Molecular insights into charantin and β-carotene biosynthesis in bitter gourd (Momordica charantia L.): Gene expression dynamics and metabolite profiling.

Bitter gourd is recognized for its anticancer and antidiabetic properties, largely attributed to charantin, and is also a rich source of carotenoids, including β-carotene. In this study, considerable variation was observed in both the accumulation and gene expression patterns associated with charantin and β-carotene biosynthesis across diverse genotypes. PVGy-201 exhibited the strongest gene expression profile, with the highest transcript levels for five key genes, including McIDI (∼16,493-fold), McPMK (∼694-fold), and McSE (∼466-fold), which corresponded with the maximum charantin content (38.53 µg/g FW). Similarly, DBGS-2 showed elevated expression of McHMGR1 (∼271-fold) and McMK (∼13-fold), supporting its high charantin accumulation (35.27 µg/g FW). The wild species Momordica balsamina demonstrated strong expression of McHMGR2 and McSE, consistent with charantin content of 29.36 µg/g FW. For β-carotene, DBGS-21-06 recorded peak expression of McPSY (∼17.2-fold), McZDS (∼4.9-fold), and McCHXB (∼2.8-fold), aligning with high carotenoid levels at both edible (18.46 µg/g FW) and ripening (52.31 µg/g FW) stages. Pusa Rasdar showed elevated expression of McZEP (∼6.9-fold) and McPDS (∼10.8-fold), correlating with maximum carotenoid content (19.49 µg/g FW at edible stage and 55.66 µg/g FW at ripening). DBGS-100-0 expressed McLCYE1 (∼2.9-fold) and McLCYE2 (∼3.1-fold), with high carotenoids (15.91 µg/g FW) at the edible stage. Collectively, PVGy-201 and DBGS-2 were identified as promising candidates for charantin enrichment, while DBGS-21-06 and Pusa Rasdar emerged as superior for β-carotene accumulation. These genotype-specific insights provide a molecular framework to support marker-assisted selection, transcriptome-based screening, and metabolic engineering for the development of nutritionally enhanced bitter gourd cultivars with stable metabolite profiles.