Investigation of expression levels of genes affecting meat yield and quality in Gerze (hacıkadı) turkish native chicken breed

The Gerze chicken breed, one of the two native chicken breeds registered in Turkiye, is facing the danger of extinction due to its low productivity characteristics, and its breeding is decreasing day by day. Revealing and improving the productivity characteristics of the Gerze chicken breed and promoting its breeding by giving commercial identity to the breed's products will contribute to the preservation of the Gerze chicken breed's population. In this doctoral thesis study, conducted with the aim of supporting conservation strategies for the native Gerze chicken breed and providing foundational data for future research on the breed, the meat yield and meat quality characteristics of the Gerze chicken breed were examined at the gene expression (mRNA) level. In the study, the expression levels of genes involved in lipid metabolism (PPARγ, SCD, LPL), muscle development (MSTN, CAPN3, FOXO3), and purine biosynthesis (ADSL, AMPD1, AK1, ENTPD8, ATIC) pathways in Pectoralis major muscle tissues of both Gerze chicken breed and commercial hybrid chicken breed at two different growth stages (Gerze: 10 and 20 weeks old, hybrid: 4 and 8 weeks old) were investigated using RT-qPCR analysis. The study employed the GAPDH gene as the endogenous reference gene, and the expression levels of 11 genes were determined by computing the 2-ΔCq value using the Cq values collected from both distinct growth stages of Gerze and hybrid chicken breeds. The study findings indicate that the genes MSTN, CAPN3, and FOXO3, which serve as regulators of muscle development, were expressed more in the Gerze chicken breed in both sample periods compared to the hybrid breed (P<0.001). For PPARγ, involved in lipid biosynthesis, it was found that the Gerze chicken breed had significantly higher gene expression only in the first sampling period (P<0.05), while for the SCD and LPL genes, the Gerze chicken breed exhibited significantly higher gene expression in both sampling periods compared to the hybrid breed (P>0.001). Furthermore, it was observed that the genes involved in the biosynthesis of IMP, considered the most important indicator of meat flavor (ADSL, AMPD1, AK1, ENTPD8, ATIC), were expressed more in the Gerze chicken breed in both sampling periods (P<0.05 and P<0.001). This study represents the first investigation of the meat quality characteristics of the Gerze chicken breed, renowned for its meat quality and flavor dating back to the Ottoman Empire, at the gene expression level. Therefore, the findings obtained in this doctoral thesis may serve as fundamental data to contribute to future molecular breeding studies in the Gerze chicken breed.