Development of a SCAR marker linked to fungal pathogenicity of rice blast fungus Magnaporthe Oryzae.

PCR-based molecular approaches including RAPD (random amplified polymorphic DNA), ISSR (inter-simple sequence repeat), and SRAP (sequence-related amplified polymorphism) are commonly used to analyze genetic diversity. The aims of this study are to analyze genetic diversity of M. oryzae isolates using PCR-based molecular approaches such as RAPD, ISSR, and SRAP and to develop SCAR marker linked to the pathogenicity of rice blast fungus. Twenty Magnaporthe oryzae isolates were collected mainly from the south of Vietnam and assessed for genetic variation by RAPD, ISSR, and SRAP methods. The comparison of those methods was conducted based on the number of polymorphic bands, percentage of polymorphism, PIC values, and phylogenetic analysis. Then, sequenced characterized amplified region (SCAR) markers were developed based on specific bands linked to fungal pathogenicity of rice blast fungus, M. oryzae. The results indicated that SRAP markers yielded the greatest number of polymorphic bands (174) and occupied 51.7% with polymorphism information content (PIC) value of 0.66. Additionally, the SRAP approach showed stability and high productivity compared with RAPD and ISSR. The SCAR marker developed from the SRAP method identified the presence of the avirulence AVR-pita1 gene involving fungal pathogenicity that can break down blast resistance in rice cultivars. The consistency of SCAR marker obtained in this study showed its efficiency in rapid in-field detection of fungal pathogenicity. SCAR marker developed from SRAP technique provides a useful tool for improving the efficiency of blast disease management in rice fields.

Loop-mediated isothermal amplification (LAMP) assay for detection of sesame phyllody phytoplasmas in Vietnam.

Phloem-limiting phytoplasmas are known to be causal agents of phyllody, which is recognized by the abnormal development of floral structures resulting in serious yield losses in sesame plants. Currently, identification of the various groups of phytoplasmas that cause sesame phyllody (SP) is conducted by nested PCR, RFLP, and multiplex real-time qPCR assays. However, these methods require intensive labor and are costly and time-consuming so can only be undertaken in well-equipped labs. Here, diagnostic loop-mediated isothermal amplification (LAMP)-based assays allowing rapid detection of specific groups of phytoplasmas within 30 min were developed based on detection of the 16S rRNA sequence of phytoplasmas. Universal 16S rRNA phytoplasma primers and seven primer sets of different 16Sr group phytoplasmas (16SrI, 16SrII, 16SrIII, 16SrIV, 16SrV, 16SrX, 16SrXI) and universal plant cytochrome oxidase (cox) gene primers were used to detect 16S rRNA group phytoplasma sequences and the cox gene in sesame plants. The LAMP assays were carried out using a real-time fluorometer with amplification plots and annealing curves visualized directly. Results demonstrated that the 16SrI and 16SrII group phytoplasmas were causal agents of sesame phyllody in Vietnam. LAMP-based assays for in-field detection of sesame phyllody-causing phytoplasmas revealed advantages and potential applicability in comparison with conventional approaches. To the best of our knowledge, this is the first assessment of multiple phytoplasma infection associated with sesame phyllody disease in Vietnam using LAMP-based assays.

Closed tube loop-mediated isothermal amplification assay for rapid detection of hepatitis B virus in human blood.

Recently, many studies have demonstrated the significant advantages of loop-mediated isothermal amplification (LAMP) based methods over serological tests and PCR for rapid detection of microbial pathogens. Here, a rapid LAMP assay was developed to detect the hepatitis B virus (HBV) from DNA, and particularly, blood samples from infected patients using a commercially available master mix and portable real-time fluorometer. The final optimized fluorescence-based LAMP assay provided significant amplification time of less than 15 minutes compared with over 1 hour for PCR and an opened tube LAMP system described previously. Results indicated that fluorescence-based LAMP assay was more sensitive than PCR as a rapid, sensitive, efficient, and highly reliable approach for rapid detection of HBV.

Expression of Plasma hsa-miR122 in HBV-Related Hepatocellular Carcinoma (HCC) in Vietnamese Patients.

BACKGROUND: Hepatocellular carcinoma (HCC) is the leading cause of cancer-related death in the world and considered as one of the most susceptible cancers in humans. The microRNA molecule, hsa-miR122, considered as a potential biological marker linked with the injury of hepatocellular tissue, is the most common microRNA in human liver cancer. Understanding the expression profile of hsa-miR122 plays an important role in the diagnosis of HCC. OBJECTIVE: Identification and comparison of cut-off values of plasma hsa-miR122 expression were conducted in blood samples of healthy control, HBV infected and HBV-related HCC Vietnamese patients. METHODS AND RESULT: Fifty-two blood samples of healthy control and HBV-related HCC cases, collected between 2015 and 2017 were obtained from Ho Chi Minh City Oncology Hospital, Vietnam. Written informed consent was attained from all patients and the Human Research Ethics Committee, Oncology Hospital (#08/BVUB-HDDD) approved the research protocol. Total RNA was isolated from blood samples with TrizolTM Reagent (Thermo Fisher Scientific, USA). To analyze the expression level of hsa-miR122, miRNA specific reverse transcription was performed using Sensi- FASTTM cDNA Synthesis Kit (Bioline, UK) as described by the manufacturer, followed by running RT-qPCR with SensiFASTTMSYBR No-ROX Kit (Bioline, UK). The housekeeping gene, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was used for normalization. The presence of hsamiR122 and HBV-DNA was identified in human blood using RT-PCR and LAMP techniques. Downregulation of plasma hsa-miR122 was observed in HBV-related HCC patients with a .Ct value of 7.9 ± 2.1 which was significantly lower than found in healthy control (p<0.01). The loss of hsa-miR122 expression was observed in HBV infected patients. We also identified the difference of diagnostic values of this microRNA in different populations and provided a high diagnostic accuracy of HCC (AUC = 0.984 with sensitivity and specificity of 96% and 94%, respectively). CONCLUSION: hsa-miR122 was downregulated in HBV-related HCC patients and found to be lower by approximately 10 fold than in healthy control, resulting in a potential biomarker for microRNA based diagnosis of HCC in human blood.