Biology subjects

Hoeppner, M.

Publications and source records attributed to Hoeppner, M..

3 recordsLinked to original sources

bioRxiv2022

Bacterial colonizers of Nematostella vectensis are initially selected by the host before interactions between bacteria determine further succession

The microbiota of multicellular organisms undergoes considerable changes during development but the general mechanisms that control community assembly and succession are poorly understood. Here, we use bacterial recolonization experiments in Nematostella vectensis as a model to understand general mechanisms determining bacterial establishment and succession. We compared the dynamic establishment of the microbiome on the germfree host and on inert silica. Following the dynamic reconstruction of microbial communities on both substrates, we show that the initial colonization events are strongly influenced by the host but not by the tube, while the subsequent bacteria-bacteria interactions are the main cause of bacterial succession. Interestingly, the recolonization pattern on adult hosts resembles the ontogenetic colonization succession. This process occurs independently of the bacterial composition of the inoculum and can be followed at the level of individual bacteria, suggesting that priority effects are neglectable for early colonization events in Nematostella. To identify potential metabolic traits associated with initial colonization success and potential metabolic interactions among bacteria associated with bacterial succession, we reconstructed the metabolic networks of bacterial colonizers based on their genomes. These analyses revealed that bacterial metabolic capabilities reflect the recolonization pattern, and the degradation of chitin might be a selection factor during early colonization of the animal. Concurrently, transcriptomic analyses revealed that Nematostella possesses two chitin synthase genes, one of which is upregulated during early recolonization. Our results show that early colonization events are strongly controlled by the host while subsequent colonization depends on metabolic bacteria-bacteria interactions largely independent of host development.

microbiology↗

bioRxiv2021

Occasional paternal inheritance of the germline-restricted chromosome in songbirds

All songbirds have one special accessory chromosome1-4, the so-called germline-restricted chromosome (GRC)4-7, which is only present in germline cells and absent from all somatic tissues. Earlier work on the zebra finch (Taeniopygia guttata castanotis) showed that the GRC is inherited only through the female line4,6,8,9 - like mitochondrial DNA7,9-12 - and is eliminated from the sperm during spermatogenesis5,7,9-11. Here we show that the GRC can also be paternally inherited. Confocal microscopy using GRC-specific FISH probes indicated that a considerable fraction of sperm heads (1-19%) in zebra finch ejaculates still contained the GRC. In line with these cytogenetic data, sequencing of ejaculates revealed that individual males from two families differed strongly and consistently in the number of GRCs in their ejaculates. Examining a captive-bred population of hybrids of the two zebra finch subspecies (T. g. guttata and T. g. castanotis) revealed that the descendants inherited their mitochondria from a castanotis mother but their GRC from a guttata father. Moreover, GRC haplotypes across nine different castanotis matrilines showed at best a weak tendency to be co-inherited with mtDNA haplotypes. Within castanotis, the GRC showed little variability, while the mtDNA of matrilines was highly divergent. This suggests that a single GRC haplotype has recently spread across the entire castanotis population, crossing the matriline boundaries via paternal spillover. Our findings raise the possibility that certain GRC haplotypes could selfishly spread through the population, via additional paternal transmission, thereby outcompeting other GRC haplotypes that were limited to strict maternal inheritance, even if this was partly detrimental to organismal fitness.

genomics↗

bioRxiv2019

A comparison of pedigree, genetic, and genomic estimates of relatedness for informing pairing decisions in two critically endangered birds.

Conservation management strategies for many highly threatened species include conservation breeding to prevent extinction and enhance recovery. Pairing decisions for these conservation breeding programmes can be informed by pedigree data to minimise relatedness between individuals in an effort to avoid inbreeding, maximise diversity, and maintain evolutionary potential. However, conservation breeding programmes struggle to use this approach when pedigrees are shallow or incomplete. While genetic data (i.e., microsatellites) can be used to estimate relatedness to inform pairing decisions, emerging evidence indicates this approach lacks precision in genetically depauperate species, and more effective estimates will likely be obtained from genomic data (i.e., thousands of genome-wide single nucleotide polymorphisms, or SNPs). Here, we compare relatedness estimates using pedigree-, genetic-, and genomic-based approaches for making pairing decisions in two critically endangered birds endemic to New Zealand: kak[i]/black stilt (Himantopus novaezelandiae) and k[a]k[a]riki karaka/orange-fronted parakeet (Cyanoramphus malherbi). Our findings indicate genetic-based estimates of relatedness are indeed the least precise when assessing known parent-offspring and full sibling relationships. Furthermore, our results show that relatedness estimates and subsequent pairing recommendations using PMx are most similar between pedigree- and genomic-based approaches. These combined results indicate that in lieu of robust pedigrees, SNPs are an effective tool for informing pairing decisions, which has exciting implications for many poorly pedigreed conservation breeding programmes worldwide.

molecular biology↗