Truncated Spo0A transcription activities in Bacillus subtilis

Sporulation of Bacillus subtilis is an energetically expensive process that requires transcription regulation of a great number of genes. The onset of the process is precisely controlled by signal transduction system called phospho-relay. The final component of the system and the major control element of sporulation initiation is the response regulator Spo0A. This protein consists of an N-terminal phosphoacceptor domain connected to a C-terminal transcription activation domain by a flexible linker. The unphosphorylated N-terminal domain inhibits the ability of the C-terminal domain to bind DNA and to regulate genes transcription. This inhibition is overcome when the N-terminal domain is phosphorylated by phosphorelay. In vitro experiments showed that the C-terminal domain alone is able to bind to DNA and activate transcription. In our study we have investigated the capability of the C-terminal domain to initiate sporulation and to regulate transcription from Spo0A dependent promoters in vivo. The transcription activity of the C-terminal domain was studied using lacZ fusion of spoIIE and abrB promoters, respectively. Our results suggest that although the C-terminal domain is fully trancriptionally active, the cells with such truncated Spo0A protein are not able to complete the sporulation process due to irregularity in timing of Spo0A activation and subsequent deregulation of the entire sporulation pathway.