| Abstract: | 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 (Oryza saliva L. cv. IR 72) detected by Agrobacterium vir : :lacZ. fusion genes. The induction was similar to that observed with 5 μm actosyringone (AS). Based on the comprehensive analysis of the data by UV, IR, NMR, MS, HMQC and HMBC, the structures of these two signal factors are identified as 5, 7, 4'-trihydroxy-3', 5'-dimethoxy-flavone (named tricin) and 5, 4' -dihydroxy-3', 5' -dimethoxy-7- (β-D-glucosyloxy) -flavone, respectively. These results demonstrate that monocotyledonous plants do contain highly efficient vir gene inducing factors of Agrobacterium, and the reason why monocotyledonous plants are difficult to transform by Ayrobacterium is not due to absence of vir gene inducing factors, but due to the signal factors only produced in specific stage and tissue of monocotyledonous plants |
