Molecular characterization and spatial expression of the sunflower ABP1 gene

Screening and Verification of Reference Genes for Analysis of Gene Expression in Garlic (Allium sativum L.) under Cold and Drought Stress

The principal objective of this study was to screen and verify reference genes appropriate for gene expression evaluation during plant growth and development under distinct growth conditions. Nine candidate reference genes were screened based on garlic transcriptome sequence data. RT-qPCR was used to detect the expression levels of the aforementioned reference genes in specific tissues under drought and cold stress. Then, geNorm, NormFinder, BestKeeper, and ReFinder were used to consider the consistency of the expression levels of candidate reference genes. Finally, the stress-responsive gene expression of ascorbate peroxidase (APX) was quantitatively evaluated to confirm the chosen reference genes. Our results indicated that there were variations in the abundance and stability of nine reference gene transcripts underneath cold and drought stress, among which ACT and UBC-E2 had the highest transcript abundance, and 18S rRNA and HIS3 had the lowest transcript abundance. UBC and UBC-E2 were the most stably expressed genes throughout all samples; UBC and UBC-E2 were the most stably expressed genes during cold stress, and ACT and UBC were the most stably expressed genes under drought stress. The most stably expressed genes in roots, pseudostems, leaves, and cloves were EF1, ACT, HIS3, UBC, and UBC-E2, respectively, while GAPDH was the most unstable gene during drought and cold stress conditions and in exclusive tissues. Taking the steady reference genes UBC-E2, UBC, and ACT as references during drought and cold stress, the reliability of the expression levels was further demonstrated by detecting the expression of AsAPX. Our work thereby offers a theoretical reference for the evaluation of gene expression in garlic in various tissues and under stress conditions.

Reduced translocation in 2,4-D-resistant oriental mustard populations (Sisymbrium orientale L.) from Australia

BACKGROUND

Two oriental mustard populations (P2 and P13) collected from Port Broughton, South Australia were identified as resistant to 2,4-D. The level of resistance, mechanism and the mode of inheritance for 2,4-D resistance in these populations were investigated.

RESULTS

Populations P2 and P13 were confirmed to be resistant to 2,4-D at the field rate (600 g a.e. ha^-1 ). P2 and P13 were 81- and 67-fold more resistant than the susceptible populations (S1 and S2) at the dose required for 50% mortality (LD₅₀ ), respectively. No predicted amino acid modification was detected in sequences of potential target-site genes (ABP, TIR1 and AFB5). Resistant populations had reduced 2,4-D translocation compared with the susceptible populations, with 77% of [¹⁴ C]2,4-D retained in the treated leaf versus 32% at 72 h after treatment. Resistance to 2,4-D is encoded on the nuclear genome and is dominant, as the response to 2,4-D of all F₂ individuals were similar to the resistant biotypes. The segregation of F₂ phenotypes fitted a 3: 1 (R: S) inheritance model.

CONCLUSION

Resistance to 2,4-D in oriental mustard is likely due to reduced translocation of 2,4-D out of the treated leaf. Inheritance of 2,4-D resistance is conferred by a single gene with a high level of dominance. © 2017 Society of Chemical Industry.

Tobacco rattle virus (TRV)-Mediated Silencing of Nicotiana benthamiana ARGONAUTES (NbAGOs) Reveals New Antiviral Candidates and Dominant Effects of TRV-NbAGO1

The objective of this study was to determine the contribution of different ARGONAUTE proteins in Nicotiana benthamiana (NbAGOs) to the defense against silencing sensitive GFP-expressing viral constructs based on Tomato bushy stunt virus (TBSV) (Tombusvirus), Sunn-hemp mosaic virus (Tobamovirus), and Foxtail mosaic virus (Potexvirus). Upon Tobacco rattle virus (TRV)-mediated down-regulation of NbAGO1, 4, 5, or 6, no effects were noted on susceptibility to any virus construct, whereas knockdown of NbAGO2 specifically prevented silencing of P19-defective TBSV (TGdP19). Down-regulation of a new gene referred to as NbAGO5L showed some reduced silencing for TGdP19 but not for the other two virus constructs, whereas silencing of NbAGO7 gave rise to a subtle increase in susceptibility to all three viruses. Co-infiltrating different TRV-NbAGO constructs simultaneously did not enhance virus susceptibility. However, an unexpected finding was that whenever the TRV-NbAGO1 construct was present, this compromised silencing of genes targeted by co-infiltrated constructs, as shown upon co-infiltration of TRV-NbAGO1 with either TRV-NbAGO2 or TRV-Sul (targeting Magnesium chelatase I). Only after a prolonged period (approximately 2 months) did TRV-Sul-mediated systemic bleaching occur in these co-infected plants, suggesting that TRV-NbAGO1 hinders the silencing ability of other TRV-NbAGO constructs. In conclusion, this study revealed new antiviral NbAGOs and dominant effects of silencing NbAGO1.

Functional characterization of AGAMOUS-subfamily members from cotton during reproductive development and in response to plant hormones

Expression analysis of the AG -subfamily members from G. hirsutum during flower and fruit development. Reproductive development in cotton, including the fruit and fiber formation, is a complex process; it involves the coordinated action of gene expression regulators, and it is highly influenced by plant hormones. Several studies have reported the identification and expression of the transcription factor family MADS-box members in cotton ovules and fibers; however, their roles are still elusive during the reproductive development in cotton. In this study, we evaluated the expression profiles of five MADS-box genes (GhMADS3, GhMADS4, GhMADS5, GhMADS6 and GhMADS7) belonging to the AGAMOUS-subfamily in Gossypium hirsutum. Phylogenetic and protein sequence analyses were performed using diploid (G. arboreum, G. raimondii) and tetraploid (G. barbadense, G. hirsutum) cotton genomes, as well as the AG-subfamily members from Arabidopsis thaliana, Petunia hybrida and Antirrhinum majus. qPCR analysis showed that the AG-subfamily genes had high expression during flower and fruit development in G. hirsutum. In situ hybridization analysis also substantiates the involvement of AG-subfamily members on reproductive tissues of G. hirsutum, including ovule and ovary. The effect of plant hormones on AG-subfamily genes expression was verified in cotton fruits treated with gibberellin, auxin and brassinosteroid. All the genes were significantly regulated in response to auxin, whereas only GhMADS3, GhMADS4 and GhMADS7 genes were also regulated by brassinosteroid treatment. In addition, we have investigated the GhMADS3 and GhMADS4 overexpression effects in Arabidopsis plants. Interestingly, the transgenic plants from both cotton AG-like genes in Arabidopsis significantly altered the fruit size compared to the control plants. This alteration suggests that cotton AG-like genes might act regulating fruit formation. Our results demonstrate that members of the AG-subfamily in G. hirsutum present a conserved expression profile during flower development, but also demonstrate their expression during fruit development and in response to phytohormones.

Reliable Selection and Holistic Stability Evaluation of Reference Genes for Rice Under 22 Different Experimental Conditions

Stable and uniform expression of reference genes across samples plays a key role in accurate normalization of gene expression by reverse-transcription quantitative polymerase chain reaction (RT-qPCR). For rice study, there is still a lack of validation and recommendation of appropriate reference genes with high stability depending on experimental conditions. Eleven candidate reference genes potentially owning high stability were evaluated by geNorm and NormFinder for their expression stability in 22 various experimental conditions. Best combinations of multiple reference genes were recommended depending on experimental conditions, and the holistic stability of reference genes was also evaluated. Reference genes would become more variable and thus needed to be critically selected in experimental groups of tissues, heat, 6-benzylamino purine, and drought, but they were comparatively stable under cold, wound, and ultraviolet-B stresses. Triosephosphate isomerase (TI), profilin-2 (Profilin-2), ubiquitin-conjugating enzyme E2 (UBC), endothelial differentiation factor (Edf), and ADP-ribosylation factor (ARF) were stable in most of our experimental conditions. No universal reference gene showed good stability in all experimental conditions. To get accurate expression result, suitable combination of multiple reference genes for a specific experimental condition would be a better choice. This study provided an application guideline to select stable reference genes for rice gene expression study.

Validation of reference genes aiming accurate normalization of qRT-PCR data in Dendrocalamus latiflorus Munro

BACKGROUND

Dendrocalamus latiflorus Munro distributes widely in subtropical areas and plays vital roles as valuable natural resources. The transcriptome sequencing for D. latiflorus Munro has been performed and numerous genes especially those predicted to be unique to D. latiflorus Munro were revealed. qRT-PCR has become a feasible approach to uncover gene expression profiling, and the accuracy and reliability of the results obtained depends upon the proper selection of stable reference genes for accurate normalization. Therefore, a set of suitable internal controls should be validated for D. latiflorus Munro.

RESULTS

In this report, twelve candidate reference genes were selected and the assessment of gene expression stability was performed in ten tissue samples and four leaf samples from seedlings and anther-regenerated plants of different ploidy. The PCR amplification efficiency was estimated, and the candidate genes were ranked according to their expression stability using three software packages: geNorm, NormFinder and Bestkeeper. GAPDH and EF1α were characterized to be the most stable genes among different tissues or in all the sample pools, while CYP showed low expression stability. RPL3 had the optimal performance among four leaf samples. The application of verified reference genes was illustrated by analyzing ferritin and laccase expression profiles among different experimental sets. The analysis revealed the biological variation in ferritin and laccase transcript expression among the tissues studied and the individual plants.

CONCLUSIONS

geNorm, NormFinder, and BestKeeper analyses recommended different suitable reference gene(s) for normalization according to the experimental sets. GAPDH and EF1α had the highest expression stability across different tissues and RPL3 for the other sample set. This study emphasizes the importance of validating superior reference genes for qRT-PCR analysis to accurately normalize gene expression of D. latiflorus Munro.

Selection and validation of reference genes for gene expression analysis in apomictic and sexual Cenchrus ciliaris

Background

Apomixis is a naturally occurring asexual mode of seed reproduction resulting in offspring genetically identical to the maternal plant. Identifying differential gene expression patterns between apomictic and sexual plants is valuable to help deconstruct the trait. Quantitative RT-PCR (qRT-PCR) is a popular method for analyzing gene expression. Normalizing gene expression data using proper reference genes which show stable expression under investigated conditions is critical in qRT-PCR analysis. We used qRT-PCR to validate expression and stability of six potential reference genes (EF1alpha, EIF4A, UBCE, GAPDH, ACT2 and TUBA) in vegetative and reproductive tissues of B-2S and B-12-9 accessions of C. ciliaris.

Findings

Among tissue types evaluated, EF1alpha showed the highest level of expression while TUBA showed the lowest. When all tissue types were evaluated and compared between genotypes, EIF4A was the most stable reference gene. Gene expression stability for specific ovary stages of B-2S and B-12-9 was also determined. Except for TUBA, all other tested reference genes could be used for any stage-specific ovary tissue normalization, irrespective of the mode of reproduction.

Conclusion

Our gene expression stability assay using six reference genes, in sexual and apomictic accessions of C. ciliaris, suggests that EIF4A is the most stable gene across all tissue types analyzed. All other tested reference genes, with the exception of TUBA, could be used for gene expression comparison studies between sexual and apomictic ovaries over multiple developmental stages. This reference gene validation data in C. ciliaris will serve as an important base for future apomixis-related transcriptome data validation.

Expression of auxin-binding protein1 during plum fruit ontogeny supports the potential role of auxin in initiating and enhancing climacteric ripening

Auxin-binding protein1 (ABP1) is an active element involved in auxin signaling and plays critical roles in auxin-mediated plant development. Here, we report the isolation and characterization of a putative sequence from Prunus salicina L., designated PslABP1. The expected protein exhibits a similar molecular structure to that of well-characterized maize-ABP1; however, PslABP1 displays more sequence polarity in the active-binding site due to substitution of some crucial amino-acid residues predicted to be involved in auxin-binding. Further, PslABP1 expression was assessed throughout fruit ontogeny to determine its role in fruit development. Comparing the expression data with the physiological aspects that characterize fruit-development stages indicates that PslABP1 up-regulation is usually associated with the signature events that are triggered in an auxin-dependent manner such as floral induction, fruit initiation, embryogenesis, and cell division and elongation. However, the diversity in PslABP1 expression profile during the ripening process of early and late plum cultivars seems to be due to the variability of endogenous auxin levels among the two cultivars, which consequently can change the levels of autocatalytic ethylene available for the fruit to co-ordinate ripening. The effect of auxin on stimulating ethylene production and in regulating PslABP1 was investigated. Our data suggest that auxin is involved in the transition of the mature green fruit into the ripening phase and in enhancing the ripening process in both auxin- and ethylene-dependent manners thereafter.

Reference gene selection for quantitative real-time PCR in Chrysanthemum subjected to biotic and abiotic stress

Quantitative real-time PCR (RT-qPCR) is a reliable method for assessing gene expression, provided that suitable reference genes are included to normalize the data. The stability of expression of eight potential reference genes, namely, tubulin (alpha-2,4 tubulin), actin, EF1 α (elongation factor 1 α), UBC (ubiquitin C), GAPDH (glyceraldehyde-3-phosphate dehydrogenase), psaA (photosynthesis-related plastid gene representing photosystem I), PP2Acs (catalytic subunit of protein phosphatase 2A), and PGK (phosphoglycerate kinase), was assessed in chrysanthemum plants subjected to aphid infestation, heat stress or waterlogging stress using geNorm software. The widely used reference gene EF1 α performed well for aphid infested plants but poorly for waterlogged ones. The catalytic subunit of protein phosphatase 2A (PP2Acs) was the best performing one during heat and waterlogging stress, but was the worst during aphid infestation. The commonly used reference gene actin was generally the least stable of the set. No single gene was suitable for normalization on its own. The choice of reference gene(s) is an important factor in gene expression studies based on RT-qPCR.

Selection of reference genes for quantitative real-time PCR expression studies of microdissected reproductive tissues in apomictic and sexual Boechera

Background

Apomixis, a natural form of asexual seed production in plants, is considered to have great biotechnological potential for agriculture. It has been hypothesised that de-regulation of the sexual developmental pathway could trigger apomictic reproduction. The genus Boechera represents an interesting model system for understanding apomixis, having both sexual and apomictic genotypes at the diploid level. Quantitative qRT-PCR is the most extensively used method for validating genome-wide gene expression analyses, but in order to obtain reliable results, suitable reference genes are necessary. In this work we have evaluated six potential reference genes isolated from a 454 (FLX) derived cDNA library of Boechera. RNA from live microdissected ovules and anthers at different developmental stages, as well as vegetative tissues of apomictic and sexual Boechera, were used to validate the candidates.

Results

Based on homologies with Arabidopsis, six genes were selected from a 454 cDNA library of Boechera: RPS18 (Ribosomal sub protein 18), Efalpha1 (Elongation factor 1 alpha), ACT 2 (Actin2), UBQ (polyubiquitin), PEX4 (Peroxisomal ubiquitin conjugating enzyme) and At1g09770.1 (Arabidopsis thaliana cell division cycle 5). Total RNA was extracted from 17 different tissues, qRT-PCRs were performed, and raw Ct values were analyzed for primer efficiencies and gene ratios. The geNorm and normFinder applications were used for selecting the most stable genes among all tissues and specific tissue groups (ovule, anthers and vegetative tissues) in both apomictic and sexual plants separately. Our results show that BoechRPS18, BoechEfα1, BoechACT2 and BoechUBQ were the most stable genes. Based on geNorm, the combinations of BoechRPS18 and BoechEfα1 or BoechUBQ and BoechEfα1 were the most stable in the apomictic plant, while BoechRPS18 and BoechACT2 or BoechUBQ and BoechACT2 performed best in the sexual plant. When subgroups of tissue samples were analyzed, different optimal combinations were identified in sexual ovules (BoechUBQ and BoechEfα1), in anthers from both reproductive systems (BoechACT2 and BoechEfα1), in apomictic vegetative tissues (BoechEfα1 and BoechACT2) and sexual vegetative tissues (BoechRPS18 and BoechEfα1). NormFinder ranked BoechACT2 as the most stable in the apomictic plant, while BoechRPS18 was the best in the sexual plant. The subgroups analysis identified the best gene for both apomictic and sexual ovules (BoechRPS18), for anthers from both reproductive system (BoechEfα1) and for apomictic and vegetative tissues (BoechACT2 and BoechRPS18 respectively)

Conclusions

From a total of six tested genes, BoechRPS18, BoechEfα1, BoechACT2 and BoechUBQ showed the best stability values. We furthermore provide detailed information for the accurate normalization of specific tissue gene expression analyses of apomictic and sexual Boechera.

Validation of reference genes for gene expression analysis in chicory (Cichorium intybus) using quantitative real-time PCR

BACKGROUND

Quantitative real-time reverse transcriptase polymerase chain reaction (qRT-PCR) is a sensitive technique for quantifying gene expression levels. One or more appropriate reference genes must be selected to accurately compare mRNA transcripts across different samples and tissues. Thus far, only actin-2 has been used as a reference gene for qRT-PCR in chicory, and a full comparison of several candidate reference genes in chicory has not yet been reported.

RESULTS

Seven candidate reference genes, including nicotinamide adenine dinucleotide dehydrogenase (NADHD), actin (ACT), beta-tubulin (TUB), glyceraldehyde-3-phosphate-dehydrogenase (GADPH), histone H3 (H3), elongation factor 1-alpha (EF) and 18S rRNA (rRNA) were selected to study the expression stability for normalisation of gene expression in chicory. Primer specificity and amplification efficiency were verified for each gene. The expression stability of these genes was analysed across chicory root and leaf tissues using geNorm, NormFinder and BestKeeper software. ACT, EF, and rRNA were the most stable genes as identified by the three different analysis methods. In addition, the use of ACT, EF and GAPDH as reference genes was illustrated by analysing 1-FEHII (FEHII) expression in chicory root and leaf tissues. These analyses revealed the biological variation in FEHII transcript expression among the tissues studied, and between individual plants.

CONCLUSIONS

geNorm, NormFinder, and BestKeeper analyses indicated that ACT, EF and rRNA had the highest expression stability across leaf and root tissues, while GAPDH and NADHD showed relatively low expression stability. The results of this study emphasise the importance of validating reference genes for qRT-PCR analysis in chicory. The use of the most stable reference genes such as ACT and EF allows accurate normalisation of gene expression in chicory leaf and root tissues.

Selection of housekeeping genes for gene expression studies on the development of fruit bearing shoots in Chinese jujube (Ziziphus jujube Mill.)

Chinese jujube (Ziziphus jujube Mill.) is important economically for its fruit and also bears attractive medical value. Its flower development concurs with the growth of current fruit bearing shoots (FBSs). However, events involved in current FBSs, including FBS differentiation, flower development, and reliable housekeeping gene are still unknown. In this study, the morphology of FBS development and floral formation were examined and expression profiles of several potential internal control genes was determined. These included genes encoding proteins involved in protein translation (translation elongation factor 1alpha, ZjEF1), protein folding (cyclophilin, ZjCyP) or degradation (ubiquitin extension protein, ZjUBQ), and proteins involved in the structure of the cytoskeleton (beta-actin, ZjACT) or nucleosome (histone3, ZjH3). Our results showed that the floral development in early growing FBSs (less than 20 mm in length) or shoot apices was not complete. Among ZjACT, ZjEF1, ZjCyP, ZjUBQ, and ZjH3, ZjH3 was the most suitable housekeeping gene to evaluate FBS development, based on their expression in early growing FBSs, shoot apices, and different organs. These results will be useful for further molecular mechanism study about FBS development in Chinese jujube.

Housekeeping gene selection for real-time RT-PCR normalization in potato during biotic and abiotic stress

Plant stress studies are more and more based on gene expression. The analysis of gene expression requires sensitive, precise, and reproducible measurements for specific mRNA sequences. Real-time RT-PCR is at present the most sensitive method for the detection of low abundance mRNA. To avoid bias, real-time RT-PCR is referred to one or several internal control genes, which should not fluctuate during treatments. Here, the non-regulation of seven housekeeping genes (beta-tubulin, cyclophilin, actin, elongation factor 1-alpha (ef1alpha), 18S rRNA, adenine phosphoribosyl transferase (aprt), and cytoplasmic ribosomal protein L2) during biotic (late blight) and abiotic stresses (cold and salt stress) was tested on potato plants using geNorm software. Results from the three experimental conditions indicated that ef1alpha was the most stable among the seven tested. The expression of the other housekeeping genes tested varied upon stress. In parallel, a study of the variability of expression of hsp20.2, shown to be implicated in late blight stress, was realized. The relative quantification of the hsp20.2 gene varied according to the internal control and the number of internal controls used, thus highlighting the importance of the choice of internal controls in such experiments.

Alteration of the embryo transcriptome of hexaploid winter wheat (Triticum aestivum cv. Mercia) during maturation and germination

Grain dormancy and germination are areas of biology that are of considerable interest to the cereal community. We have used a 9,155-feature wheat unigene cDNA microarray resource to investigate changes in the wheat embryo transcriptome during late grain development and maturation and during the first 48 h of postimbibition germination. In the embryo 392 mRNAs accumulated by twofold or greater over the time course from 21 days postanthesis (dpa) to 40 dpa and on through 1 and 2 days postgermination. These included mRNAs encoding proteins involved in amino acid biosynthesis and metabolism, cell division and subsequent cell development, signal transduction, lipid metabolism, energy production, protein turnover, respiration, initiation of transcription, initiation of translation and ribosomal composition. A number of mRNAs encoding proteins of unknown function also accumulated over the time course. Conversely 163 sequences showed decreases of twofold or greater over the time course. A small number of mRNAs also showed rapid accumulation specifically during the first 48 h of germination. We also examined alterations in the accumulation of transcripts encoding proteins involved in abscisic acid signalling. Thus, we describe changes in the level of transcripts encoding wheat Viviparous 1 (Vp1) and other interacting proteins. Interestingly, the transcript encoding wheat Viviparous-interacting protein 1 showed a pattern of accumulation that correlates inversely with germination. Our data suggests that the majority of the transcripts required for germination accumulate in the embryo prior to germination and we discuss the implications of these findings with regard to manipulation of germination in wheat.

Real-time PCR: what relevance to plant studies?

The appearance of genetically modified organisms on the food market a few years ago, and the demand for more precise and reliable techniques to detect foreign (transgenic or pathogenic) DNA in edible plants, have been the driving force for the introduction of real-time PCR techniques in plant research. This was followed by numerous fundamental research applications aiming to study the expression profiles of endogenous genes and multigene families. Since then, the interest in this technique in the plant scientist community has increased exponentially. This review describes the technical features of quantitative real-time PCR that are especially relevant to plant research, and summarizes its present and future applications.