Comparative Network Analysis under ABA and Chitosan Treatments: Unveiling Key Transcriptional Regulators of Valerenic Acid Biosynthesis in Valerian Hairy Roots

Valerenic acid is a sesquiterpene compound found in Valeriana officinalis (valerian) and has gained attention for its potential as a natural remedy for anxiety, insomnia, and stress-related disorders due to its calming and sedative properties. The low compound content and slow plant growth have limited its production, so a biotechnological approach such as hairy root culture is needed to scale up valerenic acid without using natural resources. This study aims to elucidate the structural and dynamic features of the gene and transcription factor network underlying valerenic acid production in the hairy root cultures of valerian under ABA and chitosan elicitation. ABA treatment induced significant changes in the expression of BHLH and ERBP transcription factors. Their relative expression levels peaked on the second day. Among the genes encoding terpene synthase enzymes, TPS5 shows the strongest induction. When induced with chitosan, the transcription factors BHLH and ERBP play a critical role in enhancing valerenic acid accumulation by upregulating the expression of HMGR, TPS2, and TPS5. In addition, WRKY, ERBP, and MYB transcription factors act as critical regulators in the activation of terpene synthases. Chitosan treatment leads to the highest valerenic acid level (0.68 mg/g DW) on day 2. In comparison, ABA triggers the highest valerenic acid level (0.65 mg/g DW) on day 4. Our results have significant implications for the development of efficient and sustainable strategies for the large-scale production of valerenic acid, a valuable compound widely used in the pharmaceutical industry.