First Report of HLB Causal Agent in Psyllid in State of Bahia, Brazil

The state of Bahia ranks fourth in the national rank for citrus production, and the region of Chapada Diamantina is emerging an important producer of orange for fresh fruit market. Huanglongbing (HLB) is the major phytosanitary threat to Bahia citriculture. In Brazil, the disease was first reported in 2004 in São Paulo state. The bacterium Candidatus Liberibacter asiaticus (CLas) is one of the causal agents of HLB, which is transmitted by the insect vector Diaphorina citri Kuwayama (Hemiptera: Liviidae). Bahia is a HLB-free area; therefore, it is essential to monitor its citrus-producing areas to early detect any possible introduction of the CLas. This study aimed to monitor the presence of the bacteria in the insect vector. Diaphorina citri samples were collected from 2011 to 2014 in different cities located at Chapada Diamantina region and tested by qPCR for the presence of CLas. Three samples were considered positive to bacterium, and all from psyllids collected on Murraya paniculata in the city of Seabra.

Structural insights revealed by two novel THRB mutations

PURPOSE

Among the inheritable forms of impaired sensitivity to thyroid hormone, resistance to thyroid hormone (RTH) due to mutations in the thyroid hormone receptor beta gene (THRB) is the first and best known described defect, revealing a wide phenotypic variability with an incompletely understood physiopathology. The objective of this study was to evaluate two novel mutations in THRB, N331H and L346R, in an attempt to provide a rational understanding of the harmful effects caused by them.

METHODS

The mutations of two patients with RTHβ were reproduced for analysis of gene transactivation by dual-luciferase reporter assay, and for molecular modeling for crystallography-based structural assessment. Serum measurements of TSH and FT4 were performed to compare the thyrotrophic resistance to thyroid hormone between RTHβ patients and controls.

RESULTS

Both mutants showed impaired gene transactivation, with greater damage in L346R. Molecular modeling suggested that the damage occurring in N331H is primarily due to reduced strength of the hydrogen bonds that stabilize T3 in its ligand-binding cavity (LBC), whereas in L346R, the damage is more marked and is mainly due to changes in hydrophobicity and molecular volume inside the LBC. Hormonal dosages indicated that the L346R mutant exhibited greater thyrotrophic resistance than N331H.

CONCLUSIONS

This study provides a rational understanding of the effects of mutations, indicating deleterious structural changes in the LBC in both THR, and discloses that not only the position of the mutation but, notably, the nature of the amino acid exchange, has a cardinal role in the functional damage of the receptor.

Association Between Citrus Flushing Cycles and Asian Citrus Psyllid Demography in Huanglongbing-Free Area in Brazil

Diaphorina citri Kuwayama (Hemiptera: Liviidae), named as Asian citrus psyllid (ACP), is the vector of the bacterium associated with huanglongbing (HLB), the most destructive citrus disease. The use of citrus flushing and ACP monitoring tools is essential for the knowledge of the occurrence pattern of cycles of both and for the improvement of the ACP management. During 3 years, 20 branches from 20 trees were evaluated for vegetative flushing, ACP abundance, and occupation in tree and branches in a Brazilian citrus area free for HLB. The obtained data was investigated through spectral and co-spectral analyses. Four to 12 flush shoot cycles occurred per year, which were similar to abundance and occupation cycles of ACP, with an apparent synchronization between these variables. In general, there was a difference from 14 to 19 days between flushing and ACP peaks, with an occurrence of the flushing peaks before the ACP peaks. Results will provide useful information to citrus growers and agricultural defense agencies to apply a suitable and targeted ACP management, which will avoid or delay the disease entrance into still free HLB areas. In addition, the modeling of occupation and abundance cycles of vectors as applied in this study may be useful for other pathosystems which insect vectors are associated or even in the intrusion monitoring programs.

Thermodynamic analysis of interactions of the Hsp90 with adenosine nucleotides: A comparative perspective

Hsp90s are key proteins in cellular homeostasis since they interact with many client proteins. Several studies indicated that Hsp90s are potential targets for treating diseases, such as cancer or malaria. It has been shown that Hsp90s from different organisms have peculiarities despite their high sequence identity. Therefore, a detailed comparative analysis of several Hsp90 proteins is relevant to the overall understanding of their activity. Accordingly, the goal of this work was to evaluate the interaction of either ADP or ATP with recombinant Hsp90s from different organisms (human α and β isoforms, Plasmodium falciparum, Leishmania braziliensis, yeast and sugarcane) by isothermal titration calorimetry. The measured thermodynamic signatures of those interactions indicated that despite the high identity among all Hsp90s, they have specific thermodynamic characteristics. Specifically, the interactions with ADP are driven by enthalpy but are opposed by entropy, whereas the interaction with ATP is driven by both enthalpy and entropy. Complimentary structural and molecular dynamics studies suggested that specific interactions with ADP that differ from those with ATP may contribute to the observed enthalpies and entropies. Altogether, the data suggest that selective inhibition may be more easily achieved using analogues of the Hsp90-ADP bound state than those of Hsp90-ATP bound state.

Titanium-released from dental implant enhances pre-osteoblast adhesion by ROS modulating crucial intracellular pathways

It is important to understand the cellular and molecular events that occur at the cell-material interface of implants used for bone repair. The mechanisms involved in the initial stages of osteoblast interactions with the surface of the implant material must be decisive for cell fating surrounding them. In order to address this issue, we decided to investigate if conditioned medium for dental implants was able to modulate murine pre-osteoblast metabolism. First, we determined the concentration of titanium (Ti)-containing conditioned medium and found that it was 2-fold increased (p < 0.0001). We have reported that this conditioned medium significantly up-modulated pre-osteoblast adhesion up to 24 h (p < 0.0001). In parallel, our results showed that both phosphorylations of FAK (focal adhesion kinase) at Y397 (p < 0.0011) and Cofilin at Ser03 (p < 0.0053) were also up-modulated, as well as for Rac1 expression (p < 0.0175); both of them are involved with cell adaptation by rearranging cytoskeleton actin filaments. Thereafter, Ti-containing medium stimulated ROS (reactive oxygen species) production by pre-osteoblast cells, and it is very possible that ROS compromised PTP-1B (protein tyrosine phosphatase 1B) activation since PTP1B was down-phosphorylated (p < 0.0148). The low PTP activity guarantees the phosphorylation of FAK at Y-residue, causing better pre-osteoblast adhesion in response to Ti-containing medium. Altogether, these data indicate that ROS indirectly modulate FAK phosphorylation in response to Ti-released from dental implants. Taken the results in account, these data showed for the first time that the implanted dental device is able to dynamically affect surrounding tissues, mainly by promoting a better performance of the pre-osteoblast cells. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2968-2976, 2017.

Identification of a new hormone-binding site on the surface of thyroid hormone receptor

Thyroid hormone receptors (TRs) are members of the nuclear receptor superfamily of ligand-activated transcription factors involved in cell differentiation, growth, and homeostasis. Although X-ray structures of many nuclear receptor ligand-binding domains (LBDs) reveal that the ligand binds within the hydrophobic core of the ligand-binding pocket, a few studies suggest the possibility of ligands binding to other sites. Here, we report a new x-ray crystallographic structure of TR-LBD that shows a second binding site for T3 and T4 located between H9, H10, and H11 of the TRα LBD surface. Statistical multiple sequence analysis, site-directed mutagenesis, and cell transactivation assays indicate that residues of the second binding site could be important for the TR function. We also conducted molecular dynamics simulations to investigate ligand mobility and ligand-protein interaction for T3 and T4 bound to this new TR surface-binding site. Extensive molecular dynamics simulations designed to compute ligand-protein dissociation constant indicate that the binding affinities to this surface site are of the order of the plasma and intracellular concentrations of the thyroid hormones, suggesting that ligands may bind to this new binding site under physiological conditions. Therefore, the second binding site could be useful as a new target site for drug design and could modulate selectively TR functions.

Crystallization and preliminary X-ray diffraction analysis of human IL-22 bound to its soluble decoy receptor IL-22BP

Interleukin-22 (IL-22) is a pleiotropic cytokine that is involved in inflammatory responses. Human IL-22 was incubated with its soluble decoy receptor IL-22BP (IL-22 binding protein) and the IL-22-IL-22BP complex was crystallized in hanging drops using the vapour-diffusion method. Suitable crystals were obtained from polyethylene glycol solutions and diffraction data were collected to 2.75 A resolution. The crystal belonged to the tetragonal space group P4(1), with unit-cell parameters a = b = 67.9, c = 172.5 A, and contained two IL-22-IL-22BP complexes per asymmetric unit.

Strain characterization of Candida parapsilosis fungemia by molecular typing methods

The present study used two molecular typing methods to investigate a cluster of eight cases of Candida parapsilosis fungemia in a hospital in Rio de Janeiro, Brazil. Candida parapsilosis is an important opportunistic pathogen that is frequently involved in outbreaks of nosocomial fungemia. Identification of a common source of infection and determination of genetic relatedness among the strains involved in outbreaks are important for infection control. Candida parapsilosis strains were isolated from the bloodstream of patients housed in an intensive-care unit (n=5) and in individual rooms (n=3). An additional strain of Candida parapsilosis was isolated from a hyperalimentation infusion flask, which was implicated by molecular typing to be the source of infection. All strains were identified using morphological and biochemical methods. The genetic relationship between patients' strains and the hyperalimentation infusion strain was assessed by electrophoretic karyotype (EK) analysis and random amplification of polymorphic DNA (RAPD). Both methods resulted in patterns that allowed differentiation of the isolates. Candida parapsilosis fungemia, in three of the eight patients, resulted from a common source of infection, as demonstrated by molecular typing methods. Image analysis of EK patterns indicated that these strains were closest to Candida parapsilosis Group II, a grouping that is a less frequent clinical isolate than the major Group I strains.