[Clinical features of mental disorders in amyotrophic lateral sclerosis]. / Klinicheskie osobennosti psikhicheskikh narushenii pri bokovom amiotroficheskom skleroze.

OBJECTIVE: To investigate the clinical features of associated mental disorders in amyotrophic lateral sclerosis (ALS). MATERIAL AND METHODS: Twenty-seven patients (9 men and 18 women, mean age 59.8±11.9 years) with the upper and lower motor neuron lesions were studied. The average duration of the disease at the time of examination was 3.2±2.4 years. Clinical psychopathological and follow-up methods were used. The severity of cognitive impairment was measured with the Edinburgh Cognitive and Behavioral ALS Screen (ECAS). The Montgomery-Asberg Depression Rating Scale (MADRS) was used to assess the severity of depression. RESULTS: Most patients (88.9%) had cognitive impairments. Amnestic disorders were primarily presented by hypo- and dysmnesia. These patients showed slow thinking, torpidity combined with circumstantiality and a tendency to detail. In addition to attentional fluctuations, we observed reduced attentional capacity, higher distractibility, and difficulty concentrating. The later stages of the disease were accompanied by the overall decline of thinking ability and intelligence with severe perseverations, and failure in the adequate self-assessment. More than half of the patients also developed the symptoms, such as dynamic aphasia, as well as functional speech disorders, i.e. gnosis and praxis. The vast majority of the patients had affective disorders (92.3%). So far as the symptoms of the underlying neurological condition worsened, the associated depressive symptoms prevailed (62.9%). Particular attention should be given to the clinical cases of ALS associated with psychotic disorders such as acute schizophrenia-like psychotic disorders. CONCLUSION: Presence of affective, cognitive and behavioral disorders, as well as a specific neuroimaging pattern, are considered as a whole as the manifestation of the behavioral variant of frontotemporal dementia (FTD). This provides support for the current opinion suggesting the similarity of ALS and FTD, which allows for considering these diseases as different phenotypic manifestations of a single pathological process.

Molecular evolution of virulence in natural field strains of Xanthomonas campestris pv. vesicatoria.

The avrBs2 avirulence gene of the bacterial plant pathogen Xanthomonas campestris pv. vesicatoria triggers disease resistance in pepper plants containing the Bs2 resistance gene and contributes to bacterial virulence on susceptible host plants. We studied the effects of the pepper Bs2 gene on the evolution of avrBs2 by characterizing the molecular basis for virulence of 20 X. campestris pv. vesicatoria field strains that were isolated from disease spots on previously resistant Bs2 pepper plants. All field strains tested were complemented by a wild-type copy of avrBs2 in their ability to trigger disease resistance on Bs2 plants. DNA sequencing revealed four mutant alleles of avrBs2, two of which consisted of insertions or deletions of 5 nucleotides in a repetitive region of avrBs2. The other two avrBs2 alleles were characterized by point mutations with resulting single amino acid changes (R403P or A410D). We generated isogenic X. campestris pv. vesicatoria strains by chromosomal avrBs2 gene exchange to study the effects of these mutations on the dual functions of avrBs2 in enhancing bacterial virulence and inducing plant resistance by in planta bacterial growth experiments. The deletion of 5 nucleotides led to loss of avrBs2-induced resistance on Bs2 pepper plants and abolition of avrBs2-mediated enhancement of fitness on susceptible plants. Significantly, the point mutations led to minimal reduction in virulence function of avrBs2 on susceptible pepper plants, with either minimal (R403P allele) or an intermediate level of (A410D allele) triggering of resistance on Bs2 plants. Consistent with the divergent selection pressures on avrBs2 exerted by the Bs2 resistance gene, our results show that avrBs2 is evolving to decrease detection by the Bs2 gene while at the same time maintaining its virulence function.

Molecular signals required for type III secretion and translocation of the Xanthomonas campestris AvrBs2 protein to pepper plants.

Strains of Xanthomonas campestris pv. vesicatoria (Xcv) carrying avrBs2 are specifically recognized by Bs2 pepper plants, resulting in localized cell death and plant resistance. Agrobacterium-mediated transient expression of the Xcv avrBs2 gene in plant cells results in Bs2-dependent cell death, indicating that the AvrBs2 protein alone is sufficient for the activation of disease resistance-mediated cell death in planta. We now provide evidence that AvrBs2 is secreted from Xcv and that secretion is type III (hrp) dependent. N- and C-terminal deletion analysis of AvrBs2 has identified the effector domain of AvrBs2 recognized by Bs2 pepper plants. By using a truncated Pseudomonas syringae AvrRpt2 effector reporter devoid of type III signal sequences, we have localized the minimal region of AvrBs2 required for type III secretion in Xcv. Furthermore, we have identified the region of AvrBs2 required for both type III secretion and translocation to host plants. The mapping of AvrBs2 sequences sufficient for type III delivery also revealed the presence of a potential mRNA secretion signal.

Genetic and environmental factors affecting T-pilin export and T-pilus biogenesis in relation to flagellation of Agrobacterium tumefaciens.

The T pilus, primarily composed of cyclic T-pilin subunits, is essential for the transmission of the Ti-plasmid T-DNA from Agrobacterium tumefaciens to plant cells. Although the virB2 gene of the 11-gene virB operon was previously demonstrated to encode the full-length propilin, and other genes of this operon have been implicated as members of a conserved transmembrane transport apparatus, the role of each virB gene in T-pilin synthesis and transport and T-pilus biogenesis remained undefined. In the present study, each virB gene was examined and was found to be unessential for T-pilin biosynthesis, except virB2, but was determined to be essential for the export of the T-pilin subunits and for T-pilus formation. We also find that the genes of the virD operon are neither involved in T-pilin export nor T-pilus formation. Critical analysis of three different virD4 mutants also showed that they are not involved in T-pilus biogenesis irrespective of the A. tumefaciens strains used. With respect to the environmental effects on T-pilus biogenesis, we find that T pili are produced both on agar and in liquid culture and are produced at one end of the A. tumefaciens rod-shaped cell in a polar manner. We also report a novel phenomenon whereby flagellum production is shut down under conditions which turn on T-pilus formation. These conditions are the usual induction with acetosyringone at pH 5.5 of Ti-plasmid vir genes. A search of the vir genes involved in controlling this biphasic reaction in induced A. tumefaciens cells revealed that virA on the Ti plasmid is involved and that neither virB nor virD genes are needed for this reaction. The biphasic reaction therefore appears to be mediated through a two-component signal transducing system likely involving an unidentified vir gene in A. tumefaciens.

Characterization of flagella genes of Agrobacterium tumefaciens, and the effect of a bald strain on virulence.

Agrobacterium tumefaciens produces flagella that are arranged circumthecally near one end of the bacilliform cell. The flagella are required for motility to facilitate reaching the root surface, and possibly aid in orientating the bacterial cells at various sites for infection. We have identified three flagella genes designated flaA, flaB, and flaC. Mutations in flaA, flaB and flaC result in abberant swimming behaviour. Electron microscopic examination of these mutants revealed the defective flagella. A non-motile, bald mutant strain was generated by deleting all three fla genes. Nucleotide sequencing of flaA, flaB, and flaC showed that they have a potential coding capacity for polypeptides of 307, 321, and 314 amino acid residues, respectively. The predicted amino acid sequences of the A. tumefaciens FlaA and FlaB proteins are similar (66% average identity) to the FlaA and FlaB proteins encoded by flaA and flaB genes, respectively, in Rhizobium meliloti. There was no counterpart FlaC protein reported in R. meliloti, but the A. tumefaciens FlaC is similar in amino acid sequence to the R. meliloti FlaA (59.8% identity) and FlaB (66.7% identity). Distinct from FlaA and FlaB of R. meliloti is the absence of histidine and cysteine residues and their shorter length (by 88 amino acid residues fewer than FlaA and FlaB of R. meliloti). The transcriptional start sites of each fla gene determined by primer extension revealed consensus-sequence boxes representing potential binding sites for sigma 28 RNA polymerase (RNAP) upstream of the transcriptional start of each fla gene. Besides the potential sigma 28-binding site upstream of flaC, also present are additional putative conserved sequences, GC at -11 and GG at -21 from the transcriptional start, that resemble potential binding motifs for sigma 54. Because the sigma 54 promoter is associated with genes regulated by physiological changes in various bacteria, the flaC gene might be similarly regulated in response to A. tumefaciens responding to host plant stimuli. Virulence studies showed that the bald strain was consistently reduced in virulence below that of the parental wild-type strain by at least 38%. The difference is statistically significant and suggests that the flagella may play a role in facilitating virulence.