Selection and Evaluation of Appropriate Reference Genes for RT-qPCR Normalization of Volvariella volvacea Gene Expression under Different Conditions

Selection and validation of reference genes for RT-qPCR in ophiocordyceps sinensis under different experimental conditions

The Chinese caterpillar mushroom, Ophiocordyceps sinensis (O. sinensis), is a rarely medicinal fungus in traditional chinese herbal medicine due to its unique medicinal values, and the expression stability of reference genes is essential to normalize its gene expression analysis. In this study, BestKeeper, NormFinder and geNorm, three authoritative statistical arithmetics, were applied to evaluate the expression stability of sixteen candidate reference genes (CRGs) in O. sinensis under different stress [low temperature (4°C), light treatment (300 lx), NaCl (3.8%)] and different development stages (mycelia, primordia and fruit bodies) and formation of morphologic mycelium (aeriasubstrate, hyphae knot mycelium). The paired variation values indicated that two genes could be enough to accurate standardization exposed to different conditions of O.sinensis. Among these sixteen CRGs, 18S ribosomal RNA (18S rRNA) and beta-Tubulin (β-TUB) showed the topmost expression stability in O.sinensis exposed to all conditions, while glutathione hydrolase proenzym (GGT) and Phosphoglucose isomerase (PGI) showed the least expression stability. The optimal reference gene in different conditions was various. β-TUB and Ubiquitin (UBQ) were identified as the two most stable genes in different primordia developmental stage, while phosphoglucomutase (PGM) with elongation factor 1-alpha (EF1-α) and 18S rRNA with UBQ were the most stably expressed for differentially morphologic mycelium stages and different stresses, respectively. These results will contribute to more accurate evaluation of the gene relative expression levels in O.sinensis under different conditions using the optimal reference gene in real-time quantitative PCR (RT-qPCR) analysis.

Selection and validation of reference genes for normalization of gene expression in Floccularia luteovirens

Floccularia luteovirens is one of the rare edible fungi with high nutritional value found on the Qinghai-Tibet Plateau. However, research at the molecular level on this species is currently constrained due to the lack of reliable reference genes for this species. Thirteen potential reference genes (ACT, GAPDH, EF-Tu, SAMDC, UBI, CLN1, β-TUB, γ-TUB, GTP, H3, UBC, UBC-E2, and GTPBP1) were chosen for the present study, and their expression under various abiotic conditions was investigated. Stability of gene expression was tested using GeNorm, NormFinder, BestKeeper, Delta-Ct, and RefFinder. The results showed that the most suitable reference genes for salt treatment were ACT and EF-Tu. Under drought stress, γ-TUB and UBC-E2 would be suitable for normalization. Under oxidative stress, the reference genes H3 and GAPDH worked well. Under heat stress, the reference genes EF-Tu and γ-TUB were suggested. Under extreme pH stress, UBC-E2 and H3 were appropriate reference genes. Under cadmium stress, the reference genes ACT and UBC-E2 functioned well. In different tissues, H3 and GTPBP1 were appropriate reference genes. The optimal internal reference genes when analyzing all samples were H3 and SAMDC. The expression level of HSP90 was studied to further validate the applicability of the genes identified in this study.

Bioactive Compounds from Endophytic Bacteria Bacillus subtilis Strain EP1 with Their Antibacterial Activities

Endophytic bacteria boost host plant defense and growth by producing vital compounds. In the current study, a bacterial strain was isolated from the Boswellia sacra plant and identified as Bacillus subtilis strain EP1 (accession number: MT256301) through 16S RNA gene sequencing. From the identified bacteria, four compounds-1 (4-(4-cinnamoyloxy)phenyl)butanoic acid), 2 (cyclo-(L-Pro-D-Tyr)), 3 (cyclo-(L-Val-L-Phe)), and 4 (cyclo-(L-Pro-L-Val))-were isolated and characterized by 1D and 2D NMR and mass spectroscopy. Moreover, antibacterial activity and beta-lactam-producing gene inhibition (δ-(l-α-aminoadipyl)-l-cysteinyl-d-valine synthetase (ACVS) and aminoadipate aminotransferase (AADAT)) assays were performed. Significant antibacterial activity was observed against the human pathogenic bacterial strains (E. coli) by compound 4 with a 13 ± 0.7 mm zone of inhibition (ZOI), followed by compound 1 having an 11 ± 0.7 mm ZOI. In contrast, the least antibacterial activity among the tested samples was offered by compound 2 with a 10 ± 0.9 mm ZOI compared to the standard (26 ± 1.2 mm). Similarly, the molecular analysis of beta-lactam inhibition determined that compounds 3 and 4 inhibited the two genes (2- to 4-fold) in the beta-lactam biosynthesis (ACVS and AADAT) pathway. From these results, it can be concluded that future research on these compounds could lead to the inhibition of antibiotic-resistant pathogenic bacterial strains.

Identification and Validation of Common Reference Genes for Normalization of Esophageal Squamous Cell Carcinoma Gene Expression Profiles

Esophageal squamous cell carcinoma (ESCC) is one of the subtypes of esophageal cancer with Chinese characteristics, and its five-year survival rate is less than 20%. Early diagnosis is beneficial to improving the survival rate of ESCC significantly. Quantitative Real-Time Polymerase Chain Reaction is a high-throughput technique that can quantify tumor-related genes for early diagnosis. Its accuracy largely depends on the stability of the reference gene. There is no systematic scientific basis to demonstrate which reference gene expression is stable in ESCC and no consensus on the selection of internal reference. Therefore, this research used four software programs (The comparative delta-Ct method, GeNorm, NormFinder, and BestKeeper) to evaluate the expression stability of eight candidate reference genes commonly used in other tumor tissues and generated a comprehensive analysis by RefFinder. Randomly selected transcriptome sequencing analysis confirmed the SPP1 gene is closely related to ESCC. It was found that the expression trend of SPP1 obtained by RPS18 and PPIA as internal reference genes were the same as that of sequencing. The results show that RPS18 and PPIA are stable reference genes, and PPIA + RPS18 are a suitable reference gene combination. This is a reference gene report that combines transcriptome sequencing analysis and only focuses on ESCC, which makes the quantification more precise, systematic, and standardized, and promotes gene regulation research and the early diagnosis of ESCC in the future.

Systematic Identification and Validation of Suitable Reference Genes for the Normalization of Gene Expression in Prunella vulgaris under Different Organs and Spike Development Stages

The quantitative real-time PCR (qRT-PCR) is an efficient and sensitive method for determining gene expression levels, but the accuracy of the results substantially depends on the stability of the reference gene (RG). Therefore, choosing an appropriate reference gene is a critical step in normalizing qRT-PCR data. Prunella vulgaris L. is a traditional Chinese medicine herb widely used in China. Its main medicinal part is the fruiting spike which is termed Spica Prunellae. However, thus far, few studies have been conducted on the mechanism of Spica Prunellae development. Meanwhile, no reliable RGs have been reported in P. vulgaris. The expression levels of 14 candidate RGs were analyzed in this study in various organs and at different stages of Spica Prunellae development. Four statistical algorithms (Delta Ct, BestKeeper, NormFinder, and geNorm) were utilized to identify the RGs' stability, and an integrated stability rating was generated via the RefFinder website online. The final ranking results revealed that eIF-2 was the most stable RG, whereas VAB2 was the least suitable as an RG. Furthermore, eIF-2 + Histon3.3 was identified as the best RG combination in different periods and the total samples. Finally, the expressions of the PvTAT and Pv4CL2 genes related to the regulation of rosmarinic acid synthesis in different organs were used to verify the stable and unstable RGs. The stable RGs in P. vulgaris were originally identified and verified in this work. This achievement provides strong support for obtaining a reliable qPCR analysis and lays the foundation for in-depth research on the developmental mechanism of Spica Prunellae.

Evaluation of candidate reference genes for quantitative RTqPCR analysis in goldfish (Carassius auratus L.) in healthy and CyHV-2 infected fish

The accuracy of quantitative real time PCR (RTqPCR) can be attained only when a suitable reference gene is used. The gene expression for a particular gene may vary within different cells at different conditions. Hence, the suitability and stability of various potential reference genes have to be determined for expression studies. In this study, we have examined the potential of four different reference genes including β-Actin (ACTB), 18S ribosomal RNA (18S), glyceraldehyde-3P-dehydrogenase (GAPDH), and elongation factor 1 alpha (EF1A_A) in seven different tissues including gill, liver, kidney, spleen, heart, muscle and intestine of goldfish (Carassius auratus). The housekeeping genes were analyzed from healthy fish and in CyHV-2 challenged fish. Based upon the real time PCR results the gene expression varied among the genes and in tissues. The expression levels of the housekeeping genes were then compared and evaluated with the RefFinder web tool which analyses results using four different algorithms - BestKeeper, delta Ct, geNorm and NormFinder. EF1A_A was ranked to be the best gene in healthy fish by BestKeeper and geNorm analysis. The delta Ct and NormFinder algorithm have found 18S to be a stable gene in healthy fish but 18S was given to be least expressed in challenged fish. ACTB was also given as a stable gene by geNorm analysis in both healthy and challenged fish. Also, in CyHV-2 challenged fish, EF1A_A was identified as the best gene by all the three analysis except by BestKeeper analysis, where it has ranked GADPH as the best housekeeping gene. Expression of the four candidate reference genes differed across all tissue types tested, inferring that a thorough study of the reference genes is necessary for cross tissue comparison. These results can be further used in the immune gene response study of goldfish infected with any viral pathogen to develop better health strategies in the disease management of goldfish aquaculture.

Selection and Evaluation of Potential Reference Genes for Quantitative Real-Time PCR in Agaricus blazei Based on Transcriptome Sequencing Data

Quantitative real-time PCR (qRT-PCR) is widely used to detect gene expression due to its high sensitivity, high throughput, and convenience. The accurate choice of reference genes is required for normalization of gene expression in qRT-PCR analysis. In order to identify the optimal candidates for gene expression analysis using qRT-PCR in Agaricus blazei, we studied the potential reference genes in this economically important edible fungus. In this study, transcriptome datasets were used as source for identification of candidate reference genes. And 27 potential reference genes including 21 newly stable genes, three classical housekeeping genes, and homologous genes of three ideal reference genes in Volvariella volvacea, were screened based on transcriptome datasets of A. blazei and previous studies. The expression stability of these genes was investigated by qRT-PCR analysis and further evaluated by four software packages, geNorm, NormFinder, BestKeeper, and RefFinder. Among these candidates, α-TUB (Tubulin alpha) and Cox5a (COX5A subunit VA of cytochrome c oxidase) were revealed as the most stable in fruit body, and suitable for 5 different developmental stages. α-TUB and ATP3 (ATP3 gamma subunit of the F1 sector of mitochondrial F1F0 ATP synthase) showed the most stable expression in stipe tissues and, Uqcrc (core subunit of the ubiquinol-cytochrome c reductase complex) and PUP3 (20S proteasome subunit beta 3) performed well in pileus tissues during the process of A. blazei development, while GAPDH (glyceraldehyde-3-phosphate dehydrogenase) was among the least stable genes in all sample sets. Finally, the Ableln3 (homology of eln3 gene of Coprinus cinereus) was adopted to validate the reliability of these stable and unstable reference genes, indicating that the use of unsuitable reference genes as internal controls could change the target gene’s expression pattern. This study can provide guidance for choosing reference genes for analyzing the expression pattern of target genes and facilitate the functional genomic investigation on fruit body formation and development, as well as stipe elongation and pileus expansion in A. blazei.

Reference genes for gene expression analysis in the fungal pathogen Neonectria ditissima and their use demonstrating expression up-regulation of candidate virulence genes

European canker, caused by the necrotrophic fungal phytopathogen Neonectria ditissima, is one of the most damaging apple diseases worldwide. An understanding of the molecular basis of N. ditissima virulence is currently lacking. Identification of genes with an up-regulation of expression during infection, which are therefore probably involved in virulence, is a first step towards this understanding. Reverse transcription quantitative real-time PCR (RT-qPCR) can be used to identify these candidate virulence genes, but relies on the use of reference genes for relative gene expression data normalisation. However, no report that addresses selecting appropriate fungal reference genes for use in the N. ditissima-apple pathosystem has been published to date. In this study, eight N. ditissima genes were selected as candidate RT-qPCR reference genes for gene expression analysis. A subset of the primers (six) designed to amplify regions from these genes were specific for N. ditissima, failing to amplify PCR products with template from other fungal pathogens present in the apple orchard. The efficiency of amplification of these six primer sets was satisfactory, ranging from 81.8 to 107.53%. Analysis of expression stability when a highly pathogenic N. ditissima isolate was cultured under 10 regimes, using the statistical algorithms geNorm, NormFinder and BestKeeper, indicated that actin and myo-inositol-1-phosphate synthase (mips), or their combination, could be utilised as the most suitable reference genes for normalisation of N. ditissima gene expression. As a test case, these reference genes were used to study expression of three candidate virulence genes during a time course of infection. All three, which shared traits with fungal effector genes, had up-regulated expression in planta compared to in vitro with expression peaking between five and six weeks post inoculation (wpi). Thus, these three genes may well be involved in N. ditissima pathogenicity and are priority candidates for further functional characterization.

Selection and validation of reliable reference genes for Tolypocladium guangdongense gene expression analysis under differentially developmental stages and temperature stresses

Tolypocladium guangdongense, formerly known as Cordyceps guangdongensis, is a widely cultivated fungus of the Cordyceps s.l. species that has been investigated over the last 12 years. It has the potential to be used in a number of applications in the health and pharmaceutical industries for it has shown its high nutritional and medicinal values according to previous animal studies. qRT-PCR (quantitative reverse transcription polymerase chain reaction) is extensively used to analyze the expression pattern and molecular mechanisms of functional genes under differentially experimental conditions. The expression stability of reference genes used for normalization determines the reliability of qRT-PCR results, indicating the importance of selection and validation of reference genes before gene expression analysis. In the present study, three statistical algorithms, geNorm, NormFinder and BestKeeper, were used for analyzing the expression stability of nineteen candidate reference genes (CRGs) in T. guangdongense. Investigation were carried out under differentially experimental conditions, which included differentially developmential stages (mycelia, primordia, young and mature fruiting bodies), different carbon sources, cold and heat stresses. The results showed that histone H4 and tubulin beta chain 2 (β-tub2) were the most and least stable genes, respectively, across all the experimental samples. Moreover, analysis of individual data sets exhibited different stability and expression profiles of reference genes. The vacuolar protein sorting gene VPS was the most stable gene expressed under the differentially developmental stages and temperature stresses, whereas H4 was the most stably expressed gene under different carbon sources. Therefore, it can be proposed that VPS and H4 are the preferred reference genes for normalization of gene expression under different experimental conditions. The results of our present study will enable more accurate evaluation of gene expression in T. guangdongense using the optimal reference gene for qRT-PCR analysis.

The NADPH oxidase in Volvariella volvacea and its differential expression in response to mycelial ageing and mechanical injury

NADPH oxidases are enzymes that have been reported to generate reactive oxygen species (ROS) in animals, plants and many multicellular fungi in response to environmental stresses. Six genes of the NADPH oxidase complex components, including vvnoxa, vvnoxb, vvnoxr, vvbema, vvrac1 and vvcdc24, were identified based on the complete genomic sequence of the edible fungus Volvariella volvacea. The number of vvnoxa, vvrac1, vvbema and vvcdc24 transcripts fluctuated with ageing, and the gene expression patterns of vvnoxa, vvrac1 and vvbema were significantly positively correlated. However, the expression of vvnoxb and vvnoxr showed no significant difference during ageing. In hyphae subjected to mechanical injury stress, both O₂^- and H₂O₂ concentrations were increased. The expression of vvnoxa, vvrac1, vvbema and vvcdc24 was substantially upregulated, but vvnoxb and vvnoxr showed no response to mechanical injury stress at the transcriptional level. Additionally, the transcription of vvnoxa, vvrac1, vvbema and vvcdc24 could be repressed when the intracellular ROS were eliminated by diphenyleneiodonium (DPI) chloride and reduced glutathione (GSH) treatments. These results indicated a positive feedback loop involving NADPH oxidase and intracellular ROS, which might be the reason for the oxidative burst during injury stress.

Selection and Validation of Reference Genes for qRT-PCR in Lentinula edodes under Different Experimental Conditions

Lentinula edodes is the most consumed mushroom in Asia due to its nutritional and medicinal values, and the optimal reference gene is crucial for normalization of its gene expression analysis. Here, the expression stability of 18 candidate reference genes (CRGs) in L. edodes was analyzed by three statistical algorithms (geNorm, NormFinder and BestKeeper) under different stresses (heat, cadmium excess and Trichoderma atroviride infection), different substrates (straw, sawdust and corn stalk) and different development stages (mycelia, primordia and fruit bodies). Among the 18 CRGs, 28S, Actin and α-tub exhibited the highest expression stability in L. edodes under all conditions, while GPD, SPRYP and MSF showed the least stable expression. The best reference gene in different conditions was different. The pairwise variation values showed that two genes would be sufficient for accurate normalization under different conditions of L. edodes. This study will contribute to more accurate estimation of the gene relative expression levels under different conditions using the optimal reference gene in qRT-PCR (quantitative reverse transcription polymerase chain reaction) analysis.

Validation of reference genes for quantitative gene expression analysis in Auricularia cornea

Auricularia cornea Ehrenb., previously named A. polytricha (Mont.) Sacc, has become one of the most widely cultivated mushrooms in China. Considerable research has been conducted on its cultivation, pathogen identification, proteomics, and more. However, to the best of our knowledge, no studies have been performed on reference-gene validation in this species. Formerly, reference genes were selected for their expression levels only relied upon from others species, owing to the fact that the gene stability in this species is unknown. In this study, nine candidate genes, including tubulin alpha-1A chain (TUBA1A), β-tubulin (Btu), phosphoglucomutase (Pgm), actin 1 (Act1), protein phosphatase 2A regulatory subunit (PP2A), polyubiquitin (UBQ), glyceraldehyde-3-phosphate dehydrogenase (Gapdh), 18S ribosomal protein (18S) and 28S ribosomal protein (28S), were evaluated among different strains and developmental stages. Four algorithms (i.e., geNorm, NormFinder, BestKeeper and RefFinder) were used to analyze candidate genes. The results revealed that UBQ was the most stable reference gene, while 18S was the least stable. Despite these results, the candidate genes were largely inadequate and only two were considered suitable. Based on candidate gene stability, PP2A and UBQ were identified as a set of usable interior control genes for future analyses in this species. This is the first systematic study conducted for selecting reference genes in A. cornea, and lays the foundation for identifying genes and quantifying gene expression in this species.

Selection of Reference Genes for qRT-PCR Analysis in Lentinula edodes after Hot-Air Drying

Volatile sulfur compounds gradually develop in Lentinula edodes after hot-air drying, and many genes are involved in the generation of these sulfur compounds. The expression stability of reference genes may vary in a particular experimental treatment when analyzing their expressions by quantitative real-time polymerase chain reaction (qRT-PCR). In this study, the expression profile of 17 candidate genes was assessed in L. edodes under treatment at 50 °C for 0, 1, 2, and 3 h, and the expression stability of each reference gene was analyzed by three statistical algorithms, including geNorm, NormFinder, and BestKeeper. Results indicated that the two optimal reference genes for mycelium and fruiting body were CAC and DAHP as well as CAC and NUP, respectively. Additionally, CAC and DAHP were found to be the two most stable reference genes across the mycelium and fruiting body set. Our results will provide a genetic foundation for further research on the metabolism genes of sulfur compounds in L. edodes.