation sites are common in temperate bats. The Mediterranean horseshoe bat Rhinolophus euryale is a cave-dwelling species that exhibits roost philopatry and undertakes seasonal movements which are usually shorter than 50 km. Its distribution in Serbia is restricted to karstic areas in western and eastern parts of the country, with a lack of known roosts between them. In this study, microsatellite markers were used to evaluate genetic variation in this species in the Central Balkans. Specifically, spatial genetic structuring between geographic regions and relatedness within different colony types were assessed. All analysed loci were polymorphic, and there was no significant inbreeding coefficient recorded. A moderate degree of genetic differentiation among the sampled colonies was found, and significant isolation by distance was recorded. Our results revealed that populations show a tendency to segregate into three clusters. Unexpectedly, populations from Montenegro and Eastern Serbia tended to group into one cluster, while populations from Western Serbia and Slovenia represented second and third cluster, respectively. The majority of variance was partitioned within colonies, and only a small but significant portion among clusters. Average relatedness within colony members was close to zero, did not differ significantly between the different colony types, and kinship is unlikely to be a major grouping mechanism in this species.

Possible influence of B chromosomes on genes included in immune response and parasite burden in Apodemus flavicollis.

Genetic background underlying wild populations immune response to different parasites is still not well understood. We studied immune response to multiple infections and to competition between different parasite species at different developmental stages in population of yellow-necked mouse, Apodemus flavicollis. Quantitative real-time PCR was used to investigate associations of MHC II-DRB, IL-10 and Tgf-ß genes expressions with presence of intestinal parasites at different developmental stages. Furthermore, we were interested whether the host related characteristics (sex, age, body condition, presence of B chromosomes or expression of other genes) or characteristics of present parasites (number of adult parasites of each identified species, egg count of each parasite genus, total number of nematode individuals) affect differential expression of the studied genes. A significant invert association between the expression of MHC II-DRB and Tgf-ß gene was found, which together with absence of IL-10 association confirmed modified Th2 as the main type of immune response to nematode infections. Effect of recorded parasites and parasite life-cycle stage on expression levels of MHC II-DRB gene was detected only through interactions with host-related characteristics such as sex, age, and the presence of B chromosomes. The presence of B chromosomes is associated with lower expression level of Tgf-ß gene. Although the influence of host genetic background on parasite infection has already been well documented, this is the first study in mammals that gave presence of B chromosomes on immune response full consideration.