Identification of a novel signal for activation of Ti plasmid- encoded vir genes from rice (Oryza sativa L.)

Virulence (vir) genes of Ti plasmids code for a specialized conjugation system that mediates the mobilization and transfer of T-DNA from Agrobacterium to the genome of higher plants. This system is activated by a number of plant-specific phenolics, well characterized in dicots, via a two-component regulatory system. In contrast, little is known about the occurrence of vir-inducing signals in monocots, especially in the cereal crops.We have examined the effects of exudates and extracts from various rice tissues at different