Molecular characterization of the virulence gene virA of the Agrobacterium tumefaciens octopine Ti plasmid

The virulence loci play an essential role in tumor formation by Agrobacterium tumefaciens. Induction of vir gene expression by plant signal molecules is solely dependent on the virulence loci virA and virG. This study focused on the virA locus of the octopine type Ti plasmid pTi15955. The nucleic acid sequence of a 5.7-kilobase fragment encompassing virA was determined. Genetic analysis of this region revealed that virA contains one open reading frame coding for a protein of 91 639 daltons. Immunodetection with antibodies raised against a 35-kDa VirA fusion protein produced in E. coli identified the VirA product in wild-type Agrobacterium cells. Moreover, it is shown that the VirA protein is located in the cytoplasmic membrane fraction of Agrobacterium. These data confirm the proposed regulatory function of VirA whereby VirA acts as a membrane sensor protein to identify plant signal molecules in the environment. The proposed sensory function of VirA strikingly resembles the function of the chemotaxis receptor proteins of E. coli.     

The Agrobacterium tumefaciens T-DNA gene 6b is an onc gene

In this article it is shown that the T-DNA of Agrobacterium tumefaciens contains besides the well-known cyt and aux genes another gene with an oncogenic effect in plants. The gene in question is called 6^b and causes the formation of small tumors in plant species such as Nicotiana glauca and Kalanchoe tubiflora.     

Expression of the Escherichia coli glutamate dehydrogenase gene in the cyanobacterium Synechococcus PCC6301 causes ammonium tolerance

The unicellular cyanobacterium Synechococcus PCC6301 lacks a hybridisable homologue of the strongly conserved gdhA gene of E. coli that encodes NADP-specific glutamate dehydrogenase. This is consistent with the failure to find this enzyme in extracts of the cyanobacterium. The E. coli gdhA gene was transferred to Synechococcus PCC6301 by transformation with an integrative vector. High levels of glutamate dehydrogenase activity, similar to those found in ammonium grown E. coli cells, were found in these transformants. These transformed cyanobacteria displayed an ammonium tolerant phenotype, consistent with the action of their acquired glutamate dehydrogenase activity as an ammonium detoxification mechanism. Minor differences in colony size and in growth at low light intensity were also observed.     

Nematode Mitochondrial DNA: Anomalies and Applications

The mitochondrial genome of animal cells is currently under intense investigation by molecular, evolutionary, and population biologists. This review summarizes the available information on the molecular biology of nematode mitochondrial DNA and explains how the fundamental knowledge obtained from these basic studies may be applied to nematode systematics, evolution, and diagnostics.     

Molecular evolution among someDrosophila species groups as indicated by two-dimensional electrophoresis

Summary The evolutionary and phylogenetic relationships of sevenDrosophila species groups (represented byD. melanogaster, D. mulleri, D. mercatorum, D. robusta, D. virilis, D. immigrans, D. funebris, andD. melanica) were investigated by the use of two-dimensional electrophoresis. The resulting phylogeny is congruent with the current views of evolution among these groups based on morphological characters and immunological distances. Previous studies indicated that the ability of one-dimensional electrophoresis to resolve relationships between distantly related taxa extended to about the Miocene [25 million years (Myr) ago], but the present study demonstrates that two-dimensional electrophoresis is a useful indicator of phylogeny even back to the Paleocene (65 Myr ago). In addition, two-dimensional electrophoresis is shown to be a useful technique for detecting slowly evolving structural proteins such as actins and tropomyosins.