Changes in translatable mRNA populations induced in rice seedlings by exposure to freeze-thaw stress

In order to examine whether changes in gene expression are induced by injury in seedlings of rice (Oryza sativa) after a lethal freeze-thaw stress. mRNAs were extracted and their in vitro translation products were compared with those of the control plants by polyacrylamide gel electrophoresis. An mRNA encoding an entirely new protein with M(r) of ca. 37 kDa was detected as early as 30 min of thawing at 28 degrees C. Two-dimensional gel electrophoresis revealed the induction of mRNAs for at least 10 additional proteins, including those in a range of 15 to 20 kDa. Most of these proteins appear to be distinct from heat-shock proteins. The steady state level of mRNAs encoding putative major light-harvesting chlorophyll a/b binding protein-I and -II were, on the other hand, very low as compared with those of the control plants. The changes observed resemble those previously seen in cold-sensitive plants exposed to sub-lethal chilling temperatures (4-10 degrees C).