Integrated Analysis of Transcriptome and Metabolome Reveal the Enhancement of Methyl Dihydrojasmonate on Physiological Indicators and Polyphyllins Biosynthesis in Paris polyphylla var. yunnanensis

Jasmonic acids, their effects on plant resistance and metabolites, have been extensively researched. However, methyl dihydrojasmonate (MDJ), a cost-effective and safe substitute for jasmonic acids, lacks sufficient research. This study presents a comprehensive analysis the impact of MDJ on Paris polyphylla var. yunnanensis. The present study aimed to enhance the accumulation of steroidal saponins (polyphyllin I, II, III, D, V, VI, VII, H) in Paris polyphylla var. yunnanensis which is a medicinal plant that contains medicinal steroidal saponins. To achieve this, different concentrations of MDJ were applied to Paris polyphylla var. yunnanensis. The study examined the impact of MDJ on physiology and polyphyllins. The optimal treatment concentration was identified, and the effects of MDJ on physiological metabolism and the expression pattern of related genes were explored. The results indicated that MDJ treatment significantly increased the levels of photosynthetic pigments, antioxidant enzymes, osmoregulators peaked at M2. Moreover, MDJ enhanced the accumulation of polyphyllins in both the leaves and rhizomes peaked at M2, particularly the sum of four polyphyllins (polyphyllin I, II, VI, VII) stated in the Chinese Pharmacopoeia, which increased by 45.65% following treatment. Based on transcriptome analysis, we revealed the polyphyllins-related genes by WGCNA. Furthermore, the majority of genes related to steroidal saponins were up-regulated following MDJ treatment. In the future, we recommend treating Paris polyphylla var. yunnanensis with suitable MDJ concentrations in production to efficiently enhance the yield of steroidal saponins.