The type III secretion system of Bradyrhizobium japonicum 110SPC4

摘要

Symbiosis between rhizobia and legumes is initiated by an exchange of signal molecules. Communication starts with flavonoids that are secreted by the host plant via the root system. These flavonoids lead to the activation of the transcriptional regulator NodD, a member of the LysR family. NodD binds to the nod box, a conserved sequence within the promoter of nodulation genes, and initiates their transcription (Schlaman et al. 1998). In Bradyrhizobium japonicum 110, a second regulatory system consisting of the genes nodV and nodW is involved in nod gene regulation (Gottfert et al. 1990; Loh et al. 1997). These genes are indispensable for the infection of several host plants. The Nod proteins catalyze the synthesis of Nod factors, modified lipochito-oligosaccharides, that are secreted by the bacterial cell. These signal molecules induce the first steps of nodule development (Hadri, Bisseling 1998).