Amaranthus caudatus subsp. mantegazzianus: A new host of ‘Candidatus Phytoplasma hispanicum’ (subgroup 16Sr XIII‐A)

In Argentina, amaranth is a promising crop due to high nutritional quality and ability to grow in a diversity of environments. In areas cultivated with amaranth, were observed plants exhibiting slow growth, deformed leaves, proliferation of shoots and malformed lateral panicles. Field survey revealed up to 96% disease incidence and 92% of the seeds collected from mother plants produced diseased seedlings. A phytoplasma was detected in association with seedlings and adult plants using nested PCR assays. Molecular identification by computer‐simulated RFLP and phylogenetic analysis evidenced the occurrence of a ‘Candidatus Phytoplasma hispanicum’‐related strain, affiliated with 16SrXIII‐A subgroup. The findings implicate amaranth as a new host for this subgroup and as a potential reservoir of the pathogen for other cultivated species. In addition, to the best of our knowledge, this study reports for the first time the presence of 16SrXIII‐A phytoplasma in Argentina and in South America. Furthermore, transmission assays pointed that naturally infected seed is an important vehicle of dissemination of the pathogen, threatening the expansion of the crop for new geographical areas.     

Elementary Flux Modes Analysis of Functional Domain Networks Allows a Better Metabolic Pathway Interpretation

Metabolic network analysis is an important step for the functional understanding of biological systems. In these networks, enzymes are made of one or more functional domains often involved in different catalytic activities. Elementary flux mode (EFM) analysis is a method of choice for the topological studies of these enzymatic networks. In this article, we propose to use an EFM approach on networks that encompass available knowledge on structure-function. We introduce a new method that allows to represent the metabolic networks as functional domain networks and provides an application of the algorithm for computing elementary flux modes to analyse them. Any EFM that can be represented using the classical representation can be represented using our functional domain network representation but the fine-grained feature of functional domain networks allows to highlight new connections in EFMs. This methodology is applied to the tricarboxylic acid cycle (TCA cycle) of Bacillus subtilis, and compared to the classical analyses. This new method of analysis of the functional domain network reveals that a specific inhibition on the second domain of the lipoamide dehydrogenase (pdhD) component of pyruvate dehydrogenase complex leads to the loss of all fluxes. Such conclusion was not predictable in the classical approach.     

Retrophosphorylation of Mkk1 and Mkk2 MAPKKs by the Slt2 MAPK in the yeast cell integrity pathway

In Saccharomyces cerevisiae, a variety of stresses and aggressions to the cell wall stimulate the activation of the cell wall integrity MAPK pathway, which triggers the expression of a series of genes important for the maintenance of cell wall homeostasis. This MAPK module lies downstream of the Rho1 small GTPase and protein kinase C Pkc1 and consists of MAPKKK Bck1, MAPKKs Mkk1 and Mkk2, and the Slt2 MAPK. In agreement with previous reports suggesting that Mkk1 and Mkk2 were functionally redundant, we show here that both Mkk1 and Mkk2 alone or even chimerical proteins constructed by interchanging their catalytic and regulatory domains are able to efficiently maintain signal transduction through the pathway. Both Mkk1 and Mkk2 are phosphorylated in vivo concomitant to activation of the cell integrity pathway. Interestingly, hyperphosphorylation of the MEKs required not only the upstream components of the pathway, but also a catalytically competent Slt2 MAPK downstream. Active Slt2 purified from yeast extracts was able to phosphorylate Mkk1 and Mkk2 in vitro. We have mapped Ser(50) as a direct phosphorylation target for Slt2 in Mkk2. However, substitution of all (Ser/Thr)-Pro canonical MAPK target sites with alanine did not totally abrogate Slt2-dependent Mkk2 phosphorylation. Mutation or deletion of a conserved MAPK-docking site at the N-terminal extension of Mkk2 precluded its interaction with Slt2 and negatively affected retrophosphorylation. Our data show that the cell wall integrity MAPKKs are targets for their downstream MAPK, suggesting the existence of complex feedback regulatory mechanisms at this level.     

Guinea pig-adapted foot-and-mouth disease virus with altered receptor recognition can productively infect a natural host

We report that adaptation to infect the guinea pig did not modify the capacity of foot-and-mouth disease virus (FMDV) to kill suckling mice and to cause an acute and transmissible disease in the pig, an important natural host for this pathogen. Adaptive amino acid replacements (I(248)-->T in 2C, Q(44)-->R in 3A, and L(147)-->P in VP1), selected upon serial passages of a type C FMDV isolated from swine (biological clone C-S8c1) in the guinea pig, were maintained after virus multiplication in swine and suckling mice. However, the adaptive replacement L(147)-->P, next to the integrin-binding RGD motif at the GH loop in VP1, abolished growth of the virus in different established cell lines and modified its antigenicity. In contrast, primary bovine thyroid cell cultures could be productively infected by viruses with replacement L(147)-->P, and this infection was inhibited by antibodies to alphavbeta6 and by an FMDV-derived RGD-containing peptide, suggesting that integrin alphavbeta6 may be used as a receptor for these mutants in the animal (porcine, guinea pig, and suckling mice) host. Substitution T(248)-->N in 2C was not detectable in C-S8c1 but was present in a low proportion of the guinea pig-adapted virus. This substitution became rapidly dominant in the viral population after the reintroduction of the guinea pig-adapted virus into pigs. These observations illustrate how the appearance of minority variant viruses in an unnatural host can result in the dominance of these viruses on reinfection of the original host species.     

Use of radioimmunotherapy in stem cell transplantation and posttransplantation: focus on yttrium 90 ibritumomab tiuxetan

Although autologous stem cell transplantation (ASCT) produces prolonged disease-free survival in many patients with non-Hodgkin's lymphoma (NHL), relapse remains the most common cause of treatment failure. Because of the potential benefit of adding targeted irradiation to conditioning regimens, clinical trials are testing the safety and efficacy of combining radioimmunotherapy with yttrium 90 ibritumomab tiuxetan or iodine 131 tositumomab and chemotherapy, either as replacement for total body irradiation or in addition to standard high-dose chemotherapy (HDC) regimens. Current strategies include using standard or escalated doses of radioimmunoconjugates with HDC before ASCT in patients with relapsed or refractory B-cell NHL. We reviewed the safety and efficacy of (90)Y ibritumomab tiuxetan as part of the conditioning regimen before ASCT. Preliminary data from phase 1 and 2 trials show that (90)Y ibritumomab tiuxetan may be safely added to HDC preparative regimens for high-risk B-cell NHL. Additionally, comparisons of outcomes with radioimmunotherapy and ASCT with historical controls suggest that it may be more effective than conventional regimens. Results of (90)Y ibritumomab tiuxetan alone posttransplantation in select patients who have relapsed after HDC and ASCT are also encouraging. Studies of (90)Y ibritumomab tiuxetan in the setting of allogeneic stem cell transplantation appear promising as well.     

Novel Kdr mutations (K964R and A943V) in pyrethroid‐resistant populations of Triatoma mazzottii and Triatoma longipennis from Mexico and detoxifying enzymes

Although having five different ways of transmission the vector-borne is the principal way of transmission of Chagas disease, which involves insects of the subfamily Triatominae (Hemiptera: Reduviidae). Nineteen of the 31 species that occur in Mexico are associated with humans, and all are capable of transmitting the disease. Pyrethroids are the insecticides recommended for the control of these vectors in Mexico. We determined the susceptibility to the pyrethroids dcltamethrin and permethrin of peridomestic populations of Triatoma mazzottii Usinger and two populations of Triatoma longipetmis Usinger in comparison with a reference strain for each species. Bioassays were performed for the determination of the LD50 for both field populations and reference strains. A maximum of 27 fold resistance to deltamethrin was observed in T. mazzottii, meanwhile, for permethrin, T. longipennis from Jalisco show the highest value of 3.19 fold. There was significantly increased activity of esterases in field populations in comparison with their corresponding reference strain. The results of the search of kdr mutations related to the resistance to deltamethrin and permethrin in the evaluated species show the presence of mutations in the field populations, as is the case with individuals of T. mazzottii, for which the mutation was found A943V, and for the two populations of T. longipennis included in this study, we report the presence of the kdr mutation K964R. Evaluation of the various mechanisms involved in resistance to pyrethroids in triatomines from Mexico could guide us to the real justification for insecticide resistance monitoring.