Significant performance enhancement of InGaN/GaN nanorod LEDs with multi-layer graphene transparent electrodes by alumina surface passivation

Nanotextured surfaces provide an ideal platform for efficiently capturing and emitting light. However, the increased surface area in combination with surface defects induced by nanostructuring e.g. using reactive ion etching (RIE) negatively affects the device's active region and, thus, drastically decreases device performance. In this work, the influence of structural defects and surface states on the optical and electrical performance of InGaN/GaN nanorod (NR) light emitting diodes (LEDs) fabricated by top-down RIE of c-plane GaN with InGaN quantum wells was investigated. After proper surface treatment a significantly improved device performance could be shown. Therefore, wet chemical removal of damaged material in KOH solution followed by atomic layer deposition of only 10 [Formula: see text] alumina as wide bandgap oxide for passivation were successfully applied. Raman spectroscopy revealed that the initially compressively strained InGaN/GaN LED layer stack turned into a virtually completely relaxed GaN and partially relaxed InGaN combination after RIE etching of NRs. Time-correlated single photon counting provides evidence that both treatments-chemical etching and alumina deposition-reduce the number of pathways for non-radiative recombination. Steady-state photoluminescence revealed that the luminescent performance of the NR LEDs is increased by about 50% after KOH and 80% after additional alumina passivation. Finally, complete NR LED devices with a suspended graphene contact were fabricated, for which the effectiveness of the alumina passivation was successfully demonstrated by electroluminescence measurements.

Exogenous fibroblast growth factor 9 attenuates cartilage degradation and aggravates osteophyte formation in post-traumatic osteoarthritis

OBJECTIVE

The aim of the present study is to investigate the effects of exogenous fibroblast growth factor (FGF)9 on the progression of post-traumatic osteoarthritis (OA).

DESIGN

The expression of FGF9 in articular cartilage with OA is detected by immunohistochemistry (IHC). The effects of intra-articular exogenous FGF9 injection on post-traumatic OA induced by the destabilization of the medial meniscus (DMM) surgery are evaluated. Cartilage changes and osteophyte formation in knee joints are investigated by histological analysis. Changes in subchondral bone are evaluated by microcomputed tomography (micro-CT). The effect of exogenous FGF9 on an interleukin-1β (IL-1β)-induced ex vivo OA model of human articular cartilage tissues is also evaluated.

RESULTS

FGF9 expression was down-regulated in articular chondrocytes of OA but ectopically induced at sites of osteophyte formation. Intra-articular injection of exogenous FGF9 attenuated articular cartilage degradation in mice after DMM surgery. Exogenous FGF9 suppressed collagen X and MMP13 expressions in OA cartilage, while promoted collagen II expression. Similar results were observed in IL-1β-induced ex vivo OA model. Intra-articular injection of FGF9 had no significant effect on the subchondral bone of knee joints after DMM surgery, but aggravated osteophyte formation. The expressions of SOX9 and collagen II, and cell proliferation were up-regulated at sites of initial osteophyte formation in mice with exogenous FGF9 treatment.

CONCLUSIONS

Intra-articular injection of exogenous FGF9 delays articular cartilage degradation in post-traumatic OA, while aggravates osteophyte formation.

Comparison of Utilization and Clinical Outcomes for Belatacept- and Tacrolimus-Based Immunosuppression in Renal Transplant Recipients

The performance of belatacept in a real clinical setting has not been reported. A retrospective cohort study was conducted using registry data comparing 1-year clinical outcomes between belatacept- and tacrolimus-treated adult kidney transplant recipients (KTRs) from January 6, 2011, through January 12, 2014. Of 50 244 total patients, 417 received belatacept plus tacrolimus, 458 received belatacept alone, and 49 369 received tacrolimus alone at discharge. In the overall study cohort, belatacept alone was associated with a higher risk of 1-year acute rejection, with the highest rates associated with non-lymphocyte-depleting induction (adjusted hazard ratio 2.65, 95% confidence interval 1.90-3.70, p < 0.0001). There was no significant difference in rejection rates between belatacept plus tacrolimus and tacrolimus alone. In KTRs who met inclusion criteria for the Belatacept Evaluation of Nephroprotection and Efficacy as First-line Immunosuppression Trial-Extended Criteria Donors (BENEFIT-EXT), 1-year kidney function was higher with belatacept plus tacrolimus and belatacept alone versus tacrolimus alone (mean estimated GFR 65.6, 60.4 and 54.3 mL/min per 1.73 m² , respectively; p < 0.001). The incidence of new-onset diabetes after transplantation was significantly lower with belatacept plus tacrolimus and belatacept alone versus tacrolimus alone (1.7%, 2.2%, and 3.8%, respectively; p = 0.01). Despite improved graft function and metabolic complications with belatacept alone, it may be advisable to add short-term tacrolimus in the first year after transplant and to consider lymphocyte-depleting induction in patients with high rejection risk, as the risk-benefit ratio allows.

[Pedigree survey in a family with hereditary protein S deficiency]

Objective: To observe the clinical feature of familiar hereditary protein S deficiency(HPSD), and to explore the related gene mutations. Methods: A total of seven family members were enrolled in this study and examined during the June to September 2015. Medical histories of the families were analyzed to detect HPSD according to the diagnostic criteria. PROS1 genes of the proband and her family were analyzed. DNA was extracted from peripheral blood. The 15 exons and their intron-exon boundaries of PROS1 were amplified with PCR, and the PCR products were sequenced and analyzed to identify potential mutations. Medical histories from the family members died prior this study were also obtained. Results: Four out of 7 family members of 2 generations were diagnosed as HPSD. The proband suffered from pulmonary embolism, her elder brother suffered from cerebral infarction and her niece suffered from deep vein thrombosis. A missense mutation at the 1063 bp of cDNA(c.1063C>T)was detected in the exon 10 of PROS1, which resulted in arginine 355 to cysteine replacement in the first ball domain of laminin of the protein S(p.R355C). Conclusion: HPSD is an autosomal dominant genetic disease, patients often suffer from recurring vein thrombosis and pulmonary embolism. A missense mutation(c.1063C>T, p. R355C)of PROS1 was discovered in this Chinese family with HPSD, thus, this mutation might be the genetic basis responsible for these family members with HPSD .

Downregulation of miR-145-5p correlates with poor prognosis in gastric cancer

OBJECTIVE

The aim of this study was to explore the clinical significance of miR-145-5p expression in gastric cancer (GC).

PATIENTS AND METHODS

Expression of miR-145-5p was evaluated by qRT- PCR in tumor and normal gastric tissues in 145 GC patients. The correlation between the miR-145-5p expression and clinicopathological parameters was investigated. Finally, the survival was assessed by the Kaplan-Meier method and proportional hazards model.

RESULTS

Expression levels of miR-145-5p in GC tissues were significantly lower than those in adjacent normal tissues (p < 0.001). MiR-145-5p expression was significantly associated with lymph node metastasis, metastasis stage, and distant metastasis (all p < 0.05). Furthermore, Patients with low miR-145-5p expression had poorer overall survival time than those with high miR-145-5p expression (p = 0.014). Moreover, univariate and multivariate Cox analysis showed that miR-145-5p was an independent prognostic indicator for OS (p = 0.011).

CONCLUSIONS

MiR-145-5p is down-expressed in GC, and can be used as a marker of poor prognosis in GC patients.

Structural evolution and mechanical behaviour of Pt nanoparticle superlattices at high pressure

High pressure is an effective means for tuning the interparticle distances of nanoparticle (NP) superlattices and thus for modifying their physical properties and functionalities. In this work, we determined the evolution of inter-NP distances of a Pt NP superlattice with increasing pressure using an in situ synchrotron small-angle X-ray scattering (SAXS) technique in a diamond-anvil cell (DAC). Transmission electron microscopy (TEM) was used to characterize the microstructures of pre- and post-compression samples. Our results demonstrate that the evolution of Pt NP assemblies with increasing pressure consists of four stages: (1) ligand elastic response, (2) uniform compression, (3) ligand detachment from NP surfaces, and (4) deviatoric compression of ligands between neighboring NPs. By controlling the magnitudes of applied pressure and deviatoric stress, one can sinter NPs into novel architectures such as nanowires and nanoceramics.

Photoluminescence characterisations of a dynamic aging process of organic-inorganic CH3NH3PbBr3 perovskite

After unprecedented development of organic-inorganic lead halide perovskite solar cells over the past few years, one of the biggest barriers towards their commercialization is the stability of the perovskite material. It is thus important to understand the interaction between the perovskite material and oxygen and/or humidity and the associated degradation process in order to improve device and encapsulation design for better durability. Here we characterize the dynamic aging process in vapour-assisted deposited (VASP) CH3NH3PbBr3 perovskite thin films using advanced optical techniques, such as time-resolved photoluminescence and fluorescence lifetime imaging microscopy (FLIM). Our investigation reveals that the perovskite grains grow spontaneously and the larger grains are formed at room temperature in the presence of moisture and oxygen. This crystallization process leads to a higher density of defects and a shorter carrier lifetime, specifically in the larger grains. Excitation-intensity-dependent steady-state photoluminescence shows both N2 stored and aged perovskite exhibit a super-linear increase of photoluminescence intensity with increasing excitation intensity; and the larger slope in aged sample suggests a larger density of defects is generated, consistent with time-resolved PL measurements.

The role of cathepsin K in oral and maxillofacial disorders

Cathepsin K (CTSK) was thought to be a collagenase, specifically expressed by osteoclasts, and played an important role in bone resorption. However, more and more research found that CTSK was expressed in more extensive cells, tissues, and organs. It may not only participate in regulating human physiological activity, but also be closely related to a variety of disease. In this review, we highlight the relationship between CTSK and oral and maxillofacial disorders on the following three aspects: oral and maxillofacial abnormities in patients with pycnodysostosis caused by CTSK mutations, oral and maxillofacial abnormities in Ctsk(-/-) mice, and the role of CTSK in oral and maxillofacial diseases, including periodontitis, peri-implantitis, tooth movement, oral and maxillofacial tumor, root resorption, and periapical disease.

A high-throughput RNA-seq approach to profile transcriptional responses

In recent years RNA-seq protocols have been developed to investigate a variety of biological problems by measuring the abundance of different RNAs. Many study designs involve performing expensive preliminary studies to screen or optimize experimental conditions. Testing a large number of conditions in parallel may be more cost effective. For example, analyzing tissue/environment-specific gene expression generally implies screening a large number of cellular conditions and samples, without prior knowledge of which conditions are most informative (e.g., some cell types may not respond to certain treatments). To circumvent these challenges, we have established a new two-step high-throughput RNA-seq approach: the first step consists of gene expression screening of a large number of conditions, while the second step focuses on deep sequencing of the most relevant conditions (e.g., largest number of differentially expressed genes). This study design allows for a fast and economical screen in step one, with a more efficient allocation of resources for the deep sequencing of the most biologically relevant libraries in step two. We have applied this approach to study the response to 23 treatments in three lymphoblastoid cell lines demonstrating that it should also be useful for other high-throughput transcriptome profiling applications requiring iterative refinement or screening.

Neuroprotective effect of astaxanthin against glutamate-induced cytotoxicity in HT22 cells: Involvement of the Akt/GSK-3β pathway

Oxidative stress (OS) mediated the pathogenesis of Alzheimer's disease (AD). Astaxanthin (ATX) has been reported to exert antioxidant activities as well as neuroprotective effects in vivo and in vitro. But it is still unknown whether the Akt/glycogen synthase kinase-3β (GSK-3β) signaling mediated the neuroprotective effect of ATX in HT22 cells. Flow cytometric analysis was used to evaluate reactive oxygen species (ROS) generation. Caspase and PARP activity was measured. The expressions of heme oxygenase-1 (HO-1), nuclear factor-E2-related factor 2 (Nrf2), Bcl-2, Bax, apoptosis-inducing factor (AIF), cytochrome-c (Cyto-c), p-Akt and p-GSK-3β were evaluated to elucidate the underlying mechanism. Our results showed that ATX significantly attenuated glutamate-induced cell viability loss and lactate dehydrogenase (LDH) release, decreased the expression of caspase-3/8/9 activity and cleaved PARP, and suppressed the intracellular accumulation of ROS in HT22 cells after exposure to glutamate. ATX also increased the mitochondrial expression of AIF, Cyto-c as well as Bax while decreased Bcl-2. Moreover, ATX also induced the HO-1 expression in a dose and time-dependent manner, increased the antioxidant-responsive element (ARE) activity and nuclear Nrf2 expression. Furthermore, treatment with ATX restored the p-Akt and p-GSK-3β (Ser9) as well as HO-1 expression reduced by glutamate. This protective effect was partially blocked by the inhibitors lithium chloride treatment in HT22, indicating the involvement of Akt/GSK-3β inactivation during the neuroprotective effect of ATX. Our results provide the first evidence that ATX can protect glutamate-induced cytotoxicity in HT22 via attenuating caspase activation and mitochondrial dysfunction and modulating the Akt/GSK-3β signaling, indicating ATX may be useful for the treatment of neurodegenerative disorders such as AD.

Parallel enzyme-linked immunosorbent assay screening for human immunodeficiency virus among blood donors in five Chinese blood centres: a retrospective analysis

AIMS

To evaluate the strategy of parallel screening with different enzyme-linked immunosorbent assays (ELISA) among Chinese blood donors.

BACKGROUND

Parallel screening with ELISA has been the main strategy to detect human immunodeficiency virus (HIV) in blood donations in China for more than a decade. The performance of the strategy should be analysed.

METHODS

A total of 821,927 donations collected from five Chinese blood centres in 2008-2010 were tested using two third-generation ELISAs by different manufacturers licenced and confirmed by the Western blot (WB) in this study. The confirmatory positive predictive values (PPV), false positive rates (FPR), false negative rates (FNR) and potential risks for transfusion resulting from single or sequential ELISA screening were evaluated.

RESULTS

A total of 5318 (0·647%) of donations screened HIV reactive and were discarded. WB confirmatory results on 1668 available samples suggested that PPVs for dual ELISA, one round ELISA reactive and grey zone samples were 75·1, 0·7 and 0·5%, respectively. Eight out of 1124 one round ELISA reactive and 1 out of 195 grey zone samples were WB confirmed positive. All but one ELISA assay displayed comparable PPVs but variable FPRs and FNRs that differed by blood centre.

CONCLUSIONS

In the absence of nucleic acid testing (NAT), parallel ELISA screening prevented a substantial number of HIV infected donations from entering the Chinese blood supply. However, the loss of false positive donors should be re-evaluated especially given the frequently reported blood supply shortage in China.

Comparisons of sarcopenia prevalence based on different diagnostic criteria in Chinese older adults

The study aimed to describe the prevalence of sarcopenia and discussed the applicability of different diagnostic criteria in Chinese older adults. 286 Chinese adults (136 men and 150 women) aged 60-88 were recruited. The prevalence of sarcopenia were calculated using different diagnostic criteria. Physical functioning was compared in sarcopenic and non-sarcopenic older adults. Compared with the standard of EWGSOP (European Working Group on Sarcopenia in Older People), the prevalence of sarcopenia was higher when the IWGS (International Working Group on Sarcopenia) standard was applied (Men: 7.4% vs. 0.8%; Women: 4.7% vs. 0%). If the AWGS (Aisa Working Group on Sarcopenia) standard was applied, the prevalence was 5.9% in men and 0.7% in women. In conclusion, the prevalence of sarcopenia in Chinese older adults ranged from 0% to around 10% when the diagnostic criteria of IGWS, EWGSOP and AGWS were applied. Further studies are still needed to investigate appropriate diagnostic criterion of sarcopenia for Chinese population.

Oncogenic and tumor suppressive roles of microRNAs in apoptosis and autophagy

MicroRNAs (miRNAs), small and non-coding endogenous RNAs ∼22 nucleotides (nt) in length, have been known to regulate approximately 30 % of human gene expression at the post-transcriptional and translational levels. Accumulating data have demonstrated that certain miRNAs could exert an oncogenic and/or tumor suppressive function and might play essential roles in the regulation of apoptosis and autophagy in cancer. In this review, we summarize that certain oncogenic and tumor suppressive miRNAs could modulate apoptotic pathways in different types of cancer. Subsequently, we demonstrate that other miRNAs might play regulatory roles in the autophagic pathways of cancer. A limited number of oncogenic/tumor suppressive miRNAs could regulate apoptosis and autophagy, respectively, and cooperatively. Taken together, these findings would provide a new clue to elucidate more apoptotic and/or autophagic mechanisms of miRNAs for designing potential novel therapeutic strategies in cancer.

HIV Tat protein affects circadian rhythmicity by interfering with the circadian system

OBJECTIVES

Sleep disorders are common in patients with HIV/AIDS, and can lead to poor quality of life. Although many studies have investigated the aetiology of these disorders, it is still unclear whether impaired sleep quality is associated with HIV itself, social problems, or side effects of antiretroviral therapy (ART). Moreover, despite its known neurological associations, little is known about the role of the trans-activator of transcription (Tat) protein in sleep disorders in patients with HIV/AIDS. The purpose of this study was to test the hypothesis that the sleep quality of patients with HIV/AIDS affected by an altered circadian rhythm correlates with cerebrospinal HIV Tat protein concentration.

METHODS

Ninety-six patients with HIV/AIDS between 20 and 69 years old completed the Pittsburgh Sleep Quality Index. Their circadian rhythm parameters of blood pressure, Tat concentration in cerebrospinal fluid, melatonin concentration, CD4 cell count and HIV RNA viral load in serum were measured.

RESULTS

The circadian amplitude of systolic blood pressure and the score for sleep quality (Pittsburgh Sleep Quality Index) were negatively correlated with HIV Tat protein concentration, while the melatonin value was positively correlated with Tat protein concentration.

CONCLUSIONS

The HIV Tat protein affects circadian rhythmicity by interfering with the circadian system in patients with HIV/AIDS and further increases the melatonin excretion value. A Tat protein-related high melatonin value may counteract HIV-related poor sleep quality during the progression of HIV infection. This study provides the first clinical evidence offering an explanation for why sleep quality did not show an association with progression of HIV infection in previous studies.

Association of serum homocysteine levels with the severity and calcification of coronary atherosclerotic plaques detected by coronary CT angiography

AIM

In this study, we aim to evaluate the association of risk factors including homocysteine (Hcy) with the severity and burden of coronary atherosclerotic plaques detected by computed tomography angiography (CTA).

METHODS

Six hundred fifty-nine subjects who underwent CTA for the assessment of coronary artery disease (CAD) were studied. All the subjects enrolled had no clinical cardiovascular disease symptoms. Logistic regression showed apart from age, hypertension, smoking, triglyceride, low-density lipoprotein (LDL) cholesterol, and total bilirubin, Hcy was an independently risk factor of the severity of coronary disease. And Hcy was also found an independent predictor for the presence of calcified plaque. When the participants were divided into 4 groups according to serum Hcy quartiles (Q1-Q4 groups), both the percentage of patients with >50% stenosis and the percentage of patients with calcified plaque were higher in Q4 compared to other groups. The OR of Hcy (>15 µmol/L) for >50% stenosis was 2.212 (95% CI=1.119 to 4.375, P=0.022) and the OR for Hcy (>15 µmol/L) for calcification was 1.668 (95% CI=1.030 to 2.699, P=0.037) respectively.

CONCLUSION

Our study shows Hcy is independently associated with both the severity and calcified plaque detected by CTA. Hcy may provide additional information about CAD in the subjects without clinical symptoms.

In silico analysis and experimental validation of azelastine hydrochloride (N4) targeting sodium taurocholate co-transporting polypeptide (NTCP) in HBV therapy

OBJECTIVES

The aim of this study was to explore sodium taurocholate co-transporting polypeptide (NTCP) exerting its function with hepatitis B virus (HBV) and its targeted candidate compounds, in HBV therapy.

MATERIALS AND METHODS

Identification of NTCP as a novel HBV target for screening candidate small molecules, was used by phylogenetic analysis, network construction, molecular modelling, molecular docking and molecular dynamics (MD) simulation. In vitro virological examination, q-PCR, western blotting and cytotoxicity studies were used for validating efficacy of the candidate compound.

RESULTS

We used the phylogenetic analysis of NTCP and constructed its protein-protein network. Also, we screened compounds from Drugbank and ZINC, among which five were validated for their authentication in HepG 2.2.15 cells. Then, we selected compound N4 (azelastine hydrochloride) as the most potent of them. This showed good inhibitory activity against HBsAg (IC50 = 7.5 μm) and HBeAg (IC50 = 3.7 μm), as well as high SI value (SI = 4.68). Further MD simulation results supported good interaction between compound N4 and NTCP.

CONCLUSIONS

In silico analysis and experimental validation together demonstrated that compound N4 can target NTCP in HepG2.2.15 cells, which may shed light on exploring it as a potential anti-HBV drug.

Novel gammaherpesvirus functions encoded by bovine herpesvirus 6 (bovine lymphotropic virus)

The genus Macavirus of the subfamily Gammaherpesvirinae includes viruses that infect lymphoid cells of domestic and wild ruminants and swine, causing asymptomatic latent infections in reservoir hosts. Here, we describe the genome of bovine herpesvirus 6 (BoHV-6), a macavirus ubiquitous in healthy cattle populations. The BoHV-6 genome exhibited architecture conserved in macaviruses, including a repetitive H-DNA region and unique 141 kbp L-DNA region predicted to encode 77 genes. BoHV-6 encoded, in variable genomic regions, a novel complement of genes relative to other characterized macaviruses, probably contributing to distinctive aspects of BoHV-6 infection biology and host range. Most notably, BoHV-6 encoded the first herpesviral protein (Bov2.b2) similar to cellular ornithine decarboxylase, an enzyme that catalyses the first and rate-limiting step in the biosynthesis of polyamines. Bov2.b2 conceivably mediates a novel mechanism by which BoHV-6 promotes cell-cycle-dependent viral replication.

Cab45S inhibits the ER stress-induced IRE1-JNK pathway and apoptosis via GRP78/BiP

Disturbance of endoplasmic reticulum (ER) homeostasis causes ER stress and leads to activation of the unfolded protein response, which reduces the stress and promotes cell survival at the early stage of stress, or triggers cell death and apoptosis when homeostasis is not restored under prolonged ER stress. Here, we report that Cab45S, a member of the CREC family, inhibits ER stress-induced apoptosis. Depletion of Cab45S increases inositol-requiring kinase 1 (IRE1) activity, thus producing more spliced forms of X-box-binding protein 1 mRNA at the early stage of stress and leads to phosphorylation of c-Jun N-terminal kinase, which finally induces apoptosis. Furthermore, we find that Cab45S specifically interacts with 78-kDa glucose-regulated protein/immunoglobulin heavy chain binding protein (GRP78/BiP) on its nucleotide-binding domain. Cab45S enhances GRP78/BiP protein level and stabilizes the interaction of GRP78/BiP with IRE1 to inhibit ER stress-induced IRE1 activation and apoptosis. Together, Cab45S, a novel regulator of GRP78/BiP, suppresses ER stress-induced IRE1 activation and apoptosis by binding to and elevating GRP78/BiP, and has a role in the inhibition of ER stress-induced apoptosis.

Taurine improves functional and histological outcomes and reduces inflammation in traumatic brain injury

We investigated the effect of taurine on inflammatory cytokine expression, on astrocyte activity and cerebral edema and functional outcomes, following traumatic brain injury (TBI) in rats. 72 rats were randomly divided into sham, TBI and Taurine groups. Rats subjected to moderate lateral fluid percussion injury were injected intravenously with taurine (200mg/kg) or saline immediately after injury or daily for 7days. Functional outcome was evaluated using Modified Neurological Severity Score (mNSS). Glial fibrillary acidic protein (GFAP) of the brain was measured using immunofluorescence. Concentration of 23 cytokines and chemokines in the injured cortex at 1 and 7days after TBI was assessed by Luminex xMAP technology. The results showed that taurine significantly improved functional recovery except 1day, reduced accumulation of GFAP and water content in the penumbral region at 7days after TBI. Compared with the TBI group, taurine significantly suppressed growth-related oncogene (GRO/KC) and interleukin (IL)-1β levels while elevating the levels of regulated on activation, normal T cell expressed and secreted (RANTES) at 1day. And taurine markedly decreased the level of 17 cytokine: eotaxin, Granulocyte colony-stimulating factor (G-CSF), Granulocyte-macrophage colony-stimulating factor (GM-CSF), interferon-gamma (IFN-γ), IL-1α, IL-1β, IL-4, IL-5, IL-6, IL-10, IL-12p70, IL-13, IL-17, leptin, monocyte chemotactic protein-1 (MCP-1), tumor necrosis factor-alpha (TNF-α), vascular endothelial growth factor (VEGF), and only increased the level of MIP-1α in a week. The results suggest that taurine effectively mitigates the severity of brain damage in TBI by attenuating the increase of astrocyte activity and edema as well as pro-inflammatory cytokines.

Population Structures of 'Candidatus Liberibacter asiaticus' in Southern China

Huanglongbing (HLB) is a highly detrimental citrus disease associated with 'Candidatus Liberibacter asiaticus', a nonculturable alpha-proteobacterium. Characterization of the bacterial populations is important for development of disease management strategies. In this study, the 'Ca. L. asiaticus' populations in eight provinces in southern China where HLB is endemic were analyzed based on tandem repeat number (TRN) variations in a previously characterized genomic locus CLIBASIA_01645. Of the 224 HLB samples collected, 175 (78.3%) samples yielded single polymerase chain reaction (PCR) amplicons (the single amplicon group, SAG) and 49 (21.7%) samples produced multiple PCR amplicons (the multiple amplicon group, MAG). Variations in SAG are summarized by Nei's diversity index (H) and ratio of TRN ≤ 10/TRN > 10 genotypes (R10). Variations in the MAG are described by the percentage of occurrence (PMAG). At an orchard-level comparison, the 'Ca. L. asiaticus' population from a Guangdong orchard (n = 24) showed H = 0.50, R10 = 23, and PMAG = 0, significantly different from that of the non-Guangdong orchards in Yunnan (n = 23), H = 0.83, R10 = 2.3, and PMAG = 11.5, and in Hainan (n = 35), H = 0.88, R10 = 1.5, and PMAG = 16.7. In a region-level consideration, the Guangdong 'Ca. L. asiaticus' population (n = 78) was H = 0.77, R10 = 25, and PMAG = 1.3, whereas the non-Guangdong population (n = 84) was H = 0.91, R10 = 1.6, and PMAG = 26.9. Overall, significant differences were observed between the 'Ca. L. asiaticus' population from Guangdong Province and those from the other provinces. A strong aggregation of TRN = 6, 7, and 8 genotypes is characteristic to the 'Ca. L. asiaticus' population in Guangdong. Referenced to genome annotation, we propose that rearrangement of tandem repeats at locus CLIBASIA_01645 could be associated with bacterial environmental adaptation.