A preliminary study on DNA survival curves under simulated sedimentary environment
Li Chun-xiang, Cheng An-jin and Yang Qun
pp. 1-11, in English, with Chinese abstract
Preservational devices simulating natural sedimentary environment were designed to monitor DNA degradation/survival behavior through time under different environmental parameters. In this preliminary study, we used the leaves of Brassica chinensis Linnaeus as experimental material, preserved under two simulating environmental conditions: A) 30°C; B) 10°C; both conditions A and B are partially deoxygenated by applying a negative pressure inside the sample container and in aquatic environment. Samples were collected in 2-day intervals. The total nucleic acids extracted from the time-series samples, which also include DNA of microbial organisms that penetrated the leaf tissues during the simulating preservation, display an apparent degradational trend. Further detection of DNA survival within the samples was conducted using quantitative PCR method with plant-specific primers and DNA survival curves were obtained for the initial 14-day experimental period under the simulating conditions. It is found that the rate of DNA degradation under Condition A may reach up to about 4,400 times that under Condition B; and in both conditions, the PCR amplificability for the 200 bp-size DNA fragment is markedly different from that for the 630 bp-size fragment as shown with the regressive curves from the simulation data. Based on PCR analysis, it is found that DNA survival curve follows an exponential equation as shown with the regressive curves from the simulation data. Further studies are being conducted with regard to differences caused by changing humidity, oxygen content, and types of organic tissues.
Keywords: molecular palaeontology, molecular taphonomy, old DNA, DNA degradation, simulated environment, PCR