Project 1.7

Mitochondrial haplotypes and phenotypes in laying hens

Martin Hasselmann / Korinna Huber

Mitochondria are involved in several organismic key processes; hence the in-depth characterization of mtDNA haplotypes and mt gene expression in hens with efficient phosphorus (P) utilization and myo-inositol metabolism is of utmost importance. Myo-inositol is known to modulate mitochondrial functionality by so far unknown mechanisms related to autophagy and mitophagy.

The project will obtain whole mitochondrial genome haplotypes for the two strains of laying hens. This approach determines potential mutations that arose during the genetic selection process in laying hens affecting key enzyme activities. The data will be combined with those of genome analyses obtained in other projects of the Research Unit to find associations of interacting loci depending on the nuclear background.

Further, mtDNA haplotypes are associated with the molecular information regarding metabolomics profiles assessed in another project. Thus, comprehensive insights into the functional importance of mitochondria in respect to P utilization and myo-inositol metabolism in hens will be gained.

Results

Fig. 1. Evolutionary relationship of the mitochondrial genome of laying hens shown as haplotype network (TCS algorithm) based on the mitochondrial genome (16784bp) of 180 laying hens.

We have established a pipeline to obtain full-length, high-quality mitochondrial (mt)-genome sequences using a long-range PCR amplicon sequencing approach in Heumann-Kiesler et al. 2021. Consequently, we have obtained mt-genomes from 180 laying hens representing the two different strains that result from two experimental setups. The mt-haplotypes were combined with performance data such as body weight, feed intake and phosphorus utilization to depict their influence on the hens during their productive life stages. A surprisingly low level of genetic diversity, combined with a reduced number of haplotypes were found (Fig. 1). We identified 13 segregating sites in the aligned data set, representing eight sites located in non-protein-coding regions (Control region, tRNA and rRNA) and five sites in protein coding genes. Haplotype-specific variation were detected in respect to different P/Ca diets and e.g. body growth varies not only between brown and white strain but in particular between the distinct mt-haplotypes of brown hens.

Gene expression data for all individuals of the two experiments have been obtained, focusing on mt-encoding genes and a set of nuclear genes (total n=48) in five tissues (liver, ovary, duodenum, ileum and breast muscle). Preliminary analyses show remarkable tissue and gene specific differences, between and within the two strains (Fig. 2) that will be linked to the focal trait, P utilization and the myo-inositol metabolism (Heumann-Kiesler et al., in prep.). Our data show the importance to gain a deeper understanding of the mito-nuclear interaction and mitochondrial function in laying hens.

Fig. 2 Heat map showing expression differences of the brown and white strain, including haplotypes on a subset of mitochondrial and interacting nuclear genes among three life stages and three tissues.
Project leaders

Prof. Dr. Martin Hasselmann
Institut für Nutztierwissenschaften, Fachgebiet für Populationsgenomik bei Nutztieren
+49 711 459 22481
E-mail

Prof. Dr. Korinna Huber
Institut für Nutztierwissenschaften, Fachgebiet für Funktionelle Anatomie der Nutztiere
+49 711 459 23998
E-mail

Staff

Clara Heumann-Kiesler
Institut für Nutztierwissenschaften, Fachgebiet für Populationsgenomik bei Nutztieren
+49 711 459 22487
E-mail

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