Large accumulation of mRNA and DNA point modifications in a plant senescent tissue

Although nucleic acids are the paradigm of genetic information conservation , they are inherently unstable molecules that suffer intrinsic and environm ental damage. Oxidative stress has been related to senescence and aging and , recently, it has been shown that mutations accumulate at high frequency i n mitochondrial DKA with age. We investigated RNA and DNA modifications in cork, a senescent plant tissue under high endogenous oxidative stress condi tions. When compared to normally growing young tissue, cork revealed an une xpected high frequency of point modifications in both cDNA (Pn = 1/1781) an d nuclear DNA (Pn = 1/1520). Cork should be viewed as a mosaic of genetical ly heterogeneous cells, This has biological implications: it supports somat ic mutation models for aging and challenges 'single cDNA clone' as descript or for the molecular genetics of senescent tissues. (C) 2000 Federation of European Biochemical Societies.