Trapping and characterization of cold-responsive genes from T-DNA tagging lines in rice

To identify low-temperature-responsive genes in rice, we screened gus-trapped T-DNA tagging lines that had been subjected to cold stress at 5 °C. Out of 15,586 lines, 81 (0.52%) showed cold-responsive GUS activity. Among the 62 lines we selected for further study, 53 showed increased GUS activity while 9 showed less. In addition, 16 of those 62 lines were influenced by abscisic acid (ABA), suggesting an ABA-dependent cold response. We used inverse PCR or thermal asymmetric interlaced (TAIL) PCR to identify 37 tagged genes from those lines, and further characterized two of them at the molecular level. The OsRLK1 gene, which encodes a putative leucine rich repeat (LRR)-type receptor-like protein kinase, was inducible by cold and salt stresses. The OsDMKT1 gene, encoding a putative demethylmenaquinone methyltransferase (DMKT), was also inducible by low temperatures, but not by high salt or drought. The T-DNA-tagged OsDMKT1 gene also co-segregated with the cold-inducible gus gene. Our results indicate that the T-DNA tagging lines are useful in obtaining the stress-responsive genes in rice.