Anthony Ossai Ukpene 1*, John C. Morka 2 and Thelma Ewere. Konyeme 3
1Department of Biological Sciences, Faculty of Science, University of Delta, Agbor, Nigeria; 2Department of Physics, Faculty of Science, University of Delta, Agbor, Nigeria; 3Department of Biological Sciences, Faculty of Science, University of Delta, Agbor, Nigeria
*Corresponding author: anthony.ukpene@unidel.edu.ng
The study aimed to examine the epigenetic and physiological mechanisms in Arabidopsis thaliana and Oryza sativa under cadmium (Cd) and lead (Pb) stress, an increasing concern due to heavy metal pollution, and to investigate how plants can withstand these stresses. The experiment investigated changes in DNA methylation, histone modifications, and gene expression in response to metal stress. Data were obtained through bisulfite sequencing and the ChIP-qPCR test (chromatin immunoprecipitation with a QIAcube automated nucleic acid purification system and real-time PCR system), and the gene expression was observed through RT-qPCR. Physiological parameters, including biomass, chlorophyll content, electrolyte leakage, and metal accumulation, were determined using spectrophotometry and atomic absorption spectroscopy. ANOVA and Pearson correlation coefficients were used to test significance and relationships. The results revealed that the exposure to Cd and Pb caused widespread reprogramming of the epigenome: in Arabidopsis, MET1 concentrations dropped by 45% during Cd stress, and ROS1 concentrations rose by 60%, leading to a 20% decrease in global methylation. Promoters of metal homeostasis genes were enriched for histone marks H3K4me3 and H3K27me3 and were associated with a two- to threefold increase in detoxification gene expression. Physiologically, there was a decrease in growth of up to 30% and a 50% growth in root metallic content of treated plants. The findings indicate that epigenetic alterations are important in mediating plant responses to heavy metal stress and could serve as biomarkers for the development of tolerant crop genotypes and for enhancing phytoremediation.