Mutant

About: Mutant is a research topic. Over the lifetime, 74520 publications have been published within this topic receiving 3477079 citations.

Agrobacterium tumefaciens mutants affected in crown gall tumorigenesis and octopine catabolism.

Abstract: Mutants of Agrobacterium tumefaciens which affect virulence or the ability to catabolize octopine were isolated after Tn5-induced mutagenesis. Of 8,900 colonies tested, 7 mutants with Tn5 insertions in a specific region of other Ti plasmid unable to catabolize octopine were isolated. Thirty-seven mutants affected in tumorigenesis resulted from insertions in the Ti plasmid and the Agrobacterium chromosome. Of these mutations, 12 were chromosomal and 25 mapped on the plasmid. Twenty-three mapped within a 20-megadalton region, which is distinct from the Ti plasmid sequences found stably integrated into the plant cell genome T-deoxyribonucleic acid). Included in these were mutants that were either a virulent or produced tumors with unusual morphologies. Three mutants contained insertions in the T-deoxyribonucleic acid. These three mutants incited tumors which synthesized octopine but had an altered morphology due to either extensive proliferation of shoots or roots from the tumor callus. Three additional mutants not caused by Tn5 contained mutations in the Ti plasmid.

White collar-1, a central regulator of blue light responses in Neurospora, is a zinc finger protein.

Abstract: The Neurospora crassa blind mutant white collar-1 (wc-1) is pleiotropically defective in all blue light-induced phenomena, establishing a role for the wc-1 gene product in the signal transduction pathway. We report the cloning of the wc-1 gene isolated by chromosome walking and mutant complementation. The elucidation of the wc-1 gene product provides a key piece of the blue light signal transduction puzzle. The wc-1 gene encodes a 125 kDa protein whose encoded motifs include a single class four, zinc finger DNA binding domain and a glutamine-rich putative transcription activation domain. We demonstrate that the wc-1 zinc finger domain, expressed in Escherichia coli, is able to bind specifically to the promoter of a blue light-regulated gene of Neurospora using an in vitro gel retardation assay. Furthermore, we show that wc-1 gene expression is autoregulated and is transcriptionally induced by blue light irradiation.

The expression of a rab-related gene, rab18, is induced by abscisic acid during the cold acclimation process of Arabidopsis thaliana (L.) Heynh

Abstract: We have isolated a rab-related (responsive to ABA) gene, rab18 from Arabidopsis thaliana. The gene encodes a hydrophilic, glycine-rich protein (18.5 kDa), which contains the conserved serine- and lysine-rich domains characteristic of similar RAB proteins in other plant species. The rab18 mRNA accumulates in plants exposed to low temperature, water stress or exogenous ABA but not in plants subjected to heat shock. This stress-related accumulation of the rab18 mRNA is markedly decreased in the ABA-synthesis mutant aba-1, the ABA-response mutant abi-1 or in wild-type plants treated with the carotenoid synthesis inhibitor, fluridone. Exogenous ABA treatment can induce the rab18 mRNA in the aba-1 mutant but not in the abi-1 mutant. These results provide direct genetic evidence for the ABA-dependent regulation of the rab18 gene in A. thaliana.

Autolysis and Autoaggregation in Pseudomonas aeruginosa Colony Morphology Mutants

Abstract: Two distinctive colony morphologies were noted in a collection of Pseudomonas aeruginosa transposon insertion mutants. One set of mutants formed wrinkled colonies of autoaggregating cells. Suppressor analysis of a subset of these mutants showed that this was due to the action of the regulator WspR and linked this regulator (and the chemosensory pathway to which it belongs) to genes that encode a putative fimbrial adhesin required for biofilm formation. WspR homologs, related in part by a shared GGDEF domain, regulate cell surface factors, including aggregative fimbriae and exopolysaccharides, in diverse bacteria. The second set of distinctive insertion mutants formed colonies that lysed at their center. Strains with the most pronounced lysis overproduced the Pseudomonas quinolone signal (PQS), an extracellular signal that interacts with quorum sensing. Autolysis was suppressed by mutation of genes required for PQS biosynthesis, and in one suppressed mutant, autolysis was restored by addition of synthetic PQS. The mechanism of autolysis may involve activation of the endogenous prophage and phage-related pyocins in the genome of strain PAO1. The fact that PQS levels correlated with autolysis suggests a fine balance in natural populations of P. aeruginosa between survival of the many and persistence of the few.

Isolation and characterization of a herpes simplex virus type 1 mutant containing a deletion within the gene encoding the immediate early polypeptide Vmw110

Abstract: Transfection experiments with plasmids containing immediate early (IE) genes of herpes simplex virus type 1 (HSV-1) have previously demonstrated a role for the IE polypeptide Vmw110 (ICP0) in stimulating expression from plasmid-encoded early gene promoters. To gain further insights into the function of Vmw110 we isolated a deletion mutant specifying a truncated form of the polypeptide which had been shown to be inactive in transfection assays. This mutant, dl1403, contained a 2 kb deletion within both the TRL and IRL copies of the Vmw110 gene, and encoded a polypeptide consisting of the original N-terminal 105 amino acids followed by 56 amino acids specified by a reading frame not used by Vmw110. dl1403 was able to replicate and produce plaques on baby hamster kidney (BHK) cells but the yield of infectious virus was 20- to 100-fold lower than obtained with wild-type HSV-1. Surprisingly, comparison of polypeptide synthesis, DNA replication and DNA encapsidation in cells infected with 5 p.f.u./cell dl1403 or wild-type HSV-1 revealed no significant differences. In addition similar numbers of particles were produced in cells infected with the two viruses, resulting in stocks of dl1403 exhibiting significantly higher particle/p.f.u. ratios. The efficiency of plaquing of dl1403 was greatly reduced in Vero and human foetal lung cells compared with BHK cells, but following infection with 5 p.f.u./cell similar yields of infectious virus were obtained from all three cell lines. Marker rescue experiments verified that the reduced yield of dl1403 in BHK cells was a consequence of the deletion within the Vmw110 gene. The results suggest that the effect of this deletion is manifest primarily at low multiplicities of infection and can be largely overcome by increasing the virus dose.