Stagonosporopsis pogostemonis: A Novel Ascomycete Fungus Causing Leaf Spot and Stem Blight on Pogostemon cablin (Lamiaceae) in South China

Pogostemon cablin is one of the well-known Southern Chinese medicinal plants with detoxification, anti-bacterial, anti-inflammatory, and other pharmacological functions. Identification and characterization of phytopathogens on P. cablin are of great significance for the prevention and control of diseases. From spring to summer of 2019 and 2020, a leaf spot disease on Pogostemon cablin was observed in Guangdong Province, South China. The pathogen was isolated and identified based on both morphological and DNA molecular approaches. The molecular identification was conducted using multi-gene sequence analysis of large subunit (LSU), the nuclear ribosomal internal transcribed spacer (ITS), beta-tubulin (β-tubulin), and RNA polymerase II (rpb2) genes. The causal organism was identified as Stagonosporopsis pogostemonis, a novel fungal species. Pathogenicity of Stagonosporopsis pogostemonis on P. cablin was fulfilled via confining the Koch's postulates, causing leaf spots and stem blight disease. This is the first report of leaf spot diseases on P. cablin caused by Stagonosporopsis species worldwide.

Single-cell RNA sequencing identifies molecular targets associated with poor in vitro maturation performance of oocytes collected from ovarian stimulation

STUDY QUESTION

What is the transcriptome signature associated with poor performance of rescue IVM (rIVM) oocytes and how can we rejuvenate them?

SUMMARY ANSWER

The GATA-1/CREB1/WNT signalling axis was repressed in rIVM oocytes, particularly those of poor quality; restoration of this axis may produce more usable rIVM oocytes.

WHAT IS KNOWN ALREADY

rIVM aims to produce mature oocytes (MII) for IVF through IVM of immature oocytes collected from stimulated ovaries. It is not popular due to limited success rate in infertility treatment. Genetic aberrations, cellular stress and the absence of cumulus cell support in oocytes could account for the failure of rIVM.

STUDY DESIGN, SIZE, DURATION

We applied single-cell RNA sequencing (scRNA-seq) to capture the transcriptomes of human in vivo oocytes (IVO) (n = 10) from 7 donors and rIVM oocytes (n = 10) from 10 donors. The effects of maternal age and ovarian responses on rIVM oocyte transcriptomes were also studied. In parallel, we studied the effect of gallic acid on the maturation rate of mouse oocytes cultured in IVM medium with (n = 84) and without (n = 85) gallic acid.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Human oocytes were collected from donors aged 28-41 years with a body mass index of <30. RNA extraction, cDNA generation, library construction and sequencing were performed in one preparation. scRNA-seq data were then processed and analysed. Selected genes in the rIVM versus IVO comparison were validated by quantitative real-time PCR. For the gallic acid study, we collected immature oocytes from 5-month-old mice and studied the effect of 10-μM gallic acid on their maturation rate.

MAIN RESULTS AND THE ROLE OF CHANCE

The transcriptome profiles of rIVM/IVO oocytes showed distinctive differences. A total of 1559 differentially expressed genes (DEGs, genes with at least 2-fold change and adjusted P < 0.05) were found to be enriched in metabolic processes, biosynthesis and oxidative phosphorylation. Among these DEGs, we identified a repression of WNT/β-catenin signalling in rIVM when compared with IVO oocytes. We found that oestradiol levels exhibited a significant age-independent correlation with the IVO mature oocyte ratio (MII ratio) for each donor. rIVM oocytes from women with a high MII ratio were found to have over-represented cellular processes such as anti-apoptosis. To further identify targets that contribute to the poor clinical outcomes of rIVM, we compared oocytes collected from young donors with a high MII ratio with oocytes from donors of advanced maternal age and lower MII ratio, and revealed that CREB1 is an important regulator. Thus, our study identified that GATA-1/CREB1/WNT signalling was repressed in both rIVM oocytes versus IVO oocytes and in rIVM oocytes of lower versus higher quality. Consequently we investigated gallic acid, as a potential antioxidant substrate in human rIVM medium, and found that it increased the mouse oocyte maturation rate by 31.1%.

LARGE SCALE DATA

Raw data from this study can be accessed through GSE158539.

LIMITATIONS, REASONS FOR CAUTION

In the rIVM oocytes of the high- and low-quality comparison, the number of samples was limited after data filtering with stringent selection criteria. For the oocyte stage identification, we were unable to predict the presence of oocyte spindle, so polar body extrusion was the only indicator.

WIDER IMPLICATIONS OF THE FINDINGS

This study showed that GATA-1/CREB1/WNT signalling was repressed in rIVM oocytes compared with IVO oocytes and was further downregulated in low-quality rIVM oocytes, providing us the foundation of subsequent follow-up research on human oocytes and raising safety concerns about the clinical use of rescued oocytes.

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by the Collaborative Research Fund, Research Grants Council, C4054-16G, and Research Committee Funding (Research Sustainability of Major RGC Funding Schemes), The Chinese University of Hong Kong. The authors have no conflicts of interest to declare.

[Fluorescence assay for the detection of apurinic/apyrimidinic endonuclease 1 (APE1) activity in human blood samples]

OBJECTIVE

To develop a simple, sensitive and robust method for rapid detection of human apurinic/apyrimidinic endonuclease 1 (APE1) in various biological samples.

METHODS

An abasic site-containing DNA probe with a sequence of 5'-T*T*C*C*T*C*T(ROX)AGAGXCGTT (BHQ2)C*A*C*T*G*T*AGTTTATA*C*A*G*T*GAATCTCTCTAG*T*C*T-3' ["X" represents AP site; The phosphorothioated nucleotides (at 3' side) are indicated with an asterisk after the nucleotides; ROX is 6-carboxy-X-rhodamine and BHQ2 is Black Hole quencher 2] was synthesized and used for the detection. In the presence of APE1, the DNA probe could be specifically hydrolyzed by the enzyme and release the fluorophore, resulting in strong fluorescence emission. The activity of APE1 was determined according to the rate of increase in fluorescence intensity. In this work, we modified the reaction buffer and significantly improved the performance of the method. Moreover, the method was further extended to measure the contents of APE1 in the protein extraction from peripheral blood mononuclear cells (PBMCs) extracted from human whole blood samples by density gradient centrifugation. The assay was also applied to measure the activity of APE1 in human serum samples.

RESULTS

With a new reaction buffer composed of 0.04% (V/V) Triton X-100, 50 mmol/L KAc, 20 mmol/L Tris-Ac, 10 mmol/L Mg(Ac)2 and 1 mmol/L dithiothreitol (DTT), the method achieved a detection limit of 0.005 U/mL (3 pg/mL) and a linear response ranging from 6 pg/mL to 1.2 ng/mL. The contents of APE1 in the protein extraction from PBMCs of eight blood samples were measured to be in the range from 0.061 to 0.40 ng/μg protein, with an average of 0.16 ng/μg protein. The recovery was 98%±5% (n=3). The levels of APE1 in the sera from 102 normal individuals (51 male and 51 female, age range: 59-75 years) were observed to be from 0.13 to 0.34 ng/mL, with a recovery of 96%±15% (n=3).

CONCLUSION

The new fluorescence assay was simple, rapid and sensitive, providing a practical tool to measure the activity of APE1 in serum samples and cell extracts. It also holds great potential in measurement of APE1 in many other biological samples for clinical test and laboratory research.

Gas Chromaotography-Mass Spectrometry Analysis of Insecticidal Essential Oil Derived from Chinese Ainsliaea fragrans Champ ex Benth (Compositae)

Purpose: To investigate the chemical composition and insecticidal activity of the essential oil of the aerial parts of Ainsliaea fragrans against maize weevils (Sitophilus zeamais).Methods: The essential oil of A. fragrans aerial parts was obtained by hydrodistillation and analyzed by gas chromatography (GC) and gas chromaotography-mass spectrometry (GC-MS). Contact toxicity of the essential oil and its major constituents was determined by topical application against S. zeamais.Results: A total of 30 components of the essential oil were identified. The major constituents were myristicin (41.3 %), elemicine (11.9 %), cis-isosafrole (11.5 %), borneol (9.1 %) and caryophyllene (8.8 %). The essential oil of A. fragrans exhibited contact toxicity against S. zeamais with LC50 value of 50.7 μg/adult. Elemicine possessed the strongest contact toxicity (LC50 = 13.5 μg/adult) while cis-isosafrole, myristicin, caryophyllene and borneol had LC50 values of 31.2 μg/adult, 43.4 μg/adult, 57.9 μg/adult, and 98.4 μg/adult, respectively.Conclusion: The study indicates that the essential oil of A. fragrans aerial parts and its major constituents have a potential for development into natural insecticides for the control of grain storage insects.Keywords: Ainsliaea fragrans, Sitophilus zeamais, Contact toxicity, Elemicine, Essential oil, Grain storage