Cloning and characterization of spoVR, a gene from Bacillus subtilis involved in spore cortex formation

Screening for sigma E-dependent promoters led to the isolation of a gene from Bacillus subtilis, designated spoVR, which appears to be involved in spore cortex formation. Cultures of strains carrying mutations in spoVR had an increased proportion of phase-dark spores, which correlated with an increased proportion of cortexless spores seen by electron microscopy. The numbers of heat- and chloroform-resistant phase-bright spores produced by these mutants were decreased by about 3- to 10-fold, and accumulation of dipicolinate was decreased by more than 3-fold. The spoVR gene was located on the B. subtilis chromosome immediately upstream from, and in the opposite orientation of, the phoAIV gene. Expression of spoVR was initiated at the second hour of sporulation from a sigma E-dependent promoter, and this expression did not require any of the other known mother-cell-specific transcriptional regulators. The spoVR gene was predicted to encode a product of 468 residues.