Yuqi Sun

Konjac (Amorphophallus konjac K. Koch) has numerous health benefits, but traditional propagation is hindered by long growth periods and soil-borne diseases. This study developed a novel cell liquid culture system to directly produce micro-corms of konjac for large-scale production. The results demonstrated significant improvements in bud induction and rooting compared to solid culture. Under MS + 1.0 mg/L 6-BA + 0.5 mg/L NAA, the induced buds per culture vessel and final fresh weight were 24.87 ± 0.06 and 6.64 ± 0.12 g, respectively, 1.95 and 1.67 times higher than those in solid culture. Rooting experiments showed that 1/2 MS + 0.5 mg/L IBA + 1.0 mg/L NAA resulted in a root length of 25.23 ± 0.04 cm and 18.12 ± 0.01 roots per vessel. Using a 5 L bioreactor for micro-corm induction led to a 2.51-fold increase in fresh weight (52.67 ± 0.01 g) after 31 days, with glucomannan production reaching 0.48 g/g _{(fresh weight)}. The optimized culture system also significantly reduced the propagation time and increased the yield of healthy micro-corms. Bioreactor-based cultivation effectively enhances konjac induction efficiency and shortens breeding time, making it a promising approach for commercial production of konjac micro-corms and potentially improving the economic viability of konjac farming.

Dihydrochalcones (DHCs) constitute a specific class of flavonoids widely known for their various health-related advantages. Melatonin (MLT) has received attention worldwide as a master regulator in plants, but its roles in DHC accumulation remain unclear. Herein, the elicitation impacts of MLT on DHC biosynthesis were examined in Lithocarpus litseifolius, a valuable medicinal plant famous for its sweet flavor and anti-diabetes effect. Compared to the control, the foliar application of MLT significantly increased total flavonoid and DHC (phlorizin, trilobatin, and phloretin) levels in L. litseifolius leaves, especially when 100 μM MLT was utilized for 14 days. Moreover, antioxidant enzyme activities were boosted after MLT treatments, resulting in a decrease in the levels of intracellular reactive oxygen species. Remarkably, MLT triggered the biosynthesis of numerous phytohormones linked to secondary metabolism (salicylic acid, methyl jasmonic acid (MeJA), and ethylene), while reducing free JA contents in L. litseifolius. Additionally, the flavonoid biosynthetic enzyme activities were enhanced by the MLT in leaves. Multiple differentially expressed genes (DEGs) in RNA-seq might play a crucial role in MLT-elicited pathways, particularly those associated with the antioxidant system (SOD, CAT, and POD), transcription factor regulation (MYBs and bHLHs), and DHC metabolism (4CL, C4H, UGT71K1, and UGT88A1). As a result, MLT enhanced DHC accumulation in L. litseifolius leaves, primarily by modulating the antioxidant activity and co-regulating the physiological, hormonal, and transcriptional pathways of DHC metabolism.