Abstract
We reported that expression of SAMDC gene, which has a central role in spermidine (Spd) and spermine (Spm) biosynthesis, is increased by low-temperature stress (5 degree C) in young rice plants. In this work we examined whether increase in Spd and Spm is induced by cold or other abiotic stresses. We found that moderate low-temperature (12 degree C) and submergence stresses other than low-temperature stress induce increase in putrescine (Put) in leaves and stems. We also found that ABA induces increase in Put in roots, while ABA does not induce increase in Put in leaves and stems. These evidences indicates that ABA is unlikely to be directly involved in increase in Put induced by moderate low-temperature and submergence stresses in leaves and stems. The results of expression analysis of arginine decarboxylase and ornithine decaboxylase genes, which are responsible for biosynthesis of Put, are also discussed in relation to stress conditions.
