Selection of appropriate reference genes for RT-qPCR analysis under abiotic stress and hormone treatment in celery

Reference gene selection for quantitative real-time PCR analysis of Hymenopellis radicata under abiotic stress

Hymenopellis radicata (H. radicata) is an edible fungus rich in protein and mineral elements, with high edible and medical value. And reference genes suitable for normalization of qRT-PCR data from this species have not been investigated. In this study, therefore, we selected 11 housekeeping genes common in biology. The expression levels of these housekeeping genes were measured in three different tissues and six different abiotic stress treatments in mycelium. They were evaluated for expression stability using online tools. The results showed that gene ACT could be stable expressed in all samples. The expressions of genes TUB and UBQ10 are the most stable under heat stress, ACT and EF are the most stable genes under salt stress, ACT and TUB are the most stable genes under oxidation stress, RPL6 and EF are the most stable genes under pH condition, ACT and RPB2 are the most stable genes under cadmium stress, and RPB2 and UBC are the most stable genes under drought condition. ACT and PP2A are the most stable genes at different tissue sites. This study is of great help to explore the gene expression pattern of H. radicata, and also provides reference for internal reference gene screening under other conditions.

Selection of suitable reference genes for qPCR normalization in different developmental stages of Oenanthe javanica

Gene expression analysis is widely used to unravel molecular regulatory mechanisms and identify key genes in plants. Appropriate reference gene is an important prerequisite to ensure the accuracy and reliability of qPCR analysis results. Water dropwort is a plant of the Oenanthe genus in the Apiaceae family, which has high economic benefits. However, the underlying molecular regulatory mechanisms in the growth and development of water dropwort have not been fully understood and the appropriate reference genes in different developmental stages of water dropwort not yet reported. In this study, 10 candidate reference genes (ACTIN, PP2A, SAND, EF-1α, GAPDH, UBQ, MIP, TBP, RPS-18, eIF-4α) were identified and cloned from Oenanthe javanica. The qPCR primers of candidate reference genes were designed and verified. Four statistical algorithms, geNorm, NormFinder, BestKeeper and RefFinder were used to evaluate the expression stability of 10 candidate reference genes in different developmental stages of water dropwort. The results showed that TBP and UBQ were the most stable genes in different developmental stages of water dropwort, while GAPDH was the most unstable gene. The normalization of EXP1 genes at different developmental stages further confirmed the reliability of internal reference genes. The results of this study provide a theoretical basis for selecting appropriate internal reference genes in different developmental stages of water dropwort. This study also provides technical support and reliable basis for the expression analysis of key genes in different developmental stages of water dropwort.

Reference Genes Screening and Gene Expression Patterns Analysis Involved in Gelsenicine Biosynthesis under Different Hormone Treatments in Gelsemium elegans

Reverse transcription quantitative polymerase chain reaction (RT-qPCR) is an accurate method for quantifying gene expression levels. Choosing appropriate reference genes to normalize the data is essential for reducing errors. Gelsemium elegans is a highly poisonous but important medicinal plant used for analgesic and anti-swelling purposes. Gelsenicine is one of the vital active ingredients, and its biosynthesis pathway remains to be determined. In this study, G. elegans leaf tissue with and without the application of one of four hormones (SA, MeJA, ETH, and ABA) known to affect gelsenicine synthesis, was analyzed using ten candidate reference genes. The gene stability was evaluated using GeNorm, NormFinder, BestKeeper, ∆CT, and RefFinder. The results showed that the optimal stable reference genes varied among the different treatments and that at least two reference genes were required for accurate quantification. The expression patterns of 15 genes related to the gelsenicine upstream biosynthesis pathway was determined by RT-qPCR using the relevant reference genes identified. Three genes 8-HGO, LAMT, and STR, were found to have a strong correlation with the amount of gelsenicine measured in the different samples. This research is the first study to examine the reference genes of G. elegans under different hormone treatments and will be useful for future molecular analyses of this medically important plant species.

Selection of Suitable Reference Genes for RT-qPCR Gene Expression Analysis in Centipedegrass under Different Abiotic Stress

As a C4 warm-season turfgrass, centipedegrass (Eremochloa ophiuroides (Munro) Hack.) is known for its exceptional resilience to intensive maintenance practices. In this research, the most stably expressed reference genes in the leaves of centipedegrass under different stress treatments, including salt, cold, drought, aluminum (Al), and herbicide, were screened by the quantitative real-time PCR (RT-qPCR) technique. The stability of 13 candidate reference genes was evaluated by software GeNorm V3.4, NormFinder V20, BestKeeper V1.0, and ReFinder V1.0. The results of this experiment demonstrated that the expression of the UBC (ubiquitin-conjugating enzyme) remained the most stable under cold and Al stress conditions. On the other hand, the MD (malate dehydrogenase) gene exhibited the best performance in leaf tissues subjected to salt and drought stresses. Under herbicide stress, the expression level of the RIP (60S ribosomal protein L2) gene ranked the highest. The expression levels of abiotic stress-associated genes such as PIP1, PAL, COR413, ALMT9, and BAR were assessed to validate the reliability of the selected reference genes. This study provides valuable information and reference points for gene expression under abiotic stress conditions in centipedegrass.

Plastid DNA Barcoding and RtActin cDNA Fragment Isolation of Reutealis Trisperma: A Promising Bioresource for Biodiesel Production

Reutealis trisperma belonging to the family Euphorbiaceae is currently used for biodiesel production, and rapid development in plant-based biofuel production has led to its increasing demand. However, massive utilization of bio-industrial plants has led to conservation issues. Moreover, genetic information on R trisperma is still limited, which is crucial for developmental, physiological, and molecular studies. Studying gene expression is essential to explain plant physiological processes. Nonetheless, this technique requires sensitive and precise measurement of messenger RNA (mRNA). In addition, the presence of internal control genes is important to avoid bias. Therefore, collecting and preserving genetic data for R trisperma is indispensable. In this study, we aimed to evaluate the application of plastid loci, rbcL, and matK, to the DNA barcode of R trisperma for use in conservation programs. In addition, we isolated and cloned the RtActin (RtACT) gene fragment for use in gene expression studies. Sequence information was analyzed in silico by comparison with other Euphorbiaceae plants. For actin fragment isolation, reverse-transcription polymerase chain reaction was used. Molecular cloning of RtActin was performed using the pTA2 plasmid before sequencing. We successfully isolated and cloned 592 and 840 bp of RtrbcL and RtmatK fragment genes, respectively. The RtrbcL barcoding marker, rather than the RtmatK plastidial marker, provided discriminative molecular phylogenetic data for R Trisperma. We also isolated 986 bp of RtACT gene fragments. Our phylogenetic analysis demonstrated that R trisperma is closely related to the Vernicia fordii Actin gene (97% identity). Our results suggest that RtrbcL could be further developed and used as a barcoding marker for R trisperma. Moreover, the RtACT gene could be further investigated for use in gene expression studies of plant.

AgMYB5, an MYB transcription factor from celery, enhanced β-carotene synthesis and promoted drought tolerance in transgenic Arabidopsis

BACKGROUND

Water shortage caused by global warming seriously affects the yield and quality of vegetable crops. β-carotene, the lipid-soluble natural product with important pharmacological value, is abundant in celery. Transcription factor MYB family extensively disperses in plants and plays regulatory roles in carotenoid metabolism and water scarcity response.

RESULTS

Here, the AgMYB5 gene encoding 196 amino acids was amplified from celery cv. 'Jinnanshiqin'. In celery, the expression of AgMYB5 exhibited transactivation activity, tissue specificity, and drought-condition responsiveness. Further analysis proved that ectopic expression of AgMYB5 increased β-carotene content and promoted drought tolerance in transgenic Arabidopsis thaliana. Moreover, AgMYB5 expression promoted β-carotene biosynthesis by triggering the expression of AtCRTISO and AtLCYB, which in turn increased antioxidant enzyme activities, and led to the decreased contents of H₂O₂ and MDA, and the inhibition of O₂^- generation. Meanwhile, β-carotene accumulation promoted endogenous ABA biosynthesis of transgenic Arabidopsis, which resulted in ABA-induced stomatal closing and delayed water loss. In addition, ectopic expression of AgMYB5 increased expression levels of AtERD1, AtP5CS1, AtRD22, and AtRD29.

CONCLUSIONS

The findings indicated that AgMYB5 up-regulated β-carotene biosynthesis and drought tolerance of Arabidopsis.

Reference genes selection of Paeonia ostii 'Fengdan' under osmotic stresses and hormone treatments by RT-qPCR

BACKGROUND

Tree peony possess significant ornamental, medicinal and oil values. Osmotic stresses including dehydratiuon and salinity limit the expansion of cultivation area of tree peony. Information on reference genes selection under osmotic stress and hormone stimulation of tree peony still limited. This study aimed to determine the stable reference genes suitable for tree peony under osmotic stresses and hormone treatments, and provide a theoretical basis for the molecular biology research.

METHODS AND RESULTS

Twelve candidate reference genes were evaluated in Paeonia ostii 'Fengdan' under osmotic stress and hormone treatments by RT-qPCR. Delta Ct method, geNorm, and NormFinder were used for the comprehensive expression stability ranking comparison. The results revealed that tubulin-α was the preferred internal reference genes for drought and ABA treatment, tubulin-β was identified as the most suitable reference gene under drought and OPDA induction, 18s-rRNA was regarded as the most stable gene for salinity and JA treatment, eIF-5 A was listed as the most stable gene for JA and MeJA treatments. The experiments also displayed that EF1-α were comparatively unstable under ABA and BR hormone treatments.

CONCLUSION

These preferred reference genes could be useful in qPCR studies involving osmotic or hormonal stresses in Paeonia ostii 'Fengdan'. It is anticipated that the results will benefit tree peony functional genomics studies and molecular breeding research in the future.

Selection and validation of appropriate reference genes for RT-qPCR analysis of Nitraria sibirica under various abiotic stresses

BACKGROUND

Nitraria sibirica Pall. is a halophytic shrub with strong environmental adaptability that can survive in extremely saline-alkali and drought-impacted environments. Gene expression analysis aids in the exploration of the molecular mechanisms of plant responses to abiotic stresses. RT-qPCR is the most common technique for studying gene expression. Stable reference genes are a prerequisite for obtaining accurate target gene expression results in RT-qPCR analysis.

RESULTS

In this study, a total of 10 candidate reference genes were selected from the transcriptome of N. sibirica, and their expression stability in leaves and roots under different treatment conditions (salt, alkali, drought, cold, heat and ABA) was evaluated with the geNorm, NormFinder, BestKeeper, comparative ΔCt and RefFinder programs. The results showed that the expression stability of the candidate reference genes was dependent on the tissue and experimental conditions tested. ACT7 combined with R3H, GAPDH, TUB or His were the most stable reference genes in the salt- or alkali-treated leaves, salt-treated roots and drought-treated roots, respectively; R3H and GAPDH were the most suitable combination for drought-treated leaves, heat-treated root samples and ABA-treated leaves; DIM1 and His maintained stable expression in roots under alkali stress; and TUB combined with R3H was stable in ABA-treated roots. TBCB and GAPDH exhibited stable expression in heat-treated leaves; TBCB, R3H, and ERF3A were stable in cold-treated leaves; and the three most stable reference genes for cold-treated roots were TBCB, ACT11 and DIM1. The reliability of the selected reference genes was further confirmed by evaluating the expression patterns of the NsP5CS gene under the six treatment conditions.

CONCLUSION

This study provides a theoretical reference for N. sibirica gene expression standardization and quantification under various abiotic stress conditions and will help to reveal the molecular mechanisms that confer stress tolerance to N. sibirica.

Structural and functional analysis of stress-inducible genes and their promoters selected from young oil palm (Elaeis guineensis) under salt stress

Background

Soil salinity is a problem in more than 100 countries across all continents. It is one of the abiotic stress that threatens agriculture the most, negatively affecting crops and reducing productivity. Transcriptomics is a technology applied to characterize the transcriptome in a cell, tissue, or organism at a given time via RNA-Seq, also known as full-transcriptome shotgun sequencing. This technology allows the identification of most genes expressed at a particular stage, and different isoforms are separated and transcript expression levels measured. Once determined by this technology, the expression profile of a gene must undergo validation by another, such as quantitative real-time PCR (qRT-PCR). This study aimed to select, annotate, and validate stress-inducible genes—and their promoters—differentially expressed in the leaves of oil palm (Elaeis guineensis) plants under saline stress.

Results

The transcriptome analysis led to the selection of 14 genes that underwent structural and functional annotation, besides having their expression validated using the qRT-PCR technique. When compared, the RNA-Seq and qRT-PCR profiles of those genes resulted in some inconsistencies. The structural and functional annotation analysis of proteins coded by the selected genes showed that some of them are orthologs of genes reported as conferring resistance to salinity in other species. There were those coding for proteins related to the transport of salt into and out of cells, transcriptional regulatory activity, and opening and closing of stomata. The annotation analysis performed on the promoter sequence revealed 22 distinct types of cis-acting elements, and 14 of them are known to be involved in abiotic stress.

Conclusion

This study has helped validate the process of an accurate selection of genes responsive to salt stress with a specific and predefined expression profile and their promoter sequence. Its results also can be used in molecular-genetics-assisted breeding programs. In addition, using the identified genes is a window of opportunity for strategies trying to relieve the damages arising from the salt stress in many glycophyte crops with economic importance.

Comparative metabolomics provides novel insights into the basis of petiole color differences in celery (Apiumgraveolens L.)

Plant metabolites are important for plant development and human health. Plants of celery (Apiumgraveolens L.) with different-colored petioles have been formed in the course of long-term evolution. However, the composition, content distribution, and mechanisms of accumulation of metabolites in different-colored petioles remain elusive. Using ultra-high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS), 1159 metabolites, including 100 lipids, 72 organic acids and derivatives, 83 phenylpropanoids and polyketides, and several alkaloids and terpenoids, were quantified in four celery cultivars, each with a different petiole color. There were significant differences in the types and contents of metabolites in celery with different-colored petioles, with the most striking difference between green celery and purple celery, followed by white celery and green celery. Annotated analysis of metabolic pathways showed that the metabolites of the different-colored petioles were significantly enriched in biosynthetic pathways such as anthocyanin, flavonoid, and chlorophyll pathways, suggesting that these metabolic pathways may play a key role in determining petiole color in celery. The content of chlorophyll in green celery was significantly higher than that in other celery cultivars, yellow celery was rich in carotenoids, and the content of anthocyanin in purple celery was significantly higher than that in the other celery cultivars. The color of the celery petioles was significantly correlated with the content of related metabolites. Among the four celery cultivars, the metabolites of the anthocyanin biosynthesis pathway were enriched in purple celery. The results of quantitative real-time polymerase chain reaction (qRT-PCR) suggested that the differential expression of the chalcone synthase (CHS) gene in the anthocyanin biosynthesis pathway might affect the biosynthesis of anthocyanin in celery. In addition, HPLC analysis revealed that cyanidin is the main pigment in purple celery. This study explored the differences in the types and contents of metabolites in celery cultivars with different-colored petioles and identified key substances for color formation. The results provide a theoretical basis and technical support for genetic improvement of celery petiole color.

Selection and Validation of Reliable Reference Genes for Gene Expression Studies in Different Genotypes and TRV-Infected Fruits of Peach (Prunus persica L. Batsch) during Ripening

Real-time quantitative PCR (RT-qPCR) is a powerful tool to detect and quantify transcription abundance, and the stability of the reference gene determines its success. However, the most suitable reference gene for different genotypes and tobacco rattle virus (TRV) infected fruits was unclear in peach (Prunus persica L. Batsch). In this study, 10 reference genes were selected and gene expression was characterized by RT-qPCR across all samples, including different genotypes and TRV-infected fruits during ripening. Four statistical algorithms (geNorm, NormFinder, BestKeeper, and RefFinder) were used to calculate the stability of 10 reference genes. The geNorm analysis indicated that two suitable reference genes should be used for gene expression normalization. In general, the best combination of reference genes was CYP2 and Tua5 for TRV-infected fruits and CYP2 and Tub1 for different genotypes. In 18S, GADPH, and TEF2, there is an unacceptable variability of gene expression in all experimental conditions. Furthermore, to confirm the validity of the reference genes, the expression levels of PpACO1, PpEIN2, and PpPL were normalized at different fruit storage periods. In summary, our results provide guidelines for selecting reliable reference genes in different genotypes and TRV-infected fruits and lay the foundation for accurate evaluation of gene expression for RT-qPCR analysis in peach.

AgMYB12, a novel R2R3-MYB transcription factor, regulates apigenin biosynthesis by interacting with the AgFNS gene in celery

Overexpression of AgMYB12 in celery improved the accumulation of apigenin by interacting with the AgFNS gene. Celery is a common vegetable, and its essential characteristic is medicine food homology. A natural flavonoid and a major pharmacological component in celery, apigenin plays an important role in human health. In this study, we isolated a novel R2R3-MYB transcription factor that regulates apigenin accumulation from the celery cultivar 'Jinnan Shiqin' through yeast one-hybrid screening and designated it as AgMYB12. The AgMYB12 protein was located in the nucleus. It showed transcriptional activation activity and bound specifically to the promoter of AgFNS, a gene involved in apigenin biosynthesis. Phylogenetic tree analysis demonstrated that AgMYB12 belongs to the flavonoid branch. It contains two flavonoid-related motifs, SG7 and SG7-2, and shared a highly conserved R2R3 domain with flavonoid-related MYBs. The homologous overexpression of AgMYB12 induced the up-regulation of AgFNS gene expression and accumulation of apigenin and luteolin in celery. Additionally, the expression levels of apigenin biosynthesis-related genes, including AgPAL, AgCHI, AgCHS, Ag4CL, and AgC4H, increased in transgenic celery plants. These results indicated that AgMYB12 acted as a positive regulator of apigenin biosynthesis and activated the expression of AgFNS gene. The current study provides new information about the regulation mechanism of apigenin metabolism in celery and offers a strategy for cultivating the plants with high apigenin content.

AgZDS, a gene encoding ζ-carotene desaturase, increases lutein and β-carotene contents in transgenic Arabidopsis and celery

ζ-Carotene desaturase (ZDS) is one of the key enzymes regulating carotenoids biosynthesis and accumulation. Celery transgenic efficiency is low and it is difficult to obtain transgenic plants. The study on ZDS was limited in celery. Here, the AgZDS gene was cloned from celery and overexpressed in Arabidopsis thaliana and celery to verify its function. The AgZDS has typical characteristic of ZDS protein and is highly conserved in higher plants. Phylogenetic analysis showed that AgZDS has the closest evolutionary relationship with ZDSs from Solanum lycopersicum, Capsicum annuum and Tagetes erecta. Overexpression of AgZDS gene in A. thaliana and celery resulted in increased accumulations of lutein and β-carotene and up-regulated the expression levels of the genes involved in carotenoids biosynthesis. The contents of lutein and β-carotene in two lines, AtL1 and AgL5, were the highest in transgenic A. thaliana and celery, respectively. The relative expression levels of 5 genes (AtPDS, AtZISO, AtZEP, AtNCED3, and AtCCD4) were up-regulated compared to the wild type plants. The relative expression levels of most genes in carotenoids biosynthesis pathway, such as AgPDS, AgCRTISO1, and AgZISO, were up-regulated in transgenic celery plants. The antioxidant capacity of A. thaliana and photosynthetic capacity of celery were also enhanced. This research is the first report on the function of structure gene related to carotenoid biosynthesis in transgenic celery plants. The findings in this study demonstrated the roles of AgZDS in regulating carotenoids metabolism of celery, which laid a potential foundation for quality improvement of celery.

Identification of reliable reference genes for quantitative real-time PCR analysis of the Rhus chinensis Mill. leaf response to temperature changes

Rhus chinensis Mill. (RCM) is the host plant of Galla chinensis, which is valued in traditional medicine. Environmental temperature directly determines the probability of gallnut formation and RCM growth. At present, there is no experiment to systematically analyse the stability of internal reference gene (RG) expression in RCM. In this experiment, leaves that did not form gallnuts were used as the control group, while leaves that formed gallnuts were used as the experimental group. First, we conducted transcriptome experiments on RCM leaves to obtain 45 103 differential genes and functional enrichment annotations between the two groups. On this basis, this experiment established a transcriptional gene change model of leaves in the process of gallnut formation after being bitten by aphids, and RCM reference candidate genes were screened from RNA sequencing (RNA‐seq) data. This study is based on RCM transcriptome data and evaluates the stability of 11 potential reference genes under cold stress (4 °C) and heat stress (34 °C), using three statistical algorithms (geNorm, NormFinder, and BestKeeper). The results show that GAPDH1 + PP2A2/UBQ are stable reference genes under heat stress, while GAPDH1 + ACT are the most stable under cold stress. This study is the first to screen candidate reference genes in RCM and could help guide future molecular studies in this genus.

Selection and evaluation of reference genes for qRT-PCR of Scutellaria baicalensis Georgi under different experimental conditions

Scutellaria baicalensis Georgi is a famous medicinal plant with its dried roots having been used as a traditional Chinese medicinal for more than 2000 years. Although its genome sequence has previously been published and molecular biology methods have been used to study this species, no suitable internal reference genes have been investigated for standardization of gene expression via quantitative real-time polymerase chain reaction (qRT-PCR). Here, the stabilities of 10 candidate reference genes, ACT11, ACT7, α-TUB, β-TUB, GAPDH, UBC, RPL, SAM, HSP70, and PP2A, were analyzed by four different procedures of GeNorm, NormFinder, BestKeeper, and RefFinder. Their expression stabilities were evaluated under various conditions, including different tissue types (root, stem, leaf, and flower), hormone stimuli treatments (methyl jasmonate, salicylic acid, and abscisic acid), and abiotic stresses (heavy metal, salt, drought, cold, and wounding). The results indicated that β-TUB was the most stable gene for all tested samples, while ACT11 was the most unstable. The most stable reference gene was not consistent under different conditions. β-TUB exhibited the highest stability for different tissue types and abiotic stresses, while for hormone stimuli treatments, ACT7 showed the highest stability. To confirm the applicability of suitable reference genes, we selected to SbF6H and SbF8H as target genes to analyze their expression levels in different tissues. This study helps to the accurate quantification of the relative expression levels of interest genes in S. baicalensis via qRT-PCR analysis.

The gene encoding lycopene epsilon cyclase of celery enhanced lutein and β-carotene contents and confers increased salt tolerance in Arabidopsis

Celery (Apium graveolens L.) is a leafy vegetable of Apiaceae, which is greatly popular because of its rich nutrients. Lutein and β-carotene are two important carotenoids. Lycopene epsilon cyclase (LCY-ε) is a key branch point enzyme in the carotenoid biosynthetic pathway. In this study, we cloned the AgLCY-ε gene from celery and overexpressed it in Arabidopsis. The results showed that both lutein and β-carotene accumulation increased significantly in transgenic Arabidopsis hosting AgLCY-ε gene, compared with wild type (WT) plants. The transcription levels of AtPSY and AtCRTISO genes involved in carotenoids biosynthesis also increased in transgenic lines. One-month-old transgenic Arabidopsis seedlings were treated with 200 mM NaCl. The malondialdehyde (MDA) content in transgenic Arabidopsis plants after salt treatment was significantly lower, and the activities of the two antioxidant enzymes, superoxide dismutase (SOD) and peroxidase (POD), were significantly increased than that of WT plants. Overexpression of AgLCY-ε gene showed increased lutein and β-carotene accumulations, and enhanced salt tolerance in transgenic plants.

Carex muskingumensis and Osmotic Stress: Identification of Reference Genes for Transcriptional Profiling by RT-qPCR

Carex muskingumensis is a highly valued perennial ornamental grass cultivated worldwide. However, there is limited genetic data regarding this species. Selection of proper reference genes (RGs) for reverse transcription quantitative PCR (RT-qPCR) data normalization has become an essential step in gene expression analysis. In this study, we aimed to examine expression stability of nine candidate RGs in C. muskingumensis plants, subjected to osmotic stress, generated either by salinity or PEG treatment. The identification of genes exhibiting high expression stability was performed by four algorithms (geNorm, NormFinder, BestKeeper and deltaCt method). The results showed that the combination of two genes would be sufficient for reliable expression data normalization. ADP (ADP-ribosylation factor) and TBP (TATA-box-binding protein) were identified as the most stably expressed under salinity treatment, while eIF4A (eukaryotic initiation factor 4A) and TBP were found to show the highest stability under PEG-induced drought. A set of three genes (ADP, eIF4A and TBP) displayed the highest expression stability across all experimental samples tested in this study. To our best knowledge, this is the first report regarding RGs selection in C. muskingumensis. It will provide valuable starting point information for conducting further analyses in this and related species concerning their responses to water shortage and salinity stress.

Transcriptome-based selection and validation of optimal house-keeping genes for skin research in goats (Capra hircus)

BACKGROUND

In quantitative real-time polymerase chain reaction (qRT-PCR) experiments, accurate and reliable target gene expression results are dependent on optimal amplification of house-keeping genes (HKGs). RNA-seq technology offers a novel approach to detect new HKGs with improved stability. Goat (Capra hircus) is an economically important livestock species and plays an indispensable role in the world animal fiber and meat industry. Unfortunately, uniform and reliable HKGs for skin research have not been identified in goat. Therefore, this study seeks to identify a set of stable HKGs for the skin tissue of C. hircus using high-throughput sequencing technology.

RESULTS

Based on the transcriptome dataset of 39 goat skin tissue samples, 8 genes (SRP68, NCBP3, RRAGA, EIF4H, CTBP2, PTPRA, CNBP, and EEF2) with relatively stable expression levels were identified and selected as new candidate HKGs. Commonly used HKGs including SDHA and YWHAZ from a previous study, and 2 conventional genes (ACTB and GAPDH) were also examined. Four different experimental variables: (1) different development stages, (2) hair follicle cycle stages, (3) breeds, and (4) sampling sites were used for determination and validation. Four algorithms (geNorm, NormFinder, BestKeeper, and ΔCt method) and a comprehensive algorithm (ComprFinder, developed in-house) were used to assess the stability of each HKG. It was shown that NCBP3 + SDHA + PTPRA were more stably expressed than previously used genes in all conditions analysis, and that this combination was effective at normalizing target gene expression. Moreover, a new algorithm for comprehensive analysis, ComprFinder, was developed and released.

CONCLUSION

This study presents the first list of candidate HKGs for C. hircus skin tissues based on an RNA-seq dataset. We propose that the NCBP3 + SDHA + PTPRA combination could be regarded as a triplet set of HKGs in skin molecular biology experiments in C. hircus and other closely related species. In addition, we also encourage researchers who perform candidate HKG evaluations and who require comprehensive analysis to adopt our new algorithm, ComprFinder.

Selection of suitable reference genes for qRT-PCR expression analysis of Codonopsis pilosula under different experimental conditions

Codonopsis pilosula is a well-known medicinal plant. Although its transcriptome sequence has been published, suitable reference genes have not been systematically identified for conducting expression analyses via quantitative real-time polymerase chain reaction (qRT-PCR). To screen appropriate genes for use with this species, we applied four different methods-GeNorm, NormFinder, BestKeeper, and RefFinder-to evaluate the stability of 13 candidates: CpiEF1Bb, CpiCACS, CpiF-Box, Cpiβ-Tubulin, CpiGAPDH, CpiActin2, CpiAPT1, CpiActin7, CpiActin8, CpiRPL6, CpiHAF1, CpiTubulin6, and CpiUBQ12. Expression was examined by qRT-PCR for various tissue types, chemical treatments, and developmental stages. For all tested samples, CpiGAPDH proved to be the most stable. Comprehensive analysis indicated that the most stable internal reference genes were CpiF-Box and CpiCACS in different tissues and at different developmental stages, respectively. Under NaCl stress, CpiAPT1 was the best internal reference gene. For methyl jasmonate and abscisic acid treatments, CpiGAPDH and CpiF-Box, respectively, presented the highest degree of expression stability. Based on these findings, we chose CpiSPL9 as the target gene for validating the suitability of these selected reference genes. All of these results provide a foundation for accurate quantification of expression levels by genes of interest in C. pilosula.

Identification and evaluation of reference genes for quantitative real-time PCR analysis in Passiflora edulis under stem rot condition

Passion fruit (Passiflora edulis), an important tropical and subtropical fruit, has a high edible and medicinal value. Stem rot disease is one of the most important diseases of passion fruit. An effective way for control and prevention of this disease is to identify the genes associated with resistance to this disease. Quantitative real-time PCR (RT-qPCR) has mainly been widely applied to detect gene expression because of its simplicity, fastness, low cost and high sensitivity. One of the requirements for RT-qPCR is the availability of suitable reference genes for normalization of gene expression. However, currently, no Passiflora edulis reference genes have been identified andthus it has hindered the gene expression studies in this plant. The present study aimed to address this issue. We analyzed sixteen candidate reference genes, including nine common (GAPDH, UBQ, ACT1, ACT2, EF-1α-1, EF-1α-2, TUA, NADP, and GBP) and seven novel genes (C13615, C24590, C27182, C10445, C21209, C22199, and C22526), in different tissues (stem, leaf, flower and fruit) of two accessions under stem rot condition. We calculated the expression stability in twenty-four samples using the ΔCt, GeNorm, NormFinder, BestKeeper and RefFinder. The results showed that both C21209 and EF-1α-2 were sufficient to normalize gene expression under stem rot, whereas the commonly used reference genes, GAPDH and UBQ, were the least stable ones. The expression patterns of PeUFC under stem rot condition normalized by stable and unstable reference genes indicated the suitability of using the optimal reference genes. To our knowledge, this is the first systematic study of reference genes in Passiflora edulis, which identified a number of reliable reference genes suitable for gene expression studies in Passiflora edulis by RT-qPCR.