Abstract
After the nuclear accident in Chernobyl, environmental effects of radiation have appeared remarkably in conifers such as pine trees in the surrounding forests. Depending on the exposed radiation levels, the conifers have showed growth inhibition, malformation of needles, reproductive loss and withering. For investigations of cellular mechanisms relating to the radiation damages, we assessed radiation–induced cell death in suspension cell culture of Japanese native conifer, Japanese cedar (Cryptomeria japonica). Histological examination of the irradiated cell culture with TUNEL method indicated development of cell death with nuclear DNA fragmentation, which is a typical feature of apoptosis in mammalian cells. The DNA fragments, however, was not detectable in conventional gel electrophoresis. Meanwhile, pulsed-field gel electrophoresis showed high molecular weight DNA fragments, larger than 5 Mb in size. This suggested that the apoptosis-like cell death in plant proceeded without oligonucleosomal DNA cleavage but with large chromatin breaks. The involvement of the apoptosis-like cell death in the radiation damages in plant organs will be also discussed in the presentation.
