A database search for tofM revealed that tofM homologs are conserved in many Burkholderia spp. (Table 2.3 and Figure 2.9), suggesting the importance of their functions for ecological fitness. B. gladioli, which also causes BPB of rice, possesses
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two tofM homologs along with two sets of luxI and luxR homologs. Between the two predicted proteins encoded by the tofM homologs of B. gladioli, one shows the highest level of homology (80% amino acid sequence identity) to TofM, while the other shows only 23.7% identity (Table 2.3). It is noteworthy that, among the tofM homologs investigated in this study, all of the homologs with greater than 49% identity in deduced amino acid sequence to tofM had the same position and orientation patterns as tofM and rsaM relative to their neighboring luxI and luxR homologs (Table 2.3 and Figure 2.9). Regarding the conserved genetic locations and amino acid sequences of encoded proteins, it is very probable that the tofM homologs of other Burkholderia spp., including the select agents, B. mallei and B. pseudomallei, execute similar functions to tofM. Thus, elucidation of the tofM function in the TofI/TofR QS system of B. glumae would provide useful insights into the counter parts of human and animal pathogenic Burkholderia spp.