Comparative physiology and transcriptome response patterns in cold-tolerant and cold-sensitive varieties of Solanum melongena

BACKGROUND

Climate change has led to severe cold events, adversely impacting global crop production. Eggplant (Solanum melongena L.), a significant economic crop, is highly susceptible to cold damage, affecting both yield and quality. Unraveling the molecular mechanisms governing cold resistance, including the identification of key genes and comprehensive transcriptional regulatory pathways, is crucial for developing new varieties with enhanced tolerance.

RESULTS

In this study, we conducted a comparative analysis of leaf physiological indices and transcriptome sequencing results. The orthogonal partial least squares discriminant analysis (OPLS-DA) highlighted peroxidase (POD) activity and soluble protein as crucial physiological indicators for both varieties. RNA-seq data analysis revealed that a total of 7024 and 6209 differentially expressed genes (DEGs) were identified from variety "A" and variety "B", respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment of DEGs demonstrated that the significant roles of starch and sucrose metabolism, glutathione metabolism, terpenoid synthesis, and energy metabolism (sucrose and starch metabolism) were the key pathways in eggplant. Weighted gene co-expression network analysis (WGCNA) shown that the enrichment of numerous cold-responsive genes, pathways, and soluble proteins in the MEgrep60 modules. Core hub genes identified in the co-expression network included POD, membrane transporter-related gene MDR1, abscisic acid-related genes, growth factor enrichment gene DELLA, core components of the biological clock PRR7, and five transcription factors. Among these, the core transcription factor MYB demonstrated co-expression with signal transduction, plant hormone, biosynthesis, and metabolism-related genes, suggesting a pivotal role in the cold response network.

CONCLUSION

This study integrates physiological indicators and transcriptomics to unveil the molecular mechanisms responsible for the differences in cold tolerance between the eggplant cold-tolerant variety "A" and the cold-sensitive variety "B". These mechanisms include modulation of reactive oxygen species (ROS), elevation in osmotic carbohydrate and free proline content, and the expression of terpenoid synthesis genes. This comprehensive understanding contributes valuable insights into the molecular underpinnings of cold stress tolerance, ultimately aiding in the improvement of crop cold tolerance.

Overexpression of a BR inactivating enzyme gene GhPAG1 impacts eggplant fruit development and anthocyanin accumulation mainly by altering hormone homeostasis

Brassinosteroids (BRs) function importantly in plant growth and development, but the roles in regulating fruit development and anthocyanin pigmentation remain unclear. Eggplant (Solanum melongena L.) is an important Solanaceae vegetable crop rich in anthocyanins. The fruit size and coloration are important agronomic traits for eggplant breeding. In this study, transgenic eggplant exhibiting endogenous BRs deficiency was created by overexpressing a heterologous BRs-inactivating enzyme gene GhPAG1 driven by CaMV 35 S promoter. 35 S::GhPAG1 eggplant exhibited severe dwarfism, reduced fruit size, and less anthocyanin accumulation. Microscopic observation showed that the cell size of 35 S::GhPAG1 eggplant was significantly reduced compared to WT. Furthermore, the levels of IAA, ME-IAA, and active JAs (JA, JA-ILE, and H2JA) all decreased in 35 S::GhPAG1 eggplant fruit. RNA-Seq analyses showed a decrease in the expression of genes involved in cell elongation, auxin signaling, and JA signaling. Besides, overexpression of GhPAG1 significantly downregulated anthocyanin biosynthetic genes and associated transcription regulators. Altogether, these results strongly suggest that endogenous brassinosteroid deficiency arising from GhPAG1 overexpression impacts eggplant fruit development and anthocyanin coloration mainly by altering hormone homeostasis.

The MYB transcription factor SmMYB113 directly regulates ethylene-dependent flower abscission in eggplant

Flower abscission is an important developmental process that can significantly reduce the yield of horticultural plants. We previously reported that SmMYB113 is a key transcription factor promoting anthocyanin biosynthesis and improve fruit quality. However, the overexpression of SmMYB113 in eggplant increased flower drop rate and reduced fruit yield. Here, we elucidate the regulatory mechanisms of SmMYB113 on flower abscission in eggplant. RNA-seq analysis indicated that the regulation of flower abscission by SmMYB113 was associated with altered expression of genes related to ethylene biosynthesis and signal transduction, including ethylene biosynthetic genes SmACS1, SmACS8 and SmACO4. Then, the ethylene content in flowers and the function of ethephon (ETH, which promotes fruit ripening) and 1-Methylcyclopropene (1-MCP, which acts as an ethylene perception inhibitor) were analyzed, which revealed that SmMYB113 directly regulates ethylene-dependent flower abscission. Yeast one-hybrid and dual-luciferase assays revealed that SmMYB113 could directly bind to the promoters of SmACS1, SmACS8, and SmACO4 to activate their expression. Through construction of a yeast two-hybrid (Y2H) screening library, the protein SmERF38 was found to interact with SmMYB113, and verified by Y2H, bimolecular fluorescence complementation (BiFC), and luciferase complementation assay. Furthermore, dual-luciferase assays showed that SmERF38 enhanced the role of SmMYB113 on the promoters of SmACS1. Our results provided new insight into the molecular mechanism of flower abscission in eggplant.

Decreased cadmium content in Solanum melongena induced by grafting was related to glucosinolates synthesis

Grafting is an effective horticultural method to reduce Cd accumulation in crops. However, the mechanism of grafting inducing the decrease in Cd content in scions remains unclear. This study evaluated the effect of grafting on fruit quality, yield, and Cd content of Solanum melongena, and explored the potential mechanism of grafting reducing Cd content in scions. In the low Cd-contaminated soil, compared with un-grafted (UG) and self-grafted plants (SG), the fruit yield of inter-grafted plants (EG) increased by 38 %, and the fruit quality was not markedly affected. In EG, the decrease in total S and Cd content was not related to organic acids and thiol compounds. The decrease in total S and Cd content in EG leaves and fruits was closely related to the synthesis and transportation of glucosinolates (GSL). The genes encoding GSL synthesis in leaves, such as basic helix-loop-helix, myelocytomatosis proteins, acetyl-CoA, cytochrome P450, and glutathione S-transferases, were significantly downregulated. In EG leaves, the contents of five of the eight amino acids involved in GSL synthesis decreased significantly (P < 0.05). Notably, total GSL in EG stems, leaves, and fruits had a significant linear correlation with total S and Cd. In summary, the decrease in total S and Cd content in scions caused by grafting is closely related to GSL. Our findings provide a theoretical basis for the safe use of Cd-contaminated soil, exploring the long-distance transport of Cd in plants and cultivating crops with low Cd accumulation.

Effect of salinity on growth and biochemical responses of brinjal varieties: implications for salt tolerance and antioxidant mechanisms

Salinity poses significant challenges to agricultural productivity, impacting crops' growth, morphology and biochemical parameters. A pot experiment of three months was conducted between February to April 2023 in the Department of Botany, The Islamia University of Bahawalpur. Four brinjal (eggplant) varieties: ICS-BR-1351, HBR-313-D, HBR-314-E, and HBR-334-D were selected and assessed for the effects of salinity on various growth and biochemical attributes. The experiment was completely randomized in design with three replicates each. This study revealed that increased salinity significantly reduced the shoot length, root length, and leaf number across all varieties, with maximum adverse effects observed at a 300mM NaCl concentration. Among the tested varieties, ICS-BR-1351 demonstrated superior performance in most growth parameters, suggesting potential salt tolerance. Biochemically, salinity decreased chlorophyll content across all varieties, with the sharpest decline observed at the highest salt concentration. V4 (HBR-334-D) showed a 57% decrease in chlorophyll followed by V3 (HBR-314-E) at 56%, V2 (HBR-313-D) at 54%, and V1 (ICS-BR-1351) at 33% decrease at maximum salt levels as compared to control. Conversely, carotenoid content increased up to -42.11% in V3 followed by V2 at -81.48%, V4 at -94.11%, and - 233% in V1 at 300mM NaCl stress as compared to respective controls. V3 (HBR-314-E) has the maximum value for carotenoids while V1 has the lowest value for carotenoids as compared to the other three brinjal varieties. In addition to pigments, the study indicated a salinity-induced decrease in total proteins and total soluble sugar, whereas total amino acids and flavonoids increased. Total proteins showed a decrease in V2 (49.46%) followed by V3 (36.44%), V4 (53.42%), and V1 (53.79%) at maximum salt concentration as compared to plants treated with tap water only. Whereas, total soluble sugars showed a decrease of 52.07% in V3, 41.53% in V2, 19.49% in V1, and 18.99% in V4 at the highest salt level. While discussing total amino acid, plants showed a -9.64% increase in V1 as compared to V4 (-31.10%), V2 (-36.62%), and V3 (-22.61%) with high salt levels in comparison with controls. Plant flavonoid content increased in V3 (-15.61%), V2 (-19.03%), V4 (-18.27%) and V1 (-27.85%) at 300mM salt concentration. Notably, salinity elevated the content of anthocyanin, lycopene, malondialdehyde (MDA), and hydrogen peroxide (H2O2) across all varieties. Antioxidant enzymes like peroxidase, catalase, and superoxide dismutase also increased under salt stress, suggesting an adaptive response to combat oxidative damage. However, V3 (HBR-314-E) has shown an increase in anthocyanin at -80.00%, lycopene at -24.81%, MDA at -168.04%, hydrogen peroxide at -24.22%, POD at -10.71%, CAT as-36.63 and SOD as -99.14% at 300mM NaCl stress as compared to control and other varieties. The enhanced accumulation of antioxidants and other protective compounds suggests an adaptive mechanism in brinjal to combat salt-induced oxidative stress. The salt tolerance of different brinjal varieties was assessed by principal component analysis (PCA), and the order of salt tolerance was V1 (ICS-BR-1351) > V4 (HBR-334-D), > V2 (HBR-313-D) > V3 (HBR-314-E). Among the varieties studied, ICS-BR-1351 demonstrated resilience against saline conditions, potentially offering a promising candidate for saline-prone agricultural areas.

Identification and Molecular Characterization of the CAMTA Gene Family in Solanaceae with a Focus on the Expression Analysis of Eggplant Genes under Cold Stress

Calmodulin-binding transcription activator (CAMTA) is an important calmodulin-binding protein with a conserved structure in eukaryotes which is widely involved in plant stress response, growth and development, hormone signal transduction, and other biological processes. Although CAMTA genes have been identified and characterized in many plant species, a systematic and comprehensive analysis of CAMTA genes in the Solanaceae genome is performed for the first time in this study. A total of 28 CAMTA genes were identified using bioinformatics tools, and the biochemical/physicochemical properties of these proteins were investigated. CAMTA genes were categorized into three major groups according to phylogenetic analysis. Tissue-expression profiles indicated divergent spatiotemporal expression patterns of SmCAMTAs. Furthermore, transcriptome analysis of SmCAMTA genes showed that exposure to cold induced differential expression of many eggplant CAMTA genes. Yeast two-hybrid and bimolecular fluorescent complementary assays suggested an interaction between SmCAMTA2 and SmERF1, promoting the transcription of the cold key factor SmCBF2, which may be an important mechanism for plant cold resistance. In summary, our results provide essential information for further functional research on Solanaceae family genes, and possibly other plant families, in the determination of the development of plants.

Solanum melongena extract supplementation protected skeletal muscle and brain damage by regulation of BDNF/PGC1α/irisin pathway via brain function-related myokines in high-fat diet induced obese mice

In this study, we investigated the protective effects of SM on skeletal muscle and brain damage by regulation of BDNF/PGC1α/irisin pathway via brain function related myokines in high-fat diet-induced OB mice. OB was induced by high-fat diet for 6 weeks. SM extract (SME) was administered with 200 mg/kg BW (LSM) and 500 mg/kg BW (HSM) by oral gavage every day for 12 weeks. Behavior tests such as grip strength, Y-maze, and passive avoidance test were conducted to analyze muscle and cognitive function. Histopathological changes in skeletal muscle and brain were examined by hematoxylin and eosin staining and the protein levels of biomarkers related to oxidative stress, inflammation, protein degradation, neuro-plasticity, and cell cycling were measured by western blot. SME regulated morphological changes (muscle cross-sectional area: 1.23%, 1.40%; density of neurons in hippocampus:1.74%, 1.73%) in T2DM mice. Importantly, SME supplementation significantly increased several muscle-derived myokines which might influence the expression of neuronal markers in OB mice (FGF21: 1.27%, 1.34%; PGC1α: 1.0%, 1.32%; IRISIN: 1.9%, 1.08%; BDNF: 1.35%, 1.23%). Accordingly, SME activated hippocampal neurotrophic factors including BDNF (1.0%, 1.2%) and its associated PGC1α/irisin pathway (PGC1α :1.1%, 1.1%; IRISIN:1.1%, 0.9%) significantly. This study demonstrated the possibliy that protective myokines increased by SME supplementation may contribute to neuro-protection in OB mice. Taken together, the current study suggests that SME can be used to prevent skeletal muscle and brain damage in OB by protecting against oxidative stress and inflammatin via modulation of the BDNF/PGC1α/irisin pathway in the therapeutic approach of obese patients.

Eggplant transcription factor SmMYB5 integrates jasmonate and light signaling during anthocyanin biosynthesis

Low light conditions severely suppress anthocyanin synthesis in fruit skins, leading to compromised fruit quality in eggplant (Solanum melongena L.) production. In this study, we found that exogenous methyl-jasmonate (MeJA) application can effectively rescue the poor coloration of the eggplant pericarp under low light conditions. However, the regulatory relationship between jasmonate and light signaling for regulating anthocyanin synthesis remains unclear. Here, we identified a JA response factor, SmMYB5, as an anthocyanin positive regulator by applying RNA-sequencing and characterization of transgenic plants. Firstly, we resolved that SmMYB5 can interact with TRANSPARENT TESTA8 (SmTT8), an anthocyanin-promoted BASIC HELIX-LOOP-HELIX (bHLH) transcription factor, to form the SmMYB5-SmTT8 complex and activate CHALCONE SYNTHASE (SmCHS), FLAVANONE-3-HYDROXYLASE (SmF3H), and ANTHOCYANIN SYNTHASE (SmANS) promoters by direct binding. Secondly, we revealed that JA signaling repressors JASMONATE ZIM DOMAIN5 (SmJAZ5) and SmJAZ10 can interfere with the stability and transcriptional activity of SmMYB5-SmTT8 by interacting with SmMYB5. JA can partially rescue the transcriptional activation of SmF3H and SmANS promoters by inducing SmJAZ5/10 degradation. Thirdly, we demonstrated that the protein abundance of SmMYB5 is regulated by light. CONSTITUTIVELY PHOTOMORPHOGENIC1 (SmCOP1) interacts with SmMYB5 to trigger SmMYB5 degradation via the 26S proteasome pathway. Finally, we delineated a light-dependent JA-SmMYB5 signaling pathway that promotes anthocyanin synthesis in eggplant fruit skins. These results provide insights into the mechanism of the integration of JA and light signals in regulating secondary metabolite synthesis in plants.

SmWRKY11 acts as a positive regulator in eggplant response to salt stress

Salt stress is one of the most threatening abiotic stresses to plants, which can seriously affect plant growth, development, reproduction, and yield. However, the mechanisms of plant against salt stress largely remain unclear. Herein, SmWRKY11, an assumed WRKY transcription factor, was functionally characterized in eggplant against salt stress. SmWRKY11 was significantly up-regulated by salt, dehydration stress, and ABA treatment. SmWRKY11 located in the nucleus, and the Plant_zn_clust conserved domain exhibited transcriptional activation activity. Silencing of SmWRKY11 enhanced the susceptibility of eggplant to salt stress, accompanied by significantly down-regulation of transcript expression levels of salt stress defense-related genes SmNCED1, SmGSTU10, and positive regulator of salt stress response SmERF1 as well as increase of hydrogen peroxide (H2O2) content and decrease of the enzyme activities of catalase (CAT), peroxidase (POD), and ascorbate peroxidase (APX). In addition, silencing of SmERF1 also could significantly down-regulate SmWRKY11 expression in eggplant response to salt stress. By luciferase reporter assay and chromatin immunoprecipitation PCR assay, SmERF1 expression was found to be indirectly activated by SmWRKY11. These data indicate that SmWRKY11 acts as a positive regulator by forming positive feedback loop with SmERF1 via an indirect regulatory manner in eggplant response to salt stress.

Genome-Wide Identification of Catalase Gene Family and the Function of SmCAT4 in Eggplant Response to Salt Stress

Salinity is an important abiotic stress, damaging plant tissues by causing a burst of reactive oxygen species (ROS). Catalase (CAT) enzyme coded by Catalase (CAT) genes are potent in reducing harmful ROS and hydrogen peroxide (H2O2) produced. Herein, we performed bioinformatics and functional characterization of four SmCAT genes, retrieved from the eggplant genome database. Evolutionary analysis CAT genes revealed that they are divided into subgroups I and II. The RT-qPCR analysis of SmCAT displayed a differential expression pattern in response to abiotic stresses. All the CAT proteins of eggplant were localized in the peroxisome, except for SmCAT4, which localized in the cytomembrane and nucleus. Silencing of SmCAT4 compromised the tolerance of eggplant to salt stress. Suppressed expression levels of salt stress defense related genes SmTAS14 and SmDHN1, as well as increase of H2O2 content and decrease of CAT enzyme activity was observed in the SmCAT4 silenced eggplants. Our data provided insightful knowledge of CAT gene family in eggplant. Positive regulation of eggplant response to salinity by SmCAT4 provides resource for future breeding programs.

Single-cell RNA sequencing identifies eggplant as a regulator of germ cell development in Drosophila

Drosophila ovarian germline stem cells (GSCs) are a powerful model for stem cell research. In this study, we use single-cell RNA sequencing (scRNA-seq), an RNAi screen and bioinformatic analysis, to identify genes involved in germ cell differentiation, including 34 genes with upregulated expression during early germ cell development and 19 genes that may regulate germ cell differentiation. Among these, a gene we have named eggplant (eggpl) is highly expressed in GSCs and downregulated in early daughter cells. RNAi knockdown of eggpl causes germ cell proliferation and differentiation defects. In flies fed a rich yeast diet, the expression of eggpl is significantly lower and knockdown or knockout of eggpl phenocopies a rich diet. In addition, eggpl knockdown suppresses the reduction in germ cell proliferation caused by inhibition of the insulin effector PI3K. These findings suggest that downregulation of eggpl links nutritional status to germ cell proliferation and differentiation. Collectively, this study provides new insights into the signaling networks that regulate early germ cell development and identifies eggpl as a key player in this process.

Improving the isolated microspore culture in eggplant (Solanum melongena L.) with amino acid nutrition

It has been proposed that the composition of the culture medium, especially its amino acids, is an important part of getting microspore androgenesis to occur in some plants. However, there have been far fewer studies done on the Solanaceae family. In this study, we studied what happened to eggplant microspore culture when we mixed casein hydrolysate (0 and 100 mg L-1) with four amino acids: proline (0, 100, 500, and 900 mg L-1), glutamine (0 and 800 mg L-1), serine (0 and 100 mg L-1), and alanine (0 and 100 mg L-1). The results showed that a combination of 800 mg L-1 of glutamine, 100 mg L-1 of serine, 100 mg L-1 of casein hydrolysate, and 500 mg L-1 of proline produced the maximum number of calli per Petri dish (938). Calli had a globular shape and a compact appearance when formed in media containing 500 mg L-1 of proline (alone or combined with serine, alanine, and/or casein hydrolysate). Most of these structures were observed in a medium with 500 mg L-1 of proline, 100 mg L-1 of casein hydrolysate, and 100 mg L-1 of serine. We also investigated what happened when gum arabic (2400, 2600, 3600, 4600, and 5600 mg L-1) was combined with proline (0 and 500 mg L-1), casein hydrolysate (0 and 100 mg L-1), and glutamine (0, 400, and 800 mg L-1). The findings demonstrated the involvement of proline in the increase of calli. Overall, the results give us new information about how amino acids work in eggplant microspore culture and suggest that proline can move this plant's microspore androgenesis pathway forward.

Transcriptomics reveals the molecular mechanisms of flesh colour differences in eggplant (Solanum melongena)

BACKGROUND

Fruit flesh colour is not only an important commodity attribute of eggplant but is also closely related to maturity. However, very little is known about its formation mechanism in eggplant.

RESULTS

Two inbred lines of eggplant, green 'NC7' and white 'BL', were used in this study to explain the differences in flesh colour. Transcriptome sequencing results revealed a total of 3304 differentially expressed genes (DEGs) in NC7 vs. BL. Of the DEGs obtained, 2050 were higher and 1254 were lower in BL. These DEGs were annotated to 126 pathways, where porphyrin and chlorophyll metabolism, flavonoid biosynthesis, and photosynthesis-antenna proteins play vital roles in the colour formation of eggplant flesh. At the same time, Gene Ontology (GO) enrichment significance analysis showed that a large number of unigenes involved in the formation of chloroplast structure were lower in BL, which indicated that the formation of chloroplasts in white-fleshed eggplant was blocked. This was confirmed by transmission electron microscopy (TEM), which found only leucoplasts but no chloroplasts in the flesh cells of white-fleshed eggplant. Several genes encoding ERF and bHLH transcription factors were predicted to participate in the regulation of chlorophyll biosynthetic genes.

CONCLUSIONS

The results of this study indicated that differences in the gene expression of the chlorophyll metabolic pathway were the main cause of the different flesh colour formations. These findings will increase our understanding of the genetic basis in eggplant flesh colors formation mechanism.

Genome-Wide Analysis and Characterization of Eggplant F-Box Gene Superfamily: Gene Evolution and Expression Analysis under Stress

F-box genes play an important role in plant growth and resistance to abiotic and biotic stresses. To date, systematic analysis of F-box genes and functional annotation in eggplant (Solanum melongena) is still limited. Here, we identified 389 F-box candidate genes in eggplant. The domain study of F-box candidate genes showed that the F-box domain is conserved, whereas the C-terminal domain is diverse. There are 376 SmFBX candidate genes distributed on 12 chromosomes. A collinearity analysis within the eggplant genome suggested that tandem duplication is the dominant form of F-box gene replication in eggplant. The collinearity analysis between eggplant and the three other species (Arabidopsis thaliana, rice and tomato) provides insight into the evolutionary characteristics of F-box candidate genes. In addition, we analyzed the expression of SmFBX candidate genes in different tissues under high temperature and bacterial wilt stress. The results identified several F-box candidate genes that potentially participate in eggplant heat tolerance and bacterial wilt resistance. Moreover, the yeast two-hybrid assay showed that several representative F-box candidate proteins interacted with representative Skp1 proteins. Overexpression of SmFBX131 and SmFBX230 in tobacco increased resistance to bacterial wilt. Overall, these results provide critical insights into the functional analysis of the F-box gene superfamily in eggplant and provide potentially valuable targets for heat and bacterial resistance.

Metabolomic and transcriptomic analyses identify quinic acid protecting eggplant from damage caused by western flower thrips

BACKGROUND

Western flower thrips are considered the major insect pest of horticultural crops worldwide, causing economic and yield loss to Solanaceae crops. The eggplant (Solanum melongena L.) resistance against thrips remains largely unexplored. This work aims to identify thrips-resistant eggplants and dissect the molecular mechanisms underlying this resistance using the integrated metabolomic and transcriptomic analyses of thrips-resistant and -susceptible cultivars.

RESULTS

We developed a micro-cage thrips bioassay to identify thrips-resistant eggplant cultivars, and highly resistant cultivars were identified from wild eggplant relatives. Metabolomic profiles of thrips-resistant and -susceptible eggplant were compared using the gas chromatography-mass spectrometry (GC-MS)-based approach, resulting in the identification of a higher amount of quinic acid in thrips-resistant eggplant compared to the thrips-susceptible plant. RNA-sequencing analysis identified differentially expressed genes (DEGs) by comparing genome-wide gene expression changes between thrips-resistant and -susceptible eggplants. Consistent with metabolomic analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of DEGs revealed that the starch and sucrose metabolic pathway in which quinic acid is a metabolic by-product was highly enriched. External application of quinic acid enhances the resistance of susceptible eggplant to thrips.

CONCLUSION

Our results showed that quinic acid plays a key role in the resistance to thrips. These findings highlight a potential application of quinic acid as a biocontrol agent to manage thrips and expand our knowledge to breed thrips-resistant eggplant. © 2022 Society of Chemical Industry.

Integrated Metabolome and Transcriptome Analysis Reveals a Regulatory Network of Fruit Peel Pigmentation in Eggplant (Solanum melongena L.)

The color of fruit peel is an economically important character of eggplant, and black-purple eggplant has received much attention for being rich in anthocyanin. However, the reason why different fruit peel colors form in eggplant is not well understood. In the present study, an integrative analysis of the metabolome and transcriptome profiles was performed in five eggplant varieties with different fruit colors. A total of 260 flavonoids were identified, and most of them showed significantly higher abundance in black-purple varieties than in other varieties. The transcriptome analysis indicated the activation of early phenylpropanoid biosynthesis genes (SmPAL, SmC4H, and Sm4CL) was more responsible for anthocyanin accumulation, while SmF3′5′H was the key factor for the formation of a purple color. Furthermore, two transcription factors, SmGL2 and SmGATA26, were identified as new hub genes associated with anthocyanin accumulation. The silencing of SmGL2 and SmGATA26 reduced anthocyanin accumulation in eggplant fruit peels, suggesting the possible involvement of SmGL2 and SmGATA26 in regulating anthocyanin biosynthesis. In addition, the pathway of plant hormone signal transduction was significantly enriched, indicating that phytohormones may cooperatively interact to modulate flavonoid biosynthesis. This study provides comprehensive information of flavonoid metabolites and new insights into the regulatory network of fruit coloration, which might be useful for the molecular breeding of eggplant.

AMF and PSB applications modulated the biochemical and mineral content of the eggplants

This study was conducted to investigate the beneficial role of phosphate solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) in improving eggplant fruits' biochemical composition and mineral content. The plants were treated with AMF Acaulospora laevis, and bacteria Pseudomonas fluorescens, and the corresponding variations were measured for mineral content (Ca, Fe, Mg, K, and P), biochemical parameters (dry matter, total soluble solid [TSS], phenolics, chlorogenic acid, vitamin C) along with arbuscular mycorrhiza spore number, and percentage of root colonization. The AMF and PSB-mediated soil and root-associated nutrients become available for uptake via mineralization, solubilization, and mobilization, primarily through the generation of organic acids and P-hydrolysing enzymes by the microbes. All the treatments showed a significant increase in the concentrations of different biochemical components. However, the combination of both A. laevis and P. fluorescens was found to be the most efficient. These results indicated the possibility of A. laevis and P. fluorescens being used as biofertilizers.

Construction of a High-Density Recombination Bin-Based Genetic Map Facilitates High-Resolution Mapping of a Major QTL Underlying Anthocyanin Pigmentation in Eggplant

High-density genetic maps can significantly improve the resolution of QTL mapping. We constructed a high-density recombination bin-based genetic map of eggplant based on 200 F₂ plants from an interspecific cross (Solanum melongena × S. incanum) using the whole genome resequencing strategy. The map was 2022.8 cM long, covering near 99% of the eggplant genome. The map contained 3776 bins, with 3644 (96.5%) being effective (position non-redundant) ones, giving a nominal average distance of 0.54 cM and an effective average distance of 0.56 cM between adjacent bins, respectively. Using this map and 172 F_2:3 lines, a major QTL with pleiotropic effects on two anthocyanin pigmentation-related traits, leaf vein color (LVC) and fruit pericarp color (FPC), was steadily detected in a bin interval of 2.28 cM (or 1.68 Mb) on chromosome E10 in two cropping seasons, explaining ~65% and 55% of the phenotypic variation in LVC and FPC, respectively. Genome-wide association analysis in this population validated the QTL and demonstrated the correctness of mapping two bins of chromosome E02 onto E10. Bioinformatics analysis suggested that a WDR protein gene inside the bin interval with reliable effective variation between the two parents could be a possible candidate gene of the QTL.

[Genome-wide identification and analysis of the TCP gene family in eggplant (Solanum melongena L.)]

TCP (teosinte branched1/cincinnata/proliferating cell factor) is a group of plant-specific transcription factors that play important roles in plant growth and development. To date, there are no report about TCP transcription factors in eggplant (Solanum melongena L). In this study, twenty-nine eggplant TCP (SmTCP) family genes distributed on 11 chromosomes were identified from the genome database of eggplant using bioinformatics methods. The results showed that all members of the family contained sequences encoding TCP conserved domains with length of amino acids ranging from 201 to 538 and exon numbers of 1 or 2. Subcellular localization revealed that three SmTCP proteins (SmTCP02/03/21) were located in the cytoplasm and the other SmTCP proteins were located in the nucleus. The 29 TCP transcription factors were divided into ClassⅠ (PCF) and ClassⅡ (CIN and CYC/TB1) by phylogenetic tree and sequence analysis. Collinearity analysis showed that 17 pairs (21) of SmTCP genes had collinearity, and these collinearity genes belonged to segmental duplication. Analysis of gene expression patterns showed that all 29 members of SmTCP gene family were expressed in 15 tissues or organs, but the expression patterns were different. Among them, four gene (SmTCP18/19/20/25) of CIN subfamily were highly expressed in leaves at different growth stages. Analysis of cis-acting elements in the promoter region of SmTCP showed that there were four types of cis-acting elements, which were light response related cis-acting elements, growth and development related cis-acting elements, hormone response related cis-acting elements and stress related cis-acting elements. In summary, the molecular basis of SmTCP genes in eggplant and the influence of TCP gene on the growth and development of eggplant provided a theoretical basis for molecular breeding of eggplant.

Fine mapping and characterization of the dominant gene SmFTSH10 conferring non-photosensitivity in eggplant (Solanum melongena L.)

A candidate non photosensitive gene S m F TS H10 was identified by combining bulked segregant analysis and map‑based cloning. Low light condition often leads to poor coloration of photosensitive eggplant. Here, we obtained a non-photosensitive eggplant that can synthesize large amount of anthocyanin under shading conditions. Genetic analysis of F₁ and F₂ populations revealed that the phenotype of non-photosensitivity was regulated by a single dominant nuclear gene, herein temporarily designated SmFTSH10. Through Bulked segregant analysis (BSA), SNP haplotyping and fine genetic mapping delimited SmFTSH10 to a 290 kb region of eggplant chromosome 10 flanking by markers dCAPS21 and dCAPS32. Sequence analysis revealed C-base deletion in the fourth exon of SmFTSH10 resulted in premature termination of translation. The expression level of SmFTSH10 decreased significantly in anthocyanin-rich parts of mutant '145' compared with the wild-type 'LSHX'. Sequencing of 10 recombinants revealed that the C-base deletion in the 4th exon of SmFTSH10 was co-segregated with the non-photosensitive phenotype, and the sequencing analysis of the natural population of eggplant also showed that the Indel in SmFTSH10 had a high accuracy in the identification of the photosensitivity of eggplant. Light-responsive expression patterns analysis suggests that it has the same expression trend as the genes involved in eggplant anthocyanin biosynthesis, which supports SmFTSH10 as the most possible candidate gene of non-photosensitivity. These findings provide a new insight into understanding the molecular mechanisms of anthocyanin biosynthesis in non-photosensitive eggplant.

Weighted Gene Co-Expression Analysis Network-Based Analysis on the Candidate Pathways and Hub Genes in Eggplant Bacterial Wilt-Resistance: A Plant Research Study

Solanum melongena L. (eggplant) bacterial wilt is a severe soil borne disease. Here, this study aimed to explore the regulation mechanism of eggplant bacterial wilt-resistance by transcriptomics with weighted gene co-expression analysis network (WGCNA). The different expression genes (DEGs) of roots and stems were divided into 21 modules. The module of interest (root: indianred4, stem: coral3) with the highest correlation with the target traits was selected to elucidate resistance genes and pathways. The selected module of roots and stems co-enriched the pathways of MAPK signalling pathway, plant pathogen interaction, and glutathione metabolism. Each top 30 hub genes of the roots and stems co-enriched a large number of receptor kinase genes. A total of 14 interesting resistance-related genes were selected and verified with quantitative polymerase chain reaction (qPCR). The qPCR results were consistent with those of WGCNA. The hub gene of EGP00814 (namely SmRPP13L4) was further functionally verified; SmRPP13L4 positively regulated the resistance of eggplant to bacterial wilt by qPCR and virus-induced gene silencing (VIGS). Our study provides a reference for the interaction between eggplants and bacterial wilt and the breeding of broad-spectrum and specific eggplant varieties that are bacterial wilt-resistant.

A light-responsive transcription factor SmMYB35 enhances anthocyanin biosynthesis in eggplant (Solanum melongena L.)

SmMYB35, a light-responsive R2R3-MYB transcription factor, positively regulates anthocyanin biosynthesis in eggplant by binding to the promoters of SmCHS, SmF3H, SmDFR, and SmANS and enhancing their activities. In addition, SmMYB35 interacts with SmTT8 and SmTTG1 to form a MBW complex, thereby enhancing anthocyanin biosynthesis. Eggplant is a vegetable rich in anthocyanins. SmMYB35, a light-responsive R2R3-MYB transcription factor, was isolated from eggplant and investigated for its biological functions. The results suggested that the expression of SmMYB35 was regulated by SmHY5 through directly binding to G-box in the promoter region, and the overexpression of SmMYB35 could increase the anthocyanin content in the stems and petals of the transgenic eggplants. SmMYB35 could also bind to the promoters of SmCHS, SmF3H, SmDFR, and SmANS and enhance their activities. In addition, SmMYB35 interacted with SmTT8 and SmTTG1 to form a MBW complex which enhanced anthocyanin biosynthesis. Taking together, we firstly verified that SmMYB35 promoted anthocyanin biosynthesis in plants. The results provide new insights into the regulatory effects of SmMYB35 on key anthocyanin biosynthetic genes and advance our understanding of the molecular mechanism of light-induced anthocyanin synthesis in eggplants.

A light-responsive transcription factor SmMYB35 enhances anthocyanin biosynthesis in eggplant (Solanum melongena L.)

SmMYB35, a light-responsive R2R3-MYB transcription factor, positively regulates anthocyanin biosynthesis in eggplant by binding to the promoters of SmCHS, SmF3H, SmDFR, and SmANS and enhancing their activities. In addition, SmMYB35 interacts with SmTT8 and SmTTG1 to form a MBW complex, thereby enhancing anthocyanin biosynthesis. Eggplant is a vegetable rich in anthocyanins. SmMYB35, a light-responsive R2R3-MYB transcription factor, was isolated from eggplant and investigated for its biological functions. The results suggested that the expression of SmMYB35 was regulated by SmHY5 through directly binding to G-box in the promoter region, and the overexpression of SmMYB35 could increase the anthocyanin content in the stems and petals of the transgenic eggplants. SmMYB35 could also bind to the promoters of SmCHS, SmF3H, SmDFR, and SmANS and enhance their activities. In addition, SmMYB35 interacted with SmTT8 and SmTTG1 to form a MBW complex which enhanced anthocyanin biosynthesis. Taking together, we firstly verified that SmMYB35 promoted anthocyanin biosynthesis in plants. The results provide new insights into the regulatory effects of SmMYB35 on key anthocyanin biosynthetic genes and advance our understanding of the molecular mechanism of light-induced anthocyanin synthesis in eggplants.

SmBICs Inhibit Anthocyanin Biosynthesis in Eggplant (Solanum melongena L.)

Eggplant is rich in anthocyanins, which are thought to be highly beneficial for human health. It has been reported that blue light inhibitors of cryptochromes (BICs) act as negative regulators in light signal transduction, but little is known about their role in anthocyanin biosynthesis. In this study, yeast one-hybrid analysis showed that SmBICs could bind to the promoter of SmCHS, indicating that they could directly participate in eggplant anthocyanin biosynthesis. In SmBICs-silenced eggplants, more anthocyanins were accumulated, while SmBIC1-overexpression (OE) and SmBIC2-OE Arabidopsis and eggplants synthesized less anthocyanin. Quantitative real-time polymerase chain reaction also revealed that the anthocyanin structural genes, which were downregulated in SmBIC1-OE and SmBIC2-OE lines, were upregulated in SmBICs-silenced eggplants. In addition, transcriptome analysis further confirmed that differentially expressed genes of SmBICs-OE plants were enriched mainly in the pathways related to anthocyanin biosynthesis and the key transcription factors and structural genes for anthocyanin biosynthesis, such as SmMYB1, SmTT8, SmHY5, SmCHS, SmCHI, SmDFR and SmANS, were suppressed significantly. Finally, bimolecular fluorescence complementation and blue-light-dependent degradation assay suggested that SmBICs interacted with photo-excited SmCRY2 to inhibit its photoreaction, thereby inhibiting the expression of genes related to anthocyanin biosynthesis and reducing anthocyanin accumulation. Collectively, our study suggests that SmBICs repress anthocyanin biosynthesis by inhibiting photoactivation of SmCRY2. This study provides a new working model for anthocyanin biosynthesis in eggplant.

Genome-wide characterization and expression analysis of AP2/ERF genes in eggplant (Solanum melongena L.)

The AP2/ERF (APETALA2/Ethylene Response Factor) transcription factor superfamily plays crucial roles in a slew of physiological processes, such as plant growth and development, stress response, and secondary metabolites biosynthesis. Eggplant, especially the one rich with anthocyanins, is an economically important horticultural vegetable cultivated worldwide. In this study, we comprehensively analyzed the putative AP2/ERF gene family members and their response to abiotic stress in eggplant. As per the phylogenetic, conserved domains, and motif analysis, 178 AP2/ERF genes in this study belonged to five subfamilies. Chromosomal distributions analysis elucidated stochastic distribution of 178 putative SmAP2/ERF genes across the twelve chromosomes of eggplant. Expression profiles of sixteen selected AP2/ERF genes response to low temperature, drought, salt, abscisic acid, and ethylene treatments were analyzed, which revealed the involvement of SmAP2/ERF genes in diverse signaling pathways. In addition, we integrated RNA-Seq data on anthocyanin biosynthesis in eggplant with yeast one-hybrid and dual-luciferase assays and identified involvement of the SmAP2/ERF genes (Smechr0902114.1 and Smechr1102075.1) in the regulation of anthocyanin biosynthesis. This study will enable further functional characterization of AP2/ERF genes in eggplant and extend the current understanding of the role played by AP2/ERF genes in anthocyanin biosynthesis regulation.

A SmelAAT Acyltransferase Variant Causes a Major Difference in Eggplant (Solanum melongena L.) Peel Anthocyanin Composition

Eggplant berries are rich in anthocyanins like delphinidin-3-rutinoside (D3R) and nasunin (NAS), which are accumulated at high amounts in the peel. NAS is derived by D3R through acylation and glycosylation steps. The presence of D3R or NAS is usually associated with black-purple or lilac fruit coloration of the most cultivated varieties, respectively. Building on QTL mapping position, a candidate gene approach was used to investigate the involvement of a BAHD anthocyanin acyltransferase (SmelAAT) in determining anthocyanin type. The cDNA sequence comparison revealed the presence of a single-base deletion in D3R-type line ‘305E40’ (305E40_aat) with respect to the NAS-type reference line ‘67/3’. This is predicted to cause a frame shift mutation, leading to a loss of SmelAAT function and, thus, D3R retention. RT-qPCR analyses confirmed SmelAAT and 305E40_aat expression during berry maturation. In D3R-type lines, ‘305E40’ and ‘DR2’, overexpressing the functional SmelAAT allele from ‘67/3’, the transcript levels of the transgene correlated with the accumulation of NAS in fruit peel. Furthermore, it was also found a higher expression of the transcript for glucosyltransferase Smel5GT1, putatively involved with SmelAAT in the last steps of anthocyanin decoration. Finally, an indel marker matching with anthocyanin type in the ‘305E40’ × ’67/3’ segregating population was developed and validated in a wide number of accessions, proving its usefulness for breeding purposes.

Weighted gene co-expression network analysis identifies genes related to anthocyanin biosynthesis and functional verification of hub gene SmWRKY44

Eggplant is rich in anthocyanins, which are thought to be highly beneficial for human health. There is no study on weighted gene co-expression network analysis (WGCNA) of anthocyanin biosynthesis in eggplant. Here, transcriptome data of 33 eggplant pericarp samples treated with light were used for WGCNA to identify significant modules. Total 13000 DEGs and 12 modules were identified, and the most significant module was associated with the secondary metabolites pathways. In addition, the hub gene SmWRKY44 with high connectivity was selected and its function was verified. The expression of SmWRKY44 showed a significant correlation with anthocyanin accumulation in the eggplant peels, leaves, and flowers. SmWRKY44-OE Arabidopsis significantly increased the accumulation of anthocyanins. Yeast two-hybrid and BiFC assays showed that SmWRKY44 could interact with SmMYB1, and it was also found that they could jointly promote the biosynthesis of anthocyanins in eggplant leaves through transient expression analysis. Our work provides a new direction for studying the molecular mechanism of light-induced anthocyanin biosynthesis in eggplant.

Nutritional deficiency in scarlet eggplant limits its growth by modifying the absorption and use efficiency of macronutrients

The intensity damages caused by nutritional deficiency in growing plants can vary with nutrients. The effects caused by nutrient omission in the plant nutritional efficiency in relation to the absorption and use of the missing nutrient, and the reasons why these damages reflect in other nutrients have not yet been reported in the culture of scarlet eggplant. A better understanding of the nutritional mechanisms involved may clarify why certain nutrients cause greater limitations than other during plants growth. Thus, this study was designed with the aim of evaluating the damages caused by macronutrients deficiency in the culture of scarlet eggplant in the accumulation of these nutrients, nutritional deficiency, plants growth and in visual symptoms. The experiment was carried out in a controlled environment where plants were cultivated in a hydroponic system. Treatments consisted of supplying a complete Hoagland and Arnon solution (CS), and other nutrient solutions with individual omissions of nitrogen (-N), phosphorus (-P), potassium (-K), calcium (-Ca), magnesium (-Mg) and sulphur (-S). When a nutrient deficiency arose, nutritional analyses, growth and visual symptoms were analyzed. The omissions of N, S and K in the nutrient solution resulted in lower accumulation of all macronutrients in both the above and below ground biomass. Individual omissions resulted in nutritional imbalances with reflexes in the absorption efficiencies and use of the missing nutrient, as well as of other nutrients, revealing that the metabolism involves multiple nutritional interactions. Losses of nutritional efficiencies of macronutrients caused detrimental effects on plants growth, with reduced height, stem diameter, number of leaves, leaf area, and biomass production in above ground and below ground. From the losses in production in above ground biomass, the order of macronutrients limitation was N, S, K, Ca, Mg, and P, with reductions of 99, 96, 94, 76, 51 and 46%, respectively, in comparison to plants cultivated in CS. The most limiting nutrients were N, S, and K, seen that its deficiencies affected the metabolism of all other nutrients. This study demonstrates the importance of an adequate nutritional management of N, S, and K in the cultivation of scarlet eggplant.

Functional characterization of SmMYB86, a negative regulator of anthocyanin biosynthesis in eggplant (Solanum melongena L.)

Anthocyanins are a group of secondary metabolites that protect plants from biotic and abiotic stresses. The research on anthocyanins has been well-received due to their colorfulness and human health benefits. In this study, we used the photosensitive eggplant cultivar 'Lanshan Hexian' as the research material and reported the functional characterization of SmMYB86, a negative regulator involved in the anthocyanin biosynthesis in eggplant. Our results suggested that SmMYB86 was a nuclear protein that was particularly expressed in leaves, stems, and peels. Overexpression of SmMYB86 in eggplant indicated that the accumulation of anthocyanins was reduced. Silencing of SmMYB86 in eggplant fruit peel significantly increased the anthocyanin content and expression levels of SmCHS, SmF3H, and SmANS. Yeast one-hybrid and dual-luciferase assays showed that SmMYB86 could directly bind to the promoters of SmCHS, SmF3H, and SmANS and suppress their activities. SmTTG1 binded to the promoter of SmCHS and promoted its activating. SmMYB86 interacted with SmTTG1 and inhibited its promotive role in SmCHS expression. This study provides some insights into the regulatory roles of SmMYB86 on key structural genes in the anthocyanin synthesis pathway in eggplant.

Characterization of Cultivated Eggplant and its Wild Relatives Based on Important Fruit Biochemical Traits

BACKGROUND AND OBJECTIVES

The modern-day eggplant consumers desire varieties with a higher content of chlorogenic acid, but the cultivated varieties of eggplant are with a lower content of chlorogenic acid. Whereas, the wild relatives of eggplant are higher in phenolic acids. Therefore, this study characterized the cultivated eggplant and its wild relatives for the fruit dry matter content, total fruit phenolics and chlorogenic acid content.

MATERIALS AND METHODS

Fruits of the accessions of cultivated eggplant, one primary genepool species, nine secondary genepool species and three tertiary genepool species were characterized for dry matter content (%), total phenolics and the fruit chlorogenic acid content (mg g-1). The chlorogenic acid content in the fruit flesh was determined by using the High Performance Liquid Chromatography (HPLC).

RESULTS

Highest content of dry matter content of around 29% was determined for the species S. tomentosum and S. elaeagnifolium. Whereas, the highest content of total fruit phenolics were determined in the secondary genepool species S. linnaeanum. The most top content of chlorogenic acid around 4.5 mg g-1 of fruit dry weight was present in the species S. linnaeanum and S. torvum. Different clustering approaches were able to cluster the primary genepool species with the cultivated eggplant.

CONCLUSION

Overall, this work provides important information about the wild relatives of eggplant concerning their dry matter content, total phenolics and chlorogenic acid content. This information can be used to engineer eggplant varieties rich in fruit phenolics.

Reducing the nicotine content of tobacco by grafting with eggplant

BACKGROUND

Nicotine is a stimulant and potent parasympathomimetic alkaloid that accounts for 96-98% of alkaloid content. A reduction in the amount of nicotine in cigarettes to achieve a non-addictive level is necessary. We investigated whether replacing tobacco root with eggplant by grafting can restrict nicotine biosynthesis and produce tobacco leaves with ultra-low nicotine content, and analyzed the gene expression differences induced by eggplant grafting.

RESULTS

The nicotine levels of grafted tobacco leaves decreased dramatically. The contents of nornicotine, anabasine, NNN, NNK, NAT, total TSNAs and the nicotine of mainstream cigarette smoke decreased, and the contents of amino acids and the precursors of alkaloids increased in grafted tobacco. Eggplant grafting resulted in the differential expression of 440 genes. LOC107774053 had higher degrees in two PPI networks, which were regulated by LOC107802531 and LOC107828746 in the TF-target network.

CONCLUSIONS

Replacing tobacco root with eggplant by grafting can restrict nicotine biosynthesis and produce tobacco leaves with ultra-low or zero nicotine content. The differential expression of LOC107774053 may be associated with eggplant grafting.

Identification of a new R3 MYB type repressor and functional characterization of the members of the MBW transcriptional complex involved in anthocyanin biosynthesis in eggplant (S. melongena L.)

Here we focus on the highly conserved MYB-bHLH-WD repeat (MBW) transcriptional complex model in eggplant, which is pivotal in the transcriptional regulation of the anthocyanin biosynthetic pathway. Through a genome-wide approach performed on the recently released Eggplant Genome (cv. 67/3) previously identified, and reconfirmed by us, members belonging to the MBW complex (SmelANT1, SmelAN2, SmelJAF13, SmelAN1) were functionally characterized. Furthermore, a regulatory R3 MYB type repressor (SmelMYBL1), never reported before, was identified and characterized as well. Through a qPCR approach, we revealed specific transcriptional patterns of candidate genes in different plant tissue/organs at two stages of fruit development. Two strategies were adopted for investigating the interactions of bHLH partners (SmelAN1, SmelJAF13) with MYB counterparts (SmelANT1, SmelAN2 and SmelMYBL1): Yeast Two Hybrid (Y2H) and Bimolecular Fluorescent Complementation (BiFC) in A. thaliana mesophylls protoplast. Agro-infiltration experiments highlighted that N. benthamiana leaves transiently expressing SmelANT1 and SmelAN2 showed an anthocyanin-pigmented phenotype, while their co-expression with SmelMYBL1 prevented anthocyanin accumulation. Our results suggest that SmelMYBL1 may inhibits the MBW complex via the competition with MYB activators for bHLH binding site, although this hypothesis requires further elucidation.

Genetic variation in eggplant for Nitrogen Use Efficiency under contrasting NO3 - supply

Eggplant (Solanum melongena L.) yield is highly sensitive to N fertilization, the excessive use of which is responsible for environmental and human health damage. Lowering N input together with the selection of improved Nitrogen-Use-Efficiency (NUE) genotypes, more able to uptake, utilize, and remobilize N available in soils, can be challenging to maintain high crop yields in a sustainable agriculture. The aim of this study was to explore the natural variation among eggplant accessions from different origins, in response to Low (LN) and High (HN) Nitrate (NO₃ ^- ) supply, to identify NUE-contrasting genotypes and their NUE-related traits, in hydroponic and greenhouse pot experiments. Two eggplants, AM222 and AM22, were identified as N-use efficient and inefficient, respectively, in hydroponic, and these results were confirmed in a pot experiment, when crop yield was also evaluated. Overall, our results indicated the key role of N-utilization component (NUtE) to confer high NUE. The remobilization of N from leaves to fruits may be a strategy to enhance NUtE, suggesting glutamate synthase as a key enzyme. Further, omics technologies will be used for focusing on C-N metabolism interacting networks. The availability of RILs from two other selected NUE-contrasting genotypes will allow us to detect major genes/quantitative trait loci related to NUE.

Interventions of aqueous extract of Solanum melongena fruits (garden eggs) on mercury chloride induced testicular toxicity in adult male Wistar rats

BACKGROUND

Solanum melongena (SM) is commonly known as the garden egg fruit or eggplant. It can be eaten fresh or cooked and has a large history of consumption in West Africa. This study focused on interventions of aqueous extract of SM (garden eggs) fruits on Mercury chloride (HgCl2) induced testicular toxicity in adult male Wistar rats.

METHODS

Thirty-two adult male Wistar rats were randomly divided into four groups (A-D) of eight (n = 8) rats each. Group A Served as control and was given 10 ml/kg/day of distilled water, Group B- 500 mg/kg B.W of SM, Group C received 40 mg/kg B.W HgCl2 and Group D- 500 mg/kg B.W of SM and 40 mg/kg B.W HgCl2). The administration was done by gastric gavage once a day, for twenty-eight consecutive days. Testicular weight, semen analysis revealing the sperm count and sperm motility were assessed, gross parameters of the testis and testicular histology were assessed. Testicular oxidative stress markers viz a viz malondialdehyde (MDA), superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and reduced glutathione (GSH) were also assessed.

RESULTS

assessment of the histological profiles of the testes showed a derangement of the cytoarchitecture and deterioration of sperm quality after HgCl2 administration and a marked improvement was observed after SM administration. Similarly, SM was associated with increased antioxidant parameters (SOD, CAT, GPx, and GSH) and decreased MDA in SM + HgCl2 rats.

CONCLUSION

It was concluded that S. melongena offers protection against free radical mediated oxidative stress of rats with mercury chloride induced testicular toxicity.

Indole-3-acetic acid promotes cadmium (Cd) accumulation in a Cd hyperaccumulator and a non-hyperaccumulator by different physiological responses

To study the effects of indole-3-acetic acid (IAA) on cadmium (Cd) accumulation and the physiological responses of the Cd hyperaccumulator Solanum nigrum and non-hyperaccumulator Solanum melongena, a pot experiment was conducted in soil containing 2 mg kg^-1 Cd in which different concentrations of IAA (0, 10, 20, or 40 mg L^-1) were sprayed on plant leaves. The results showed that Cd accumulation in shoots of S. nigrum was significantly increased by 30% after the addition of 10 mg L^-1 IAA under 2 mg kg^-1 Cd stress compared to that in the control, but shoot Cd accumulation showed no significant change in S. melongena after this IAA treatment. Additionally, the growth and the proline content in the two species were significantly increased by 20 mg L^-1 IAA. The activities of peroxidase and catalase in leaves of S. nigrum and the activity of superoxide dismutase (SOD) in S. melongena were significantly increased and their malondialdehyde content was significantly decreased compared to those in the control. The root activity of S. nigrum was significantly improved after 10 and 20 mg L^-1 IAA treatments, but no significant difference was observed in S. melongena. The correlation analysis results showed that the Cd concentration in leaves of S. nigrum was significantly and positively correlated with the carotenoid and proline contents, and there was also a significant positive correlation between the Cd concentration and SOD activity in leaves of S. melongena. Therefore, S. nigrum is an ideal plant for the phytoextraction of Cd-contaminated soil assisted by IAA. IAA promotes Cd accumulation in plant shoots by enhancing the accumulation of carotenoids and proline in S. nigrum and maintaining a high leaf SOD activity in S. melongena.

CBFs Function in Anthocyanin Biosynthesis by Interacting with MYB113 in Eggplant (Solanum melongena L.)

Eggplant is rich in anthocyanins. R2R3-MYB transcription factors play a key role in the anthocyanin pathway. Low temperature is vital abiotic stress that affects the anthocyanin biosynthesis in plants. CBFs (C-repeat binding factors) act as central regulators in cold response. In this study, we found that SmCBF1, SmCBF2 and SmCBF3, via their C-terminal, physically interacted with SmMYB113, a key regulator of anthocyanin biosynthesis in eggplant. SmCBF2 and SmCBF3 upregulated the expression of SmCHS and SmDFR via a SmMYB113-dependent pathway. In addition, the transient expression assays demonstrated that co-infiltrating SmCBFs and SmMYB113 significantly improved the contents of anthocyanin and the expression levels of anthocyanin structural genes in tobacco. When SmTT8, a bHLH partner of SmMYB113, coexpressed with SmCBFs and SmMYB113, the anthocyanin contents were significantly enhanced compared with SmCBFs and SmMYB113. Furthermore, overexpression of SmCBF2 and SmCBF3 could facilitate the anthocyanin accumulation under cold conditions in Arabidopsis. Taken together, these results shed light on the functions of SmCBFs and potential mechanisms of low-temperature-induced anthocyanin biosynthesis in eggplant.

A highly efficient organogenesis protocol based on zeatin riboside for in vitro regeneration of eggplant

BACKGROUND

Efficient organogenesis induction in eggplant (Solanum melongena L.) is required for multiple in vitro culture applications. In this work, we aimed at developing a universal protocol for efficient in vitro regeneration of eggplant mainly based on the use of zeatin riboside (ZR). We evaluated the effect of seven combinations of ZR with indoleacetic acid (IAA) for organogenic regeneration in five genetically diverse S. melongena and one S. insanum L. accessions using two photoperiod conditions. In addition, the effect of six different concentrations of indolebutyric acid (IBA) in order to promote rooting was assessed to facilitate subsequent acclimatization of plants. The ploidy level of regenerated plants was studied.

RESULTS

In a first experiment with accessions MEL1 and MEL3, significant (p < 0.05) differences were observed for the four factors evaluated for organogenesis from cotyledon, hypocotyl and leaf explants, with the best results obtained (9 and 11 shoots for MEL1 and MEL3, respectively) using cotyledon tissue, 16 h light / 8 h dark photoperiod conditions, and medium E6 (2 mg/L of ZR and 0 mg/L of IAA). The best combination of conditions was tested in the other four accessions and confirmed its high regeneration efficiency per explant when using both cotyledon and hypocotyl tissues. The best rooting media was R2 (1 mg/L IBA). The analysis of ploidy level revealed that between 25 and 50% of the regenerated plantlets were tetraploid.

CONCLUSIONS

An efficient protocol for organogenesis of both cultivated and wild accessions of eggplant, based on the use of ZR, is proposed. The universal protocol developed may be useful for fostering in vitro culture applications in eggplant requiring regeneration of plants and, in addition, allows developing tetraploid plants without the need of antimitotic chemicals.

Identification of DNA methyltransferases and demethylases in Solanum melongena L., and their transcription dynamics during fruit development and after salt and drought stresses

DNA methylation through the activity of cytosine-5-methyltransferases (C5-MTases) and DNA demethylases plays important roles in genome protection as well as in regulating gene expression during plant development and plant response to environmental stresses. In this study, we report on a genome-wide identification of six C5-MTases (SmelMET1, SmelCMT2, SmelCMT3a, SmelCMT3b, SmelDRM2, SmelDRM3) and five demethylases (SmelDemethylase_1, SmelDemethylase_2, SmelDemethylase_3, SmelDemethylase_4, SmelDemethylase_5) in eggplant. Gene structural characteristics, chromosomal localization and phylogenetic analyses are also described. The transcript profiling of both C5-MTases and demethylases was assessed at three stages of fruit development in three eggplant commercial F1 hybrids: i.e. 'Clara', 'Nite Lady' and 'Bella Roma', representative of the eggplant berry phenotypic variation. The trend of activation of C5-MTases and demethylase genes varied in function of the stage of fruit development and was genotype dependent. The transcription pattern of C5MTAses and demethylases was also assessed in leaves of the F1 hybrid 'Nite Lady' subjected to salt and drought stresses. A marked up-regulation and down-regulation of some C5-MTases and demethylases was detected, while others did not vary in their expression profile. Our results suggest a role for both C5-MTases and demethylases during fruit development, as well as in response to abiotic stresses in eggplant, and provide a starting framework for supporting future epigenetic studies in the species.

Comparative analysis of the responses to water stress in eggplant (Solanum melongena) cultivars

Little information is available on the physiological and biochemical responses to water stress in eggplant (Solanum melongena). We evaluated four genetically diverse eggplant varieties (MEL3-MEL6) under control and water stress conditions. Measurements were taken for plant growth, tissue water content, levels of chlorophylls a and b, carotenoids, proline, malondialdehyde, total phenolics, total flavonoids, superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione reductase (GR) activities. For most traits, the water stress treatment had a greater contribution than the variety effect to the total sums of squares in an ANOVA analysis, except for total flavonoids, SOD, APX, and GR. The water stress treatment had a strong effect on plant growth and tissue water content. In general, water stress reduced the three photosynthetic pigments, increased proline, malondialdehyde, total phenolics, and total flavonoids, although some varietal differences were observed. Different patterns were also detected in the activities of the four enzymes evaluated, but few differences were observed for individual varieties between the control and water stress treatments. Many significant phenotypic correlations were observed among the traits studied, but only eight environmental correlations were detected. A PCA analysis distinctly separated individuals according to the treatment, and revealed a clearer separation of varieties under water stress than under control conditions, pointing to varietal differences in the responses to stress. Our results suggest that proline could be used as a marker for drought stress tolerance in this species. The information obtained provides new insight on the physiological and biochemical responses of eggplant to drought stress.

Transcriptome analysis revealed expression of genes related to anthocyanin biosynthesis in eggplant (Solanum melongena L.) under high-temperature stress

BACKGROUND

Anthocyanin synthesis is affected by many factors, among which temperature is an important environmental factor. Eggplant is usually exposed to high temperatures during the cultivation season in Shanghai, China. Therefore,RNA -seq analysis was used to determine the effects of high-temperature stress on gene expression in the anthocyanin biosynthetic pathway of eggplant (Solanum melongena L.).

RESULTS

We tested the heat-resistant cultivar 'Tewangda'. The plants were incubated at 38 °C and 45 °C, and the suitable temperature for eggplant growth was used as a control. The treatment times were 3 h and 6 h. The skin of the eggplant was taken for transcriptome sequencing, qRT-PCR assays and bioinformatic analysis. The results showed that 770 genes were differentially expressed between different treatments. Gene Ontology (GO) database and Kyoto Encyclopedia of Genes and Genomes (KEGG) database analyses identified 16 genes related to anthocyanin biosynthesis, among which CHSB was upregulated. Other genes, including BHLH62, MYB380, CHI3, CHI, CCOAOMT, AN3, ACT-2, HST, 5MA-T1, CYP75A2, ANT17, RT, PAL2, and anthocyanin 5-aromatic acyltransferase were downregulated. In addition, the Myb family transcription factor PHL11 was upregulated in the CK 3 h vs 45 °C 3 h, CK 3 h vs 38 °C 3 h, and CK 6 h vs 38 °C 6 h comparisons, and the transcription factor bHLH35 was upregulated in the CK 3 h vs 38 °C 3 h and CK 6 h vs 38 °C 6 h comparisons.

CONCLUSION

These results indicated that high temperature will downregulate most of the genes in the anthocyanin biosynthetic pathway of eggplant. Our data have a reference value for the heat resistance mechanism of eggplant and can provide directions for molecular breeding of heat-resistant germplasm with anthocyanin content in eggplant.

Comparative transcription analysis of photosensitive and non-photosensitive eggplants to identify genes involved in dark regulated anthocyanin synthesis

BACKGROUND

Light is a key environmental factor in regulation of anthocyanin biosynthesis. Through a large number of bagging screenings, we obtained non-photosensitive eggplants that still have decent amount of anthocyanin synthesized after bagging. In the present study, transcriptome was made to explore the molecular mechanism of dark-regulated anthocyanin synthesis in non-photosensitive eggplant.

RESULTS

The transcriptome of the pericarp at 0 h, 0.5 h, 4 h, and 8 h after bag removal were sequenced and analyzed. Comparison of the sequencing data with those of photosensitive eggplant for the same time period showed that anthocyanin synthesis genes had different expression trends. Based on the expression trends of the structural genes, it was discovered that 22 transcription factors and 4 light signal transduction elements may be involved in the anthocyanin synthesis in two types of eggplants. Through transcription factor target gene prediction and yeast one-hybrid assay, SmBIM1, SmAP2, SmHD, SmMYB94, SmMYB19, SmTT8, SmYABBY, SmTTG2, and SmMYC2 were identified to be directly or indirectly bound to the promoter of the structural gene SmCHS. These results indicate that the identified 9 genes participated in the anthocyanin synthesis in eggplant peel and formed a network of interactions among themselves.

CONCLUSIONS

Based on the comparative transcription, the identified 22 transcription factors and 4 light signal transduction elements may act as the key factors in dark regulated anthocyanin synthesis in non-photosensitive eggplant. The results provided a step stone for further analysis of the molecular mechanism of dark-regulated anthocyanin synthesis in non-photosensitive eggplant.

Management of chromium (VI) toxicity by calcium and sulfur in tomato and brinjal: Implication of nitric oxide

To reduce pressure of toxic metals on crop plants, several strategies are being employed of which nutrient management is gaining much importance. Moreover, whether nitric oxide (NO), has any role in nutrients-mediated management/amelioration of metal toxicity is still not known. Therefore, the role of Ca and S in managing Cr(VI) toxicity was investigated in tomato and brinjal with an emphasis on possible involvement of NO. Cr(VI) reduced growth in both vegetables which was accompanied by increased accumulation of Cr(VI), lignin and reactive oxygen species (ROS), and altered cell cycle dynamics and photochemistry of photosynthesis. However, external addition of either Ca or S reversed these effects and hence improved growth noticed in both vegetables. Cr(VI) toxicity was further increased by NG-nitro-l-arginine methyl ester even with additional Ca and S while sodium nitroprusside either restored growth up to the control level or increased it in both vegetables, even in the presence of L-NAME, suggesting that NO might have a positive role in nutrients-mediated management/amelioration of Cr(VI) toxicity. In this study, role of Ca, S and NO with reference to Cr(VI) and NO accumulation, components of phenylpropanoid pathway, cell cycle dynamics, photosynthesis, ROS and antioxidant potential in managing Cr(VI) toxicity is discussed.

A novel hydroxycinnamoyl transferase for synthesis of hydroxycinnamoyl spermine conjugates in plants

BACKGROUND

Hydroxycinnamoyl-spermine conjugates (HCSpm) are a class of hydroxycinnamic acid amides (HCAAs), which not only are instrumental in plant development and stress response, but also benefit human health. However, HCSpm are not commonly produced in plants, and the mechanism of their biosynthesis remains unclear. In previous investigations of phenolics in Solanum fruits related to eggplant (Solanum melongena L.), we discovered that Solanum richardii, an African wild relative of eggplant, was rich in HCSpms in fruits.

RESULTS

The putative spermine hydroxycinnamoyl transferase (HT) SpmHT was isolated from S. richardii and eggplant. SrSpmHT expression was high in flowers and fruit, and was associated with HCSpm accumulation in S. richardii; however, SpmHT was hardly detected in eggplant cultivars and other wild relatives. Recombinant SpmHT exclusively selected spermine as the acyl acceptor substrate, while showing donor substrate preference in the following order: caffeoyl-CoA, feruloyl-CoA, and p-coumaroyl-CoA. Molecular docking revealed that substrate binding pockets of SpmHT could properly accommodate spermine but not the shorter, more common spermidine.

CONCLUSION

SrSpmHT is a novel spermine hydroxycinnamoyl transferase that uses Spm exclusively as the acyl acceptor substrate to produce HCSpms. Our findings shed light on the HCSpm biosynthetic pathway that may allow an increase of health beneficial metabolites in Solanum crops via methods such as introgression or engineering HCAA metabolism.

Effects of grafting on root-to-shoot cadmium translocation in plants of eggplant (Solanum melongena) and tomato (Solanum lycopersicum)

Heavy metal cadmium (Cd) pollution in farmland has become a serious threat to food security globally. In this work, a grafting technique was applied to eggplant (Solanum melongena) and tomato (Solanum lycopersicum) plants using Solanum torvum as rootstock to investigate effects of grafting on Cd accumulation in shoots. The un-grafted, self-grafted, and grafted plants were grown in soils containing 2 mg kg^-1 Cd. Results showed that grafting on S. torvum could efficiently reduce Cd accumulation in leaves of eggplant and tomato, and the decrease was 89% and 72%, respectively. With S. torvum as rootstock, Cd concentrations were 1.11 mg kg^-1 and 6.58 mg kg^-1 in leaves of grafted eggplant and tomato, which were significantly decreased as compared with un-grafted plants (10.12 mg kg^-1 and 23.19 mg kg^-1, respectively, p < 0.05). In addition, Cd concentrations were 12.11 mg kg^-1 and 29.47 mg kg^-1 in leaves of self-grafted eggplant and tomato, respectively, which was similar to those in un-grafted eggplant, but more than those in un-grafted tomato (p < 0.05). This suggests that the S. torvum rootstock, and not the grafting operation, was responsible for efficient reduction of Cd accumulation in shoots of eggplant and tomato plants. Furthermore, total sulfur and sulfate (SO₄^2-) concentrations analysis revealed that there was a similar trend between Cd accumulation and total sulfur or SO₄^2- concentrations in leaves of plants tested. Additionally, a strong positive correlation between Cd accumulation and total sulfur or SO₄^2- concentrations occurred in leaves of eggplant and tomato plants. Thus, sulfur, mainly SO₄^2-, in leaves may play an important regulatory role in Cd accumulation of eggplant and tomato plants. This study provides the theoretical and technical support for applying grafting technique for the safe practice of farming in Cd-contaminated agricultural soil.

Promoting the productivity and quality of brinjal aligned with heavy metals immobilization in a wastewater irrigated heavy metal polluted soil with biochar and chitosan

Depleting aquifers, lack of planning and low socioeconomic status of Pakistani farmers have led them to use wastewater (WW) for irrigating their crops causing food contamination with heavy metals and ultimately negative effects on human health. This study evaluates the effects of chitosan (CH) and biochar (BC) on growth and nutritional quality of brinjal plant together with in situ immobilization of heavy metals in a soil polluted with heavy metals due to irrigation with wastewater (SPHIW) and further irrigated with the same WW. Both CH and BC were applied at three different rates i.e. low rate [(LR), BC0.5%, CH0.5% and BC0.25%+CH0.25%], medium rate [(MR), BC1%, CH1% and BC0.5%+CH0.5%] and high rate [(HR), BC1.5%, CH1.5% and BC0.75%+CH0.75%]. Result revealed that brinjal growth, antioxidant enzymes, and fruit nutritional quality significantly improved from LR to HR for each amendment, relative to control. However, these results were more prominent with BC alone and BC+CH, compared with CH alone at each rate. Similarly, with few exceptions, significant reduction in Ni, Cd, Co, Cr and Pb concentrations in the root, shoot and fruit were found in sole CH treatment both at LR and MR but in both CH and BC+CH treatments at HR, relative to control. Interestingly, the concentrations of Fe in the roots, shoots and fruit were more pronounced at BC treatments relative to CH and BC+CH treatments at each rate, compared to control. Overall, the BC+CH treatment at HR was the most effective treatment for in situ immobilization of heavy metals in SPHIW and further irrigated with the same WW, compared to rest of the treatments. This study indicates that BC0.75%+CH0.75% treatment can be used to reduce mobility and bioavailability of heavy metals in SPHIW and facilitates plant growth by improving the antioxidant system. However, the feasibility of BC0.75%+CH0.75% treatment should also be tested at the field scale.

Impact of Zinc oxide nanoparticles on eggplant (S. melongena): studies on growth and the accumulation of nanoparticles

The increasing use of nanoparticles and their occurrence in the environment has made it imperative to elucidate their impact on the environment. Although several studies have advanced the authors' understanding of nanoparticle-plant interactions, their knowledge of the exposure of plants to nanoparticles and their effects on edible crop plants remain meager and is often paradoxical. The aim of this study was to increase their knowledge on the effect of zinc oxide (ZnO) nanoparticles on eggplant seed germination and seedling growth. ZnO nanoparticles had a negative effect on the growth of eggplant in plant tissue-culture conditions, as the growth of seedlings decreased with the increase in the concentration of ZnO nanoparticles. In contrast, ZnO nanoparticles enhanced eggplant growth under greenhouse conditions. The accumulation of ZnO nanoparticles in various parts of eggplant was observed through scanning electron microscopy of both plant tissue-culture and greenhouse-raised eggplant seedlings. To the best of their knowledge, this is the first study to report on ZnO nanoparticle accumulation in eggplant and its effect on seed germination and seedling growth.

Metabolomic analyses to evaluate the effect of drought stress on selected African Eggplant accessions

BACKGROUND

Drought stress is one of the main abiotic stresses that affect crops. It leads to biochemical changes that can have adverse effects on plant growth, development and productivity. African eggplants are important vegetable and fruit crops reported to adapt and thrive well under drought stress. The diversified metabolites arising due to stress have not been well defined. A gas chromatographic-mass spectrometric metabolomic approach was applied to characterize the effect of drought stress on metabolites at different stages of growth. Nineteen accessions were selected for analysis and drought was imposed by withholding water until soil moisture reached 60% field capacity. Fresh leaf tissues were sampled before stress, 2 and 4 weeks after stress and metabolite profiling done.

RESULTS

Significant changes in metabolite content were observed, and potentially important metabolites with respect to stress responses were characterized. Proline, glutamate, sucrose, fructose and tricarboxylic acid cycle metabolites were shown to be positively correlated with stress. Principal component analysis showed a clear discrimination between the different accessions, growth stages and stress/control conditions.

CONCLUSION

The results illustrate that drought stress has a significant impact on the concentrations of some metabolites, such as amino acids, sugars and organic acids, which may contribute to drought stress effects and tolerance. © 2017 Society of Chemical Industry.

The role of phytochromes in regulating biosynthesis of sterol glycoalkaloid in eggplant leaves

Glycoalkaloids are toxic compounds that are synthesized by many Solanum species. Glycoalkaloid biosynthesis is influenced by plant genetic and environmental conditions. Although many studies have shown that light is an important factor affecting glycoalkaloid biosynthesis, the specific mechanism is currently unknown. Chlorophyll and carotenoid biosynthesis depend on light signal transduction and share some intermediate metabolites with the glycoalkaloid biosynthetic pathway. Here, we used virus-induced gene silencing to silence genes encoding phytoene desaturase (PDS) and magnesium chelatase (CHLI and CHLH) to reduce chlorophyll and carotenoid levels in eggplant leaves. Quantification of carotenoid and chlorophyll levels is analyzed by LC/PDA/APCI/MS and semipolar metabolite profiling by LC/HESI/MS. Notably, the resulting lines showed decreases in glycoalkaloid production. We further found that the expression of some genes involved in the production of glycoalkaloids and other metabolites were suppressed in these silenced lines. Our results indicate that photosynthetic pigment accumulation affects steroidal glycoalkaloid biosynthesis in eggplant leaves. This finding lays the foundation for reducing the levels of endogenous antinutritional compounds in crops.

Combined transcriptomic and proteomic analysis constructs a new model for light-induced anthocyanin biosynthesis in eggplant (Solanum melongena L.)

Light is a key environmental factor affecting anthocyanin biosynthesis. Our previous study demonstrated that "Lanshan Hexian" is a light-sensitive eggplant cultivar, but its regulatory mechanism is unknown. Here, delphinidin-3-[4-(cis-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside and delphinidin-3-[4-(trans-p-coumaroyl)-rhamnosyl-glucopyranoside]-5-glucopyranoside were identified as the main anthocyanin components in Lanshan Hexian by ultra-performance liquid chromatography-tandem mass spectrometry. Three time points of anthocyanin accumulation, including the start point (0 day), fastest point (5 days), and highest point (12 day), were investigated by using ribonucleic acid sequencing and iTRAQ technology. The corresponding correlation coefficients of differentially expressed genes, and differentially expressed proteins were 0.6936, 0.2332, and 0.6672. Anthocyanin biosynthesis was a significantly enriched pathway, and CHI, F3H, 3GT, 5GT, and HY5 were regulated at both transcriptional and translational levels. Moreover, some transcription factors and photoreceptors may participate in light-induced anthocyanin biosynthesis like the known transcription factors MYB113 and TT8. The transient expression assay indicated that SmMYB35, SmMYB44, and a SmMYB86 isoform might involve in the light-induced anthocyanin biosynthesis pathway. Finally, a regulatory model for light-induced anthocyanin biosynthesis in eggplant was constructed. Our work provides a new direction for the study of the molecular mechanisms of light-induced anthocyanin biosynthesis in eggplant.

A spiking strategy facilitates housekeeping selection for RT-qPCR analysis under different biotic stresses in eggplant

Endogenous housekeeping genes are traditionally employed to normalize the expression of target genes in RT-qPCR studies. Assuming that a perfect housekeeping suitable for every condition does not exist, expression stability of the chosen reference gene should be evaluated at every new experiment. The housekeeping selection process reveals furthermore complicated and time-consuming when different conditions have to be compared in the same experimental dataset. As an alternative strategy, we spiked an external reference transcript (ERT) into all RNA samples of our dataset (eggplant roots subjected to different biotic stresses), and used it to normalize the expression levels of native candidate housekeeping. ERT expression resulted highly stable across all samples and enabled to indicate glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as the most stable endogenous housekeeping. This result was confirmed by the use of GeNorm, Normfinder, and BestKeeper algorithms. This method might be generally applied to expedite the selection process of the best reference gene.