The Bacillus subtilis glucose starvation-inducible transcription units, gsi4 and gsiB, were characterized by DNA sequencing, transcriptional mapping, mutational analysis, and expression in response to changes in environmental conditions. The gsiA operon was shown to consist of two genes, gsiAA and gsiAB, predicted to encode 44.9-and 4.8-kDa polypeptides, respectively. The gsiB locus contains a single cistron which encodes a prbtein of unusual structure; most of its amino acids are arranged in five highly conserved, tandemly repeated units of 20 amino acids. The 5' ends ofgsiA and gsiB mRNAs were located by primer extension analysis; their locations suggest that both are transcribed by RNA polymerase containing sigma A. Expression of both gsiA and gsiB was induced by starvation for glucose or phosphate or by addition of decoyinine, but only gsi4 was induced by exhaustion of nutrient broth or by amino acid starvation. Regulation ofgsi4 expression was shown to be dependent upon the two-component signal transduction system ComP-ComA, which also controls expression of genetic competence genes. Mutations in mecA bypassed the dependency of gsi4 expression on ComA. Disruption of gsiA relieved glucose repression of sporulation but did not otherwise interfere with sporulation, development of competence, motility, or glucose starvation survival. We propose that gsiA4 and gsiB are members of an adaptive pathway of genes whose products are involved in responses to nutrient deprivation other than sporulation.When available nutrients fall below the levels necessary to sustain rapid vegetative growth of Bacillus subtilis, several developmental programs are initiated. In one program, individual cells undergo a process of morphogenesis that culminates in the differentiation of rod-shaped vegetative cells into spherical, environmentally resistant, dormant cells known as spores. The regulation of this response depends on a number of gene products which appear to be part of a complex, intertwined signal transduction network that controls not only initiation of sporulation but also other programs, such as development of genetic competence, motility and chemotaxis, degradative enzyme synthesis, and antibiotic production. Some of the regulatory genes required for these various adaptive responses are members of the two-component family of bacterial signal transduction systems; others are known to be transcription factors (6,7,13

Two previously identified Bacillus subtilis DNA segments, dciA and dciB, whose transcripts accumulate very rapidly after induction of sporulation, were found in the same 6.2 kb transcription unit, now known as the dciA operon. Analysis of the sequence of the dciA operon showed that its putative products are homologous to bacterial peptide transport systems. The product of the fifth gene, DciAE, is similar to peptide-binding proteins from Escherichia coli and Salmonella typhimurium (DppA and OppA) and B. subtilis (OppA). A null mutation in dciAE abolished the ability of a proline auxotroph to grow in a medium containing the dipeptide Pro-Gly as sole proline source, suggesting that the dciA operon encodes a dipeptide transport system.

Abstract. A ll0-115-kD protein is present at levels 27-fold higher in migratory epithelium in the rat cornea than in stationary epithelium. This protein represents 2.7% of the total protein in migratory epithelium 6-h postabrasion wound and 0.1% of the total protein in stationary epithelium. Our findings demonstrate that this ll0-115-kD protein is vinculin. In Western blots comparing proteins from migratory and control epithelium, antibody against vinculin crossreacted with the ll0-115-kD protein. Using immunoslot blots, vinculin was determined to be present at maximal levels 6 h postabrasion wound, at levels 22-and 8-fold higher than control at 18 and 48 h, respectively, returning to control levels 72 h postwounding. Vinculin was also localized by indirect immunohistochemistry in migrating corneal epithelium. 3-mm scrape wounds were allowed to heal in vivo for 20 h. In fiat mounts of these whole wounded corneas, vinculin was localized as punctate spots in the leading edge of migrating epithelium. In cryostat sections, vinculin was localized as punctate spots along the basal cell membranes of the migrating sheet adjacent to the basement membrane and in patches between cells as well as diffusely throughout the cell. Only very diffuse localization with occasional punctate spots between adjacent superficial cells was present in stationary epithelium. The increased synthesis of vinculin during migration and the localization of vinculin at the leading edge of migratory epithelium suggest that vinculin may be involved in cell-cell and cell-substrate adhesion as the sheet of epithelium migrates to cover a wound.

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