Differential regulation of spo0A transcription in Bacillus subtilis: glucose represses promoter switching at the initiation of sporulation

Abstract

We have shown by Si nuclease mapping with in vivo transcripts that the differential expression of a sporulation-regulatory gene, spoOA, is regulated by switching of two discrete promoters during the initiation of sporulation in Bacillus subtilis; vegetative mRNA was transcribed from an upstream promoter (Pv, vegetative promoter), and sporulation-specific mRNA was transcribed from the other promoter (Ps, sporulation-specific promoter) about 150 bp downstream of the P, promoter. Transcription from the P, promoter was at a low level and shut off at To05. On the other hand, transcription from the P, promoter was strongly induced at To.5 and increased until T2 5. In the presence of 2% glucose, Pv-directed transcription was not shut off and was observed even at T1.5, whereas the induction of Ps-directed transcription was completely repressed. A mutant in which the spoOA gene was transcribed only from the P,s promoter could sporulate normally in the presence of 0.1% glucose but could not sporulate at all in the presence of 2% glucose. In a catabolite-resistant sporulation mutant carrying crsA47 (sigA47), a mutation within the gene encoding rA, normal promoter switching from P, to P.was observed in the presence of 2% glucose. Sporulation in Bacillus subtilis, which responds to nutritional starvation in the environment, proceeds through an ordered series of morphological changes leading from a vegetative cell to a dormant spore. This differential process is recognized as a result of the sequential expression of a set of spo genes, whose mutations arrest the process at characteristic intermediate morphological stages. Recently, a number of spo genes have been cloned, and some functions of their products have been characterized, especially for those defined as sporulation-specific sigma factors (for a review, see reference 19). The functions of many of the other spo gene products, however, are still obscure.The transition from the vegetative to the sporulation phase requires at least seven genes known as spoO, since spoO mutants cannot form an asymmetric septum, which is the first morphological change in the sporulation process. Among these genes, the spoOA gene is thought to play a central role in the initiation of sporulation. First, a spoOA mutant exerts the most-pleiotropic effects on sporulationassociated phenotypes such as antibiotic formation, extracellular protease synthesis, and competence development for transformation (22). Second, the sof-l mutation, a missense mutation in the 12th codon of the spoOA gene, suppresses the sporulation-deficient phenotype of spoOB, spoOE, and spoOF mutants (10). Third, the spoOA gene product shares homology with a group of proteins called receivers, which are elements of prokaryotic two-component signal-transducing systems (24,28), and has been shown to be a phosphoacceptor like the other receiver proteins (21). In addition, we have recently found that sporulation in a spoOA temperature-sensitive mutant could be normally induced by a shift-down of the culture temper-* Correspon...

Bacillus subtilis mutants harbouring a single copy of the rRNA operon exhibit severe defects in growth and sporulation

“…4). In addition, we found that the expression of spo0A from the Ps promoter, which is recognized by the sporulation initiation sigma factor, s H (Chibazakura et al, 1991;Predich et al, 1992), was hardly detected in the D9 rrnO + strain (data not shown). Also, microscopic observations revealed that most of the mutant cells were blocked at the early stages of sporulation, where no obvious asymmetrical septum was found (Fig.…”

A functional Spo0A is required for maximal aprE expression in Bacillus subtilis

“…It is phosphorylated by a complex phosphorelay that includes several components needed to integrate multiple signals [2]. The spoOA gene product regulates negatively the abrB gene [3,4], a repressor of several genes which transcription is initiated during the transition between exponential growth and stationary phase [5]. As a positive effector, Spo0A is indispensable for activating the expression of at least three important stage II genes or operons [6].…”

Broadly heterogeneous activation of the master regulator for sporulation in Bacillus subtilis

“…Thus, the disappearance of AbrB could not be responsible for stimulating 0A synthesis. To further investigate the role of AbrB, we took advantage of the fact that spo0A is transcribed both from a vegetative promoter (P v ) responsible for 0A synthesis during growth (recognized by σ A ) and a σ H -dependent promoter (P s ) required for sporulation (11). As expected, in a mutant lacking P v , little or no 0A was present during growth, and, as a consequence, AbrB was at higher than normal levels at hour 0 and remained at high levels even at hour 2.…”