Document Type : Research Paper
Authors
1
Dept. of Genetics and Plant Breeding, Imam Khomeini International University, Qazvin, I.R. Iran
2
Associate Professor, Department of Genetics & Plant Breeding, Imam Khomeini International University, Qazvin, Iran.
3
Dept. of Genetics and Plant Breeding, Faculty of Agriculture & Natural Resources, Imam Khomeini International University, Qazvin, I.R. Iran
10.22092/ijrfpbgr.2026.372298.1491
Abstract
Background and Objectives: Black nightshade (Solanum nigrum L.), a medicinal species belonging to the Solanaceae family, has attracted considerable attention because of its production of steroidal glycoalkaloids, particularly solasonine, which exhibits remarkable antitumor, anti-inflammatory, and antimicrobial activities. Solasonine glycosyltransferase (SGT1) catalyzes the final step of the solasonine biosynthetic pathway by transferring a glycosyl moiety to the steroidal aglycone solasodine. Despite the biological and pharmaceutical importance of solasonine, limited information is available regarding the SGT1 coding gene and its expression profile in S. nigrum. Therefore, this study aimed to isolate the full-length coding cDNA of the SGT1 gene and investigate its expression pattern in different plant tissues following methyl jasmonate treatment, a well-known elicitor and key regulator of plant secondary metabolism.
Materials and Methods: To evaluate the effect of methyl jasmonate on SGT1 gene expression, a completely randomized design with three replications was employed. Solanum nigrum seeds were grown under greenhouse conditions, and leaf, immature green fruit, and ripe fruit samples were collected one day after spraying reproductive-stage plants with 100 µM methyl jasmonate. Based on transcriptomic data retrieved from the NCBI database and sequence analysis using the BLASTn algorithm, a consensus sequence was generated, and gene-specific primers were designed to amplify the coding cDNA of SGT1. The amplified PCR product was purified, cloned into the pNovel T/A Lethal Vector, transformed into Escherichia coli DH5α competent cells, and subsequently sequenced. Relative gene expression was quantified using quantitative real-time PCR (qRT-PCR) with gene-specific primers, while the Elongation factor 1α gene served as the internal reference. Relative transcript abundance was calculated using the 2^−ΔΔCt method. Statistical analyses, including analysis of variance and Duncan’s multiple range test, were performed using MSTAT-C and Microsoft Excel software.
Results: A full-length coding cDNA of the SGT1 gene, comprising 1,479 base pairs, was successfully isolated and cloned from S. nigrum. Protein sequence analysis identified the highly conserved uridine diphosphate glycosyltransferase (UDPGT) signature motif together with the characteristic plant secondary product glycosyltransferase (PSPG) domain located at the C-terminal region. The conserved HCGTNS motif, recognized as a diagnostic sequence of SGT1 enzymes in the genus Solanum, was identified, while substitution of the conserved tryptophan residue with threonine represented a distinctive structural characteristic of S. nigrum SGT1. Phylogenetic analysis demonstrated that the SGT1 protein of S. nigrum clustered most closely with that of Solanum dulcamara, indicating a close evolutionary relationship between the two species. Gene expression analysis revealed significant effects of tissue type, methyl jasmonate treatment, and their interaction. Overall, methyl jasmonate significantly enhanced SGT1 transcript accumulation compared with untreated control plants. The highest expression level (8.76) was detected in methyl jasmonate-treated immature green fruits, representing a 3.7-fold increase relative to the corresponding control, whereas the lowest expression level was observed in ripe fruits. These findings indicate that methyl jasmonate effectively induces SGT1 expression in all examined tissues, although the magnitude of induction differs among tissues, demonstrating a clear tissue-specific transcriptional response.
Conclusion: The successful isolation and characterization of the SGT1 gene provides valuable insight into the molecular basis of solasonine biosynthesis in S. nigrum. Given the considerable pharmaceutical potential of solasonine, particularly its antitumor properties, the findings of this study provide a valuable foundation for future metabolic engineering and biotechnological strategies aimed at enhancing solasonine production in cell cultures and transgenic plants. Furthermore, elucidating the regulatory effect of methyl jasmonate on SGT1 expression contributes to a better understanding of secondary metabolite biosynthesis and may facilitate the development of effective approaches for improving the production of valuable bioactive compounds in S. nigrum.
Keywords
Main Subjects
)