V. Oke et R. Losick, MULTILEVEL REGULATION OF THE SPORULATION TRANSCRIPTION FACTOR SIGMA(K) IN BACILLUS-SUBTILIS, Journal of bacteriology, 175(22), 1993, pp. 7341-7347
Gene expression in the mother-cell compartment of the Bacillus subtili
s sporangium is governed in part by the sporulation transcription fact
or sigma(K). The production of sigma(K) is controlled at three levels:
by a chromosomal rearrangement that generates the sigma(K)-coding seq
uence (sigK), by compartment-specific transcription of sigK, and by co
nversion of the inactive pro-protein product of sigK (pro-sigma(K)) to
sigma(K). To investigate the function of these multiple levels of reg
ulation, we constructed a set of strains that bypass the chromosomal r
earrangement, pro-protein processing, or both levels of control. Here
we show that one of the functions of the chromosomal rearrangement and
pro-protein processing is to prevent inappropriate production of sigm
a(K) under nonsporulation conditions. In the absence of both of these
levels of control, a low level of sigma(K)-directed gene expression is
observed during stationary phase after growth in rich medium. The app
earance of sigma(K) under these conditions is probably due to a low le
vel of sigma(K)-directed transcription from the sigK promoter in a pos
itive feedback loop. We also report the construction of a strain that
produces high levels of sigma(K) during growth. Using this strain, we
demonstrate that the production of sigma(K) during growth is sufficien
t to induce a cascade of gene expression that closely mimics late even
ts in the mother-cell line of gene expression.