IDENTIFICATION OF RICE (ORYZA-SATIVA L) SIGNAL FACTORS CAPABLE OF INDUCING AGROBACTERIUM VIR GENE-EXPRESSION

Two kinds of signal factors capable of inducing Agrobaorerium vir gene expression were purified and identified from leaf extracts of panicle -differentiating to flowering stage of rice (Orgza sativa L. cv. IR 72 ) detected by Agrobacterium vir::lacZ fusion genes. The induction was similar to that observed with 5 mu m actosyringone (AS). Based on the comprehensive analysis of the data UV, IR, NMR, MS, HMQC and HMBC, the structures of these two signal factors are identified as 5, 7, 4'-tri hydroxy-3', 5'-dimethoxy-flavone (named tricin) and 5, 4'-dihydroxy-3' , 5'-dimethoxy-7-(beta-D-glucosyloxy)-flavone, respectively. These res ults demonstrate that monocotyledonous plants do contain highly effici ent vir gene inducing factors of Agrobacterium, and the reason why mon ocotyledonous plants are difficult to transform by Ayrobacterium is no t due to absence of vir gene inducing factors, but due to the signal f actors only produced in specific stage and tissue of monocotyledonous plants.