NHEJ enzymes LigD and Ku participate in stationary-phase mutagenesis in Pseudomonas putida.
Under growth-restricting conditions bacterial populations can rapidly evolve by a process known as stationary-phase mutagenesis. Bacterial nonhomologous end-joining (NHEJ) system which consists of the DNA-end-binding enzyme Ku and the multifunctional DNA ligase LigD has been shown to be important for survival of bacteria especially during quiescent states, such as late stationary-phase populations or sporulation. In this study we provide genetic evidence that NHEJ enzymes participate in stationary-phase mutagenesis in a population of carbon-starved Pseudomonas putida. Both the absence of LigD or Ku resulted in characteristic spectra of stationary-phase mutations that differed from each other and also from the wild-type spectrum. This indicates that LigD and Ku may participate also in mutagenic pathways that are independent from each other. Our results also imply that both phosphoesterase (PE) and polymerase (POL) domains of the LigD protein are involved in the occurrence of mutations in starving P. putida. The participation of both Ku and LigD in the occurrence of stationary-phase mutations was further supported by the results of the analysis of mutation spectra in stationary-phase sigma factor RpoS-minus background. The spectra of mutations identified in the RpoS-minus background were also distinct if LigD or Ku was absent. Interestingly, the effects of the presence of these enzymes on the frequency of occurrence of certain types of mutations were different or even opposite in the RpoS-proficient and deficient backgrounds. These results imply that RpoS affects performance of mutagenic pathways in starving P. putida that utilize LigD and/or Ku.
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia.
Ülvi
Ü
Paris
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia.
Katren
K
Mikkel
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia.
Kairi
K
Tavita
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia.
Signe
S
Saumaa
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia.
Riho
R
Teras
Department of Genetics, Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, 51010 Tartu, Estonia. Electronic address: maia.kivisaar@ut.ee.
Maia
M
Kivisaar
D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D059766:DNA End-Joining Repair; D011088:DNA Ligases / Q000235:genetics* / Q000378:metabolism; D016296:Mutagenesis; D009154:Mutation; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria; D011088:DNA Ligases
Bacterial non-homologous end joining; Ku; LigD; Pseudomonas putida; RpoS; Stationary-phase mutations