Unique DNA repair property of an ultraviolet-sensitive (radC) mutant of Dictyostelium discoideum

LC_Glucose-Inhibited Division Protein Is Required for Motility, Biofilm Formation, and Stress Response in Lysobacter capsici X2-3

Glucose-inhibited division protein (GidA) plays a critical role in the growth, stress response, and virulence of bacteria. However, how gidA may affect plant growth-promoting bacteria (PGPB) is still not clear. Our study aimed to describe the regulatory function of the gidA gene in Lysobacter capsici, which produces a variety of lytic enzymes and novel antibiotics. Here, we generated an LC_GidA mutant, MT16, and an LC_GidA complemented strain, Com-16, by plasmid integration. The deletion of LC_GidA resulted in an attenuation of the bacterial growth rate, motility, and biofilm formation of L. capsici. Root colonization assays demonstrated that the LC_GidA mutant showed reduced colonization of wheat roots. In addition, disruption of LC_GidA showed a clear diminution of survival in the presence of high temperature, high salt, and different pH conditions. The downregulated expression of genes related to DNA replication, cell division, motility, and biofilm formation was further validated by real-time quantitative PCR (RT–qPCR). Together, understanding the regulatory function of GidA is helpful for improving the biocontrol of crop diseases and has strong potential for biological applications.

Global analysis of transcription kinetics during competence development in Streptococcus pneumoniae using high density DNA arrays

The kinetics of global changes in transcription patterns during competence development in Streptococcus pneumoniae was analysed with high-density arrays. Four thousand three hundred and one clones of a S. pneumoniae library, covering almost the entire genome, were amplified by PCR and gridded at high density onto nylon membranes. Competence was induced by the addition of CSP (competence stimulating peptide) to S. pneumoniae cultures grown to the early exponential phase. RNA was extracted from samples at 5 min intervals (for a period of 30 min) after the addition of CSP. Radiolabelled cDNA was generated from isolated total RNA by random priming and the probes were hybridized to identical high density arrays. Genes whose transcription was induced or repressed during competence were identified. Most of the genes previously known to be competence induced were detected together with several novel genes that all displayed the characteristic transient kinetics of competence-induced genes. Among the newly identified genes many have suggested functions compatible with roles in genetic transformation. Some of them may represent new members of the early or late competence regulons showing competence specific consensus sequences in their promoter regions. Northern experiments and mutational analysis were used to confirm some of the results.

Differential developmental expression of the rep B and rep D xeroderma pigmentosum related DNA helicase genes from Dictyostelium discoideum

DNA helicases are essential to many cellular processes including recombination, replication and transcription, and some helicases function in multiple processes. The helicases encoded by the Xeroderma pigmentosum (XP) B and D genes function in both nucleotide excision repair and transcription initiation. Mutations that affect the repair function of these proteins result in XP while mutations affecting transcription result in neurological and developmental abnormalities, although the underlying molecular and cellular basis for these phenotypes is not well understood. To better understand the developmental roles of these genes, we have now identified and characterized the rep B and rep D genes from the cellular slime mold Dictyostelium discoideum . Both genes encode DNA helicases of the SF2 superfamily of helicases. The rep D gene contains no introns and the rep B gene contains only one intron, which makes their genomic structures dramatically different from the corresponding genes in mammals and fish. However the predicted Dictyostelium proteins share high homology with the human XPB and XPD proteins. The single copy of the rep B and D genes map to chromosomes 3 and 1, respectively. The expression of rep B and D (and the previously isolated rep E) genes during multicellular development was examined, and it was determined that each rep gene has a unique pattern of expression, consistent with the idea that they have specific roles in development. The pattern and extent of expression of these genes was not affected by the growth history of the cells, implying that the expression of these genes is tightly regulated by the developmental program. The expression of the rep genes is a very early step in development and may well represent a key event in the initiation of development in this organism.