| Research Abstract |
Initiation of sporulation in Bacillus subtilis is controlled by spo0A, B, E, F, H, J and K genes. Among them, 0A has been seemed to be the most important gene because of its pleiotropic effects. Moreover, a suppressor mutation, sof-1, which recovered the sporulation of 0B, 0E and 0F mutants, was known to be an allele of spo0A; it implied that the altered 0A product alone could promote the sporulation in the absence of 0B, 0E and 0F products In the present studies, we determined the spo0A, 0B and 0F prorulation by weights as 29700, 24000, and 14229, respectively. Inhibition of sporulation by high copy 0F was also studied. It is of particular interest that the N terminal amino acid sequences of 0A and 0F products exhibited more than 50% homology. Since they are highly homologous also with Escherichia coli ompR and dye, it is probable that 0A and 0F products are transcription controlling factor responding to exogenous stimulations.
To examine the expression regulation of spo0A and 0F genes, we constructed 0A- or 0F-lacZ fusions; i.e. upstream sequences of 0A and 0F genes involving short N terminal sequences were fused in frame with the coding region of E.coli lacZ. The 0A-lacZ fusion expressed at a low level in the exponential growth phase culture. The expression was highly activated at the end of exponential growth, T0,and reached a plateau at T1. On the other hand, the expression of 0F-lacZ sharply rised up at T1 and the 0F product appeared to substitute the 0A product after T1. The T0 activation of 0A-lacZ expression required the functions of 0B, 0E, 0F and 0H products.
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