The relative copy number of mitochondrial and chloroplast DNA in young and mature leaves of different grape varieties

Abstract

The copy number of DNA matrices of subcellular organelles (plants) can serve as an indicator of the intensity of photosynthesis and oxidative phosphorylation processes. We assessed the relative copy numbers (RCN) of mitochondrial and chloroplast DNA in young and mature leaves of three grape varieties: ‘Traminer Pink’, ‘Chardonnay’, and ‘Syrah’, grown under field conditions. Leaf samples (5–10 mg) were randomly selected from each group of plants for subsequent total DNA extraction. The qRTPCR reaction was performed using LightCycler 480 SYBR Green I Master Mix (LifeScience, Roche) and a LightCycler 96 Automatic Analyzer (Roche Life Science). The relative copy numbers of the NAD1 gene (mitochondrial DNA) and rps16 gene (chloroplast DNA) were determined using the GAPDH gene (chromosomal DNA) as a reference. Quantitative assessment was conducted using the 2--Ct и 2---Ct algorithms. It has been established that the relative copy number (RCN) values of chloroplast and mitochondrial DNA vary and depend on the grape variety and leaf maturity. RCN of chloroplast and mitochondrial DNA is significantly higher in mature grape leaves of all studied varieties, indicating a higher intensity of photosynthesis and oxidative phosphorylation in mature grape leaves compared to young leaves. When assessing the MacroErgic Balance (MEB) indicator, it can be concluded that from 2 to 4% of the energy obtained in chloroplasts through photosynthetic processes is used for the production of macroergic compounds in the mitochondria of various grape varieties in both young and mature leaves. The experimental scheme we have developed can be successfully used as a testing system to assess the potential yield of various grape varieties.