Metabolomic Analysis Identifies Differences Between Wild and Domesticated Chili Pepper Fruits During Development (Capsicum annuum L.)

Metabolite profiling reveals differential accumulation of secondary metabolites related to flavour and colour across four heirloom chilli landraces

Chillies from Northeast India exhibit wide variability in fruit morphology, pungency, bearing habit and crop duration. An untargeted metabolite profiling using LC-HRMS of four 'heirloom' pungent landraces viz. Naga chilli (AL-1), Dalle khursani (AL-2), Sohmynken khnai (AL-3), and J-41(B) was performed and compared with Kashi anmol (KA). While AL-2, J-41(B) and KA belong to C. annuum species, AL-1 is categorised as C. chinense and AL-3 is C. frutescens. A total of 6990 consistent peaks of monoisotopic masses were detected, out of which 2702 metabolites were identified using accurate mass error < 10 ppm. A higher number of differentially accumulated metabolites were seen in J-41(B) versus AL-3 (1376), followed by J-41(B) versus AL-2 (1365), J-41(B) versus AL-1 (1257), KA versus AL-2 (649), AL-3 versus KA (616), KA versus AL-1 (594) and J-41(B) versus KA (413). Variation among species was higher than variation within species. Pathway analysis identified fatty acid, carotenoid, flavonoid and capsaicinoid as key pathways. We identified eight major categories of metabolites, including fatty acids, sterol lipids, and flavonoids, which together account for over 70% of the significantly expressed metabolites across the genotypes. This study explores untargeted metabolites in various chilli species, offering insights into the biochemical and molecular mechanisms which may play a role in governing important fruit traits. Identification of key metabolites and underlying alleles for twenty-one genes across three pathways (flavonoid, capsaicinoid and carotenoid) suggests that the metabolites and associated alleles identified in this study can be used as biomarkers for further characterization of these heirloom chilli and could provide distinct parameter(s) in distinguishing improved cultivars from landraces. This will contribute towards breeding programs in aiding selection of fruits of the desirable traits.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-025-01576-4.

Multi-omics analysis of non-pungent (Capsicum annuum) and fiery hot ghost chili (C. chinense) provides insights into proteins involved in fruit development and metabolites biosynthesis

Global omics offer extensive insights into the diversity of essential biomolecules across various plant developmental stages. Despite advancements in high-throughput technologies, the integrated analysis of global omics such as proteomics, transcriptomics, and metabolomics, is yet to be fully explored in fruits of Capsicum species. In this study, we used an integrated omics approach to identify proteins involved in fruit development, and metabolite biosynthesis in the placenta and pericarp tissues of two contrasting genotypes belonging to ghost chili (Capsicum chinense) and C. annuum. The mass spectrometry analysis identified a total of 4,473 and 2,012 proteins from the pericarp and placenta tissues of Capsicum fruits. We observed expression of developmental stage-specific proteins, such as kinases, transferases, ion transporters, F-box proteins, and transcription factors that were enriched in the biosynthesis of primary and secondary metabolites. The abundance of these proteins corresponded with RNAseq data. Key proteins related to capsaicinoids biosynthesis, such as Acyltransferase 3, 3-oxoacyl-[acyl-carrier protein], 4-coumaroyl co-A ligase, and 3-ketoacyl-coA synthase 3, were identified in placenta of highly pungent ghost chili, along with J-domain proteins and transcription factors such as MYB101, MYB 14-like, bHLH112, NAC, and Cyt p450 CYP82D47, suggesting their role in capsaicinoids and secondary metabolites biosynthesis. Further, we observed a correlation of the expression of genes and proteins with the abundance of primary and secondary metabolites, such as carbohydrates, alcohols, fatty acids, phenolics, glycerides, polyamines, and amino acids. Our findings provide a novel multiomics resources for future functional studies, with potential applications in breeding programs.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s12298-025-01581-7.

Genome-Wide Identification and Characterization of SNPs and InDels of Capsicum annuum var. glabriusculum from Mexico Based on Whole Genome Sequencing

Capsicum annuum var. glabriusculum is an economically important horticultural crop and is considered the wild genetic ancestor of chili peppers. The distribution range extends from southern North America, through Central America, to South America. Approximately 226 million 150 paired-end reads were generated from CHMX_Ch1 (a C. annuum from Chihuahua, Mexico). To compare with the CHMX_Ch1 genome, high-quality reads from QO (a C. annuum from Querétaro, Mexico) were downloaded from the NCBI database. A total of 210,324 variants were detected in CHMX_Ch1, whereas 169,718 variants were identified in QO, all compared to the domesticated C. annuum reference genome, UCD10Xv1.1. This comprised 203,990 SNPs and 6334 InDels in CHMX_Ch1 and 164,955 SNPs and 4763 InDels in QO. The variants with high and moderate impact were identified as missense, splice acceptor, splice donor, start lost, stop gain, stop lost, frameshift, insertion, and deletion effects. The candidate genes with the highest fold enrichment values among the SNPs were predominantly involved in gene regulation and metabolic processes. InDels were associated with nuclear and transcriptional regulator activity in both genomes. Overall, a greater number of variants were found in CHMX_Ch1 compared to QO. This study provides knowledge of the principal functions associated with high- and moderate-impact variants and supplies a resource for further investigations of the genetic characteristics of these chiltepin peppers.

The Influence of Different Factors on the Metabolism of Capsaicinoids in Pepper (Capsicum annuum L.)

Pepper is a globally cultivated vegetable known for its distinct pungent flavor, which is derived from the presence of capsaicinoids, a class of unique secondary metabolites that accumulate specifically in pepper fruits. Since the accumulation of capsaicinoids is influenced by various factors, it is imperative to comprehend the metabolic regulatory mechanisms governing capsaicinoids production. This review offers a thorough examination of the factors that govern the metabolism of capsaicinoids in pepper fruit, with a specific focus on three primary facets: (1) the impact of genotype and developmental stage on capsaicinoids metabolism, (2) the influence of environmental factors on capsaicinoids metabolism, and (3) exogenous substances like methyl jasmonate, chlorophenoxyacetic acid, gibberellic acid, and salicylic acid regulate capsaicinoid metabolism. The findings of this study are expected to enhance comprehension of capsaicinoids metabolism and aid in the improvement of breeding and cultivation practices for high-quality pepper in the future.

Metabolomics of early blight (Alternaria solani) susceptible tomato (Solanum lycopersicum) unfolds key biomarker metabolites and involved metabolic pathways

Tomato (Solanum lycopersicum) is among the most important commercial horticultural crops worldwide. The crop quality and production is largely hampered due to the fungal pathogen Alternaria solani causing necrotrophic foliage early blight disease. Crop plants usually respond to the biotic challenges with altered metabolic composition and physiological perturbations. We have deciphered altered metabolite composition, modulated metabolic pathways and identified metabolite biomarkers in A. solani-challenged susceptible tomato variety Kashi Aman using Liquid Chromatography-Mass Spectrometry (LC-MS) based metabolomics. Alteration in the metabolite feature composition of pathogen-challenged (m/z 9405) and non-challenged (m/z 9667) plant leaves including 8487 infection-exclusive and 8742 non-infection exclusive features was observed. Functional annotation revealed putatively annotated metabolites and pathway mapping indicated their enrichment in metabolic pathways, biosynthesis of secondary metabolites, ubiquinone and terpenoid-quinones, brassinosteroids, steroids, terpenoids, phenylpropanoids, carotenoids, oxy/sphingolipids and metabolism of biotin and porphyrin. PCA, multivariate PLS-DA and OPLS-DA analysis showed sample discrimination. Significantly up regulated 481 and down regulated 548 metabolite features were identified based on the fold change (threshold ≥ 2.0). OPLS-DA model based on variable importance in projection (VIP scores) and FC threshold (> 2.0) revealed 41 up regulated discriminant metabolite features annotated as sphingosine, fecosterol, melatonin, serotonin, glucose 6-phosphate, zeatin, dihydrozeatin and zeatin-β-D-glucoside. Similarly, 23 down regulated discriminant metabolites included histidinol, 4-aminobutyraldehyde, propanoate, tyramine and linalool. Melatonin and serotonin in the leaves were the two indoleamines being reported for the first time in tomato in response to the early blight pathogen. Receiver operating characteristic (ROC)-based biomarker analysis identified apigenin-7-glucoside, uridine, adenosyl-homocysteine, cGMP, tyrosine, pantothenic acid, riboflavin (as up regulated) and adenosine, homocyctine and azmaline (as down regulated) biomarkers. These results could aid in the development of metabolite-quantitative trait loci (mQTL). Furthermore, stress-induced biosynthetic pathways may be the potential targets for modifications through breeding programs or genetic engineering for improving crop performance in the fields.

Untargeted Phytochemical Profiling, Antioxidant, and Antimicrobial Activities of a Tunisian Capsicum annuum Cultivar

Peppers are among the spices possessing a wide plethora of biological properties due to their excellent supply of health-related metabolites. Capsicum annuum L. (Solanaceae) is cultivated throughout Tunisia, and there is a shortage of information on the identification of the secondary metabolites in the seeds of this species as well as on their biological activities. In the present work, we intended to undertake a chemical characterization of the bioactive compounds from the hydro-methanolic seed extract of C. annuum as well as an evaluation of its broad spectrum of antimicrobial and antioxidant activities. The chemical profile was evaluated by RP-HPLC-DAD-QTOF-MS/MS, whereas the total phenol and flavonoid content, antioxidant, and antimicrobial activities were determined in in vitro assays. In this work, 45 compounds belonging to various phytochemical classes, such as organic acids (2), phenolic compounds (4 phenolic acids and 5 flavonoids), capsaicinoids (3), capsianosides (5), fatty acids (13), amino acids (1), sphingolipids (10), and steroids (2) were identified in the hydro-methanolic seed extract of C. annuum. The phenolic and flavonoid content (193.7 mg GAE/g DW and 25.1 mg QE/g DW, respectively) of the C. annuum extract correlated with the high antiradical activity (IC50 = 45.0 µg/mL), reducing power (EC50 = 61.3 µg/mL) and chelating power (IC50 = 79.0 µg/mL) activities. The hydro-methanolic seed extract showed an important antimicrobial activity against seven bacterial and four fungal strains. In fact, the inhibition zones (IZs) for bacteria ranged from 9.00 ± 1.00 mm to 12.00 ± 0.00 mm; for fungi, the IZs ranged from 12.66 ± 0.57 mm to 13.66 ± 0.57 mm. The minimal inhibition concentration and minimal bactericidal concentration values showed that the extract was more effective against fungi than bacteria.

An R-R-type MYB transcription factor promotes non-climacteric pepper fruit carotenoid pigment biosynthesis

Carotenoids are major accessory pigments in the chloroplast, and they also act as phytohormones and volatile compound precursors to influence plant development and confer characteristic colours, affecting both the aesthetic and nutritional value of fruits. Carotenoid pigmentation in ripening fruits is highly dependent on developmental trajectories. Transcription factors incorporate developmental and phytohormone signalling to regulate the biosynthesis process. By contrast to the well-established pathways regulating ripening-related carotenoid biosynthesis in climacteric fruit, carotenoid regulation in non-climacteric fruit is poorly understood. Capsanthin is the primary carotenoid of non-climacteric pepper (Capsicum) fruit; its biosynthesis is tightly associated with fruit ripening, and it confers red pigmentation to the ripening fruit. In the present study, using a coexpression analysis, we identified an R-R-type MYB transcription factor, DIVARICATA1, and demonstrated its role in capsanthin biosynthesis. DIVARICATA1 encodes a nucleus-localised protein that functions primarily as a transcriptional activator. Functional analyses showed that DIVARICATA1 positively regulates carotenoid biosynthetic gene (CBG) transcript levels and capsanthin levels by directly binding to and activating CBG promoter transcription. Furthermore, an association analysis revealed a significant positive association between DIVARICATA1 transcription level and capsanthin content. ABA promotes capsanthin biosynthesis in a DIVARICATA1-dependent manner. Comparative transcriptomic analysis of DIVARICATA1 in Solanaceae plants showed that its function likely differs among species. Moreover, the pepper DIVARICATA1 gene could be regulated by the ripening regulator MADS-RIN. The present study illustrates the transcriptional regulation of capsanthin biosynthesis and offers a target for breeding peppers with high red colour intensity.

Metabolic Variations among Three New Tea Varieties Cultivated in Shandong, China

Cultivar identification is a necessary step in tea breeding programs. Rapid identification methods would greatly improve these breeding processes. To preliminarily identify the three new Lucha tea varieties (LC6, LC7, and LC17) cultivated in Shandong, we measured their main agronomic characters and biochemical components. Then, we analyzed the metabolic profiles of these tea varieties and Fuding Dabaicha (FD) using a UPLC-ESI-MS/MS system. Their biochemical components indicated that the Lucha varieties had excellent varietal characteristics, with higher amino acid contents. Furthermore, secondary metabolism changed a lot in the Lucha tea varieties compared with that in the FD, with their accumulations of flavonoids and phenolic acids showing significant differences. These differential flavonoids were dominated by flavones and flavanone, flavonols, flavonoid carbonosides, and flavanols monomer. Flavanols especially, including epicatechin glucoside, epicatechin-3-(3″-O-methyl)gallate, epigallocatechin-3-O-(3,5-O-dimethyl)gallate, and epitheaflavic acid-3-O-Gallate, showed higher levels in the Lucha varieties. The phenolic acids containing caffeoyl groups showed higher levels in the Lucha varieties than those in the FD, while those containing galloyl groups showed a reverse pattern. Nitrogen metabolism, including amino acids, also showed obvious differences between the Lucha varieties and FD. The differential amino acids were mainly higher in the Lucha varieties, including 5-L-glutamyl-L-amino acid, N-monomethyl-L-arginine, and N-α-acetyl-L-ornithine. By using these approaches, we found that LC6, LC7, and LC17 were excellent varieties with a high yield and high quality for making green teas in Shandong.

Widely Targeted Metabolomics Reveals Metabolite Diversity in Jalapeño and Serrano Chile Peppers (Capsicum annuum L.)

Chile peppers (Capsicum annuum L.) are good sources of vitamins and minerals that can be included in the diet to mitigate nutritional deficiencies. Metabolomics examines the metabolites involved in biological pathways to understand the genes related to complex phenotypes such as the nutritional quality traits. The current study surveys the different metabolites present in jalapeño ('NuMex Pumpkin Spice') and serrano ('NuMex LotaLutein') type chile peppers grown in New Mexico using a widely targeted metabolomics approach, with the 'NuMex LotaLutein' as control. A total of 1088 different metabolites were detected, where 345 metabolites were differentially expressed; 203 (59%) were downregulated and 142 (41%) were upregulated (i.e., relative metabolite content is higher in 'NuMex Pumpkin Spice'). The upregulated metabolites comprised mostly of phenolic acids (42), flavonoids (22), and organic acids (13). Analyses of principal component (PC) and orthogonal partial least squares demonstrated clustering based on cultivars, where at least 60% of variation was attributed to the first two PCs. Pathway annotation identified 89 metabolites which are involved in metabolic pathways and the biosynthesis of secondary metabolites. Altogether, metabolomics provided insights into the different metabolites present which can be targeted for breeding and selection towards the improvement of nutritional quality traits in Capsicum.