Transcript expression level analysis of phytoene synthase and phytoene desaturase associated with ß-carotene content in selected Kenyan Bitter melon.

BACKGROUND: Bitter melon (Momordica charantia L.) is a widely cultivated food and medicinal plant native to the world's subtropics and tropics. Constraints affecting cultivation of Bitter melon affect productivity of ß-carotene. Knowing the mechanism that controls the transcription of the ß-carotene biosynthesis genes in Bitter melon will be of great value in improving the yield of this important metabolite. METHODS AND RESULTS: The expressions of ß-carotene biosynthetic genes such as Phytoene Desaturase (PDS) and Phytoene Synthase (PSY) were evaluated in Bitter melon accessions 'GBK027049', 'NS1026', 'Mahy-ventura', '453B' and 'Sibuka532'. Transcript expression level analysis of PSY and PDS, and amount of ß-carotene in leaf, stem, and fruit, were determined using quantitative polymerase chain reaction and high-performance liquid chromatography (HPLC). Root transcript expression was used as a negative control for determining relative fold change in other tissues. Expression of PSY in fruit (6 to 27-fold compared to the control) was higher than in the other organs for all accessions. This was also the case of PDS expression (10 to 29-fold compared to the control). Leaves had the highest ß-carotene concentration (17.92-45.35 µg∙g-1); there was no difference between stems (5.67-12.75 µg∙g-1) and fruit (6.18-12.53 µg∙g-1). The highest ß-carotene content was in accessions 'GBK027049' (12.53-45.35 µg∙g-1) and '453B' (6.18-32.09 µg∙g-1). The PSY and PDS expressions were positively correlated with amount of ß-carotene in leaves, stems, and fruits. CONCLUSION: Bitter melon leaves, especially those of 'GBK027049' and '453B' accessions, are an alternative to alleviate the ß-carotene deficiencies in the world and especially in Africa.

Transcriptome analysis of five different tissues of bitter gourd (Momordica charantia L.) fruit identifies full-length genes involved in seed oil biosynthesis.

The bitter gourd seed oil, rich in conjugated fatty acids, has therapeutic value to treat cancer, obesity, and aging. It also has an industrial application as a drying agent. Despite its significance, genomics studies are limited, and the genes for seed oil biosynthesis are not fully understood. In this study, we assembled the fruit transcriptome of bitter gourd using 254.5 million reads (Phred score > 30) from the green rind, white rind, pulp, immature seeds, and mature seeds. It consisted of 125,566 transcripts with N50 value 2,751 bp, mean length 960 bp, and 84% completeness. Transcript assembly was validated by RT-PCR and qRT-PCR analysis of a few selected transcripts. The transcripts were annotated against the NCBI non-redundant database using the BLASTX tool (E-value < 1E-05). In gene ontology terms, 99,443, 86,681, and 82,954 transcripts were classified under biological process, molecular function, and cellular component. From the fruit transcriptome, we identified 26, 3, and 10 full-length genes coding for all the enzymes required for synthesizing fatty acids, conjugated fatty acids, and triacylglycerol. The transcriptome, transcripts with tissue-specific expression patterns, and the full-length identified from this study will serve as an important genomics resource for this important medicinal plant.

Long-read bitter gourd (Momordica charantia) genome and the genomic architecture of nonclassic domestication.

The genetic architecture of quantitative traits is determined by both Mendelian and polygenic factors, yet classic examples of plant domestication focused on selective sweep of newly mutated Mendelian genes. Here we report the chromosome-level genome assembly and the genomic investigation of a nonclassic domestication example, bitter gourd (Momordica charantia), an important Asian vegetable and medicinal plant of the family Cucurbitaceae. Population resequencing revealed the divergence between wild and South Asian cultivars about 6,000 y ago, followed by the separation of the Southeast Asian cultivars about 800 y ago, with the latter exhibiting more extreme trait divergence from wild progenitors and stronger signs of selection on fruit traits. Unlike some crops where the largest phenotypic changes and traces of selection happened between wild and cultivar groups, in bitter gourd large differences exist between two regional cultivar groups, likely reflecting the distinct consumer preferences in different countries. Despite breeding efforts toward increasing female flower proportion, a gynoecy locus exhibits complex patterns of balanced polymorphism among haplogroups, with potential signs of selective sweep within haplogroups likely reflecting artificial selection and introgression from cultivars back to wild accessions. Our study highlights the importance to investigate such nonclassic example of domestication showing signs of balancing selection and polygenic trait architecture in addition to classic selective sweep in Mendelian factors.

Accumulation of Charantin and Expression of Triterpenoid Biosynthesis Genes in Bitter Melon (Momordica charantia).

Charantin, a natural cucurbitane type triterpenoid, has been reported to have beneficial pharmacological functions such as anticancer, antidiabetic, and antibacterial activities. However, accumulation of charantin in bitter melon has been little studied. Here, we performed a transcriptome analysis to identify genes involved in the triterpenoid biosynthesis pathway in bitter melon seedlings. A total of 88,703 transcripts with an average length of 898 bp were identified in bitter melon seedlings. On the basis of a functional annotation, we identified 15 candidate genes encoding enzymes related to triterpenoid biosynthesis and analyzed their expression in different organs of mature plants. Most genes were highly expressed in flowers and/or fruit from the ripening stages. An HPLC analysis confirmed that the accumulation of charantin was highest in fruits from the ripening stage, followed by male flowers. The accumulation patterns of charantin coincide with the expression pattern of McSE and McCAS1, indicating that these genes play important roles in charantin biosynthesis in bitter melon. We also investigated optimum light conditions for enhancing charantin biosynthesis in bitter melon and found that red light was the most effective wavelength.

Draft genome sequence of bitter gourd (Momordica charantia), a vegetable and medicinal plant in tropical and subtropical regions.

Bitter gourd (Momordica charantia) is an important vegetable and medicinal plant in tropical and subtropical regions globally. In this study, the draft genome sequence of a monoecious bitter gourd inbred line, OHB3-1, was analyzed. Through Illumina sequencing and de novo assembly, scaffolds of 285.5 Mb in length were generated, corresponding to ∼84% of the estimated genome size of bitter gourd (339 Mb). In this draft genome sequence, 45,859 protein-coding gene loci were identified, and transposable elements accounted for 15.3% of the whole genome. According to synteny mapping and phylogenetic analysis of conserved genes, bitter gourd was more related to watermelon (Citrullus lanatus) than to cucumber (Cucumis sativus) or melon (C. melo). Using RAD-seq analysis, 1507 marker loci were genotyped in an F2 progeny of two bitter gourd lines, resulting in an improved linkage map, comprising 11 linkage groups. By anchoring RAD tag markers, 255 scaffolds were assigned to the linkage map. Comparative analysis of genome sequences and predicted genes determined that putative trypsin-inhibitor and ribosome-inactivating genes were distinctive in the bitter gourd genome. These genes could characterize the bitter gourd as a medicinal plant.

De Novo Assembly of Bitter Gourd Transcriptomes: Gene Expression and Sequence Variations in Gynoecious and Monoecious Lines.

Bitter gourd (Momordica charantia L.) is a nutritious vegetable crop of Asian origin, used as a medicinal herb in Indian and Chinese traditional medicine. Molecular breeding in bitter gourd is in its infancy, due to limited molecular resources, particularly on functional markers for traits such as gynoecy. We performed de novo transcriptome sequencing of bitter gourd using Illumina next-generation sequencer, from root, flower buds, stem and leaf samples of gynoecious line (Gy323) and a monoecious line (DRAR1). A total of 65,540 transcripts for Gy323 and 61,490 for DRAR1 were obtained. Comparisons revealed SNP and SSR variations between these lines and, identification of gene classes. Based on available transcripts we identified 80 WRKY transcription factors, several reported in responses to biotic and abiotic stresses; 56 ARF genes which play a pivotal role in auxin-regulated gene expression and development. The data presented will be useful in both functions studies and breeding programs in bitter gourd.

Molecular cloning and characterization of cDNAs encoding carotenoid cleavage dioxygenase in bitter melon (Momordica charantia).

Carotenoid cleavage dioxygenases (CCDs) are a family of enzymes that catalyze the oxidative cleavage of carotenoids at various chain positions to form a broad spectrum of apocarotenoids, including aromatic substances, pigments and phytohormones. Using the rapid amplification of cDNA ends (RACE) PCR method, we isolated three cDNA-encoding CCDs (McCCD1, McCCD4, and McNCED) from Momordica charantia. Amino acid sequence alignments showed that they share high sequence identity with other orthologous genes. Quantitative real-time RT PCR (reverse transcriptase PCR) analysis revealed that the expression of McCCD1 and McCCD4 was highest in flowers, and lowest in roots and old leaves (O-leaves). During fruit maturation, the two genes displayed differential expression, with McCCD1 peaking at mid-stage maturation while McCCD4 showed the lowest expression at that stage. The mRNA expression level of McNCED, a key enzyme involved in abscisic acid (ABA) biosynthesis, was high during fruit maturation and further increased at the beginning of seed germination. When first-leaf stage plants of M. charantia were exposed to dehydration stress, McNCED mRNA expression was induced primarily in the leaves and, to a lesser extend, in roots and stems. McNCED expression was also induced by high temperature and salinity, while treatment with exogenous ABA led to a decrease. These results should be helpful in determining the substrates and cleavage sites catalyzed by CCD genes in M. charantia, and also in defining the roles of CCDs in growth and development, and in the plant's response to environmental stress.

Riboflavin accumulation and characterization of cDNAs encoding lumazine synthase and riboflavin synthase in bitter melon (Momordica charantia).

Riboflavin (vitamin B2) is the universal precursor of the coenzymes flavin mononucleotide and flavin adenine dinucleotide--cofactors that are essential for the activity of a wide variety of metabolic enzymes in animals, plants, and microbes. Using the RACE PCR approach, cDNAs encoding lumazine synthase (McLS) and riboflavin synthase (McRS), which catalyze the last two steps in the riboflavin biosynthetic pathway, were cloned from bitter melon (Momordica charantia), a popular vegetable crop in Asia. Amino acid sequence alignments indicated that McLS and McRS share high sequence identity with other orthologous genes and carry an N-terminal extension, which is reported to be a plastid-targeting sequence. Organ expression analysis using quantitative real-time RT PCR showed that McLS and McRS were constitutively expressed in M. charantia, with the strongest expression levels observed during the last stage of fruit ripening (stage 6). This correlated with the highest level of riboflavin content, which was detected during ripening stage 6 by HPLC analysis. McLS and McRS were highly expressed in the young leaves and flowers, whereas roots exhibited the highest accumulation of riboflavin. The cloning and characterization of McLS and McRS from M. charantia may aid the metabolic engineering of vitamin B2 in crops.

Mining the bitter melon (momordica charantia l.) seed transcriptome by 454 analysis of non-normalized and normalized cDNA populations for conjugated fatty acid metabolism-related genes.

BACKGROUND: Seeds of Momordica charantia (bitter melon) produce high levels of eleostearic acid, an unusual conjugated fatty acid with industrial value. Deep sequencing of non-normalized and normalized cDNAs from developing bitter melon seeds was conducted to uncover key genes required for biotechnological transfer of conjugated fatty acid production to existing oilseed crops. It is expected that these studies will also provide basic information regarding the metabolism of other high-value novel fatty acids. RESULTS: Deep sequencing using 454 technology with non-normalized and normalized cDNA libraries prepared from bitter melon seeds at 18 DAP resulted in the identification of transcripts for the vast majority of known genes involved in fatty acid and triacylglycerol biosynthesis. The non-normalized library provided a transcriptome profile of the early stage in seed development that highlighted the abundance of transcripts for genes encoding seed storage proteins as well as for a number of genes for lipid metabolism-associated polypeptides, including Δ12 oleic acid desaturases and fatty acid conjugases, class 3 lipases, acyl-carrier protein, and acyl-CoA binding protein. Normalization of cDNA by use of a duplex-specific nuclease method not only increased the overall discovery of genes from developing bitter melon seeds, but also resulted in the identification of 345 contigs with homology to 189 known lipid genes in Arabidopsis. These included candidate genes for eleostearic acid metabolism such as diacylglycerol acyltransferase 1 and 2, and a phospholipid:diacylglycerol acyltransferase 1-related enzyme. Transcripts were also identified for a novel FAD2 gene encoding a functional Δ12 oleic acid desaturase with potential implications for eleostearic acid biosynthesis. CONCLUSIONS: 454 deep sequencing, particularly with normalized cDNA populations, was an effective method for mining of genes associated with eleostearic acid metabolism in developing bitter melon seeds. The transcriptomic data presented provide a resource for the study of novel fatty acid metabolism and for the biotechnological production of conjugated fatty acids and possibly other novel fatty acids in established oilseed crops.

Antioxidant properties of Momordica Charantia (bitter gourd) seeds on Streptozotocin induced diabetic rats.

The aim of the present study is to investigate the antioxidant activities of the aqueous extract of seeds of two varieties, namely a country and hybrid variety of Momordica charantia (MCSEt1 and MCSEt2) respectively in streptozotocin induced diabetic rats. Oral administration of both the seed extracts at a concentration of 150 mg/kg b.w for 30 days showed a significant decrease in fasting blood glucose, hepatic and renal thiobarbituric acid reactive substances and hydroperoxides. The treatment also resulted in a significant increase in reduced glutathione, superoxide dismutase, catalase, glutathione peroxidase and glutathione-s-transferase in the liver and kidney of diabetic rats. The results clearly suggest that seeds of Momordica charantia treated group may effectively normalize the impaired antioxidant status in streptozotocin induced-diabetes than the glibenclamide treated groups. The extract exerted rapid protective effects against lipid peroxidation by scavenging of free radicals there by reducing the risk of diabetic complications. The effect was more pronounced in MCSEt1 compared to MCSEt2.