Integrity of nuclear DNA and physio-biochemical indicators of pisum sativum L. Seeds under accelerated aging

Abstract

Currently, much attention is paid to understanding the roles of DNA and the main mechanisms for ensuring stability of the genome in maintaining seed viability during aging. It is also shown that significant oxidative damage to DNA occurs during seed swelling, and active DNA restoration processes are a factor that facilitates the initiation of DNA replication and rapid germination of seeds. Our objective was to study, on the example of two pea varieties and their hybrid, the effect of accelerated seed aging on the level of DNA damage (by DNA comet method) and biochemical indicators (lipid peroxidation, peroxidase activity, content of low-molecular antioxidants) in cells of embryos during seed swelling to find a relationship between these parameters and the changes in physiological parameters of seed germination. It is shown that accelerated aging leads to changes in pea seed germination capacity which are varietal specific, as well as in the biochemical indicators studied. The least resistant to the accelerated aging was Melkosemyannyi 2 variety, and the seeds of Saryal variety were medium-resistant. The seeds of a hybrid of these varieties were the most resistant which may be due to the effect of heterosis. Seed aging causes a significant increase in DNA damage assessed as DNA per cent in the tail of the comet and/or atypical comets. The longer the seeds were under aging conditions, the higher was DNA fragmentation in cells of the embryos upon swelling. Under 24 weeks of accelerated aging, there was a 1.6-3.3 % increase in DNA found in the tail of the comet, and the number of atypical comets in the embryo cells increased 17-40-fold depending on the variety (hybrid) as compared to control. Probably, a significant reduction of seed physiological parameters was caused by higher degree of nuclear DNA fragmentation, decreased enzymatic antioxidants activity (in particular, activity of peroxidases) and intensified oxidation in embryos. Intensification of oxidative processes is expressed as a 2.5-fold excess of lipid peroxidation in germs of a rapidly aging variety which is accompanied by low seed germination. It is assumed that the increase in the degree of DNA damage is a consequence of the depletion of antioxidant and repair enzymes and indicates a slowdown or lack of regenerative processes in the embryos of aging seeds.