The genes required for the pathogenicity of plant pathogens can be divided into two groups: those for eliciting virulence and those for establishing host-parasite interactions. Basically, the former genes are required for efficient production of the virulence factor(s) leading to the development of symptoms, while the latter genes are needed for well-balanced production of the factors required at each step of the parasitism. To understand the overall picture of plant pathogenicity, we need to understand not only the list of both genes but also how their expressions are regulated. We chose the major virulence genes of soft rot causing Enterobacteriaceae (represented by Pectobacterium carotovorum subsp. carotovorum and Dickeya dadantii) as a model system for dynamic study of the former genes. For the dynamic study of the latter genes, we chose the hrp genes, many of which are responsible for the Type III secretion system (T3SS) and the genes for the T3SS-dependent effectors of xanthomonads. Particularly since the major effector of xanthomonads, the AvrBs3 group or TAL (transcription activator-like) effectors contain NLS (nuclear localization signal) and an acidic activation domain, their studies are also expected to lead us to dynamic analyses of plant genes too.