FIGURE 4.

Genetic structures, thiamine biosynthetic genes, and possible mechanisms of riboswitch control. The location and mechanism of the E. coli and B. subtilis riboswitches are detailed elsewhere (Mironov et al. 2002; Winkler et al 2002a). The putative TPP riboswitch from P. secunda resides immediately upstream from the poly(A) tail in the cDNA clone of the thiC gene. The putative TPP riboswitch domain in F. oxysporum is located in a 5′-UTR intron of the sti35 gene according to the genomic sequence, but is absent in the cDNA clone.