Transcriptome Analysis for Gaining Insight into Gingerol Biosynthesis and MAPK-Dependent Hormonal Signaling Pathway Involved in Resistance Mechanism in Fusarium Wilt Tolerant Ginger (Zingiber officinale Rosc.) Produced Through In Vitro Mutagenesis and Selection

Ginger (Zingiber officinale Rosc.) is the most widely used medicinal herb of the ancient "Ayurveda" and "Unani" system of medicine due to bioactive compounds present in its rhizomes, i.e., volatile oils (terpenoids), diarylheptanoids (curcuminoids), and gingerols (phenols), which serve as an important panacea for treating arthritis, heart diseases, cancer, diarrhea, and respiratory disorders. It is a vegetatively propagated crop through underground rhizomes and its production is hampered by various soil-borne pathogens which predominantly include Fusarium oxysporum f.sp. zingiberi. During the preceding research, the technique of in vitro mutagenesis and selection was employed in ginger cv. Himgiri for the development of Fusarium tolerant lines, resulting in mutant Himgiri-17.5, which displayed improved accumulation of gingerol and demonstrated enhanced tolerance to Fusarium wilt. The present study reveals the first-ever transcriptome data of in vitro-raised Himgiri-17.5 to unravel the role of gingerol biosynthesis and MAPK-dependent hormonal signaling pathways in imparting tolerance to Fusarium wilt as compared to conventionally propagated Himgiri. Through transcriptome analysis, a total of 13.84 GB data was generated encoding 57,939 genes, out of which 3745 were differentially expressed genes (DEGs) in both the samples with 351 upregulated and 3394 downregulated. The expression patterns of genes in Himgiri-17.5 linked to antioxidant activity and MAPK-dependent hormonal signaling exhibited notable upregulation suggesting their possible participation in mediating plant defense response. Additionally, the investigation provided insights into volatile oil, diarylheptanoids, and gingerol biosynthetic pathway in ginger governed by crucial regulatory genes, namely DCS, CURS2, and ClPKS10. The examination also revealed the presence of 165 upregulated transcription factors primarily belonging to the ERF, bHLH, MYB, NAC, and bZIP families which exhibited a strong correlation with the biosynthesis of gingerol and MAPK-mediated hormonal signaling pathway, contributing to stress tolerance. The discovery of these DEGs related to antioxidant activity, MAPK-mediated hormonal signaling, and the biosynthetic pathway of gingerol holds a promise for the development of improved varieties of ginger through molecular approaches.