Direction of transcription nodF nodD nodA nodB nodL nodE nodC Direction of transcriptio nodl nodM nodJ 寻 Organization of the nod gene cluster on the Sym plasmid of Rhizobium leguminosarum biovar viciae,the species that nodulates peas.The product of nodD controls transcription of other nod genes.The nod boxes are highlighted in red,and the arrows indicate the direction of transcription of nod genes.18 Microbiology, Shanghai Jiao Tong University Organization of the nod gene cluster on the Sym plasmid of Rhizobium leguminosarum biovar viciae, the species that nodulates peas. The product of nodD controls transcription of other nod genes. The nod boxes are highlighted in red, and the arrows indicate the direction of transcription of nod genes