Comparative Analysis of Root Transcriptome Profiles of Sesame (Sesamum indicum L.) in Response to Osmotic Stress

Sesame (Sesamum indicum L) is a high-value oilseed cash crop grown across different geographies. Although sesame is traditionally considered drought-tolerant, early seedling and vegetative stage plants are sensitive to drought, causing substantial yield losses. Roots are the sensors of water deficit and hence are determinants of drought stress-induced responses. Limited information is available about the molecular responses induced in sesame roots during osmotic stress. We performed RNA-sequencing to understand transcriptional changes in the roots of drought-tolerant (TEX-1) and drought-sensitive (VEN-1) sesame genotypes using Polyethylene glycol (PEG)-induced osmotic stress. The photosynthetic measurements and proline accumulation confirmed contrasting drought stress reactions between the two genotypes. A total of 1251 and 541 unique genes were differentially expressed in PEG-treated and untreated roots of TEX-1 and VEN-1 roots, respectively. Gene ontology (GO) function enrichment analysis revealed that the differentially expressed genes related to catalytic activity, ion binding, transferase activity, and cation binding activities were over-represented. Transcription-factor enrichment analysis showed that multiple members of WRKY, bZIP, MYB, and NAC families were over-represented in the roots of drought-tolerant genotype during osmatic stress. The study identified several genes involved in the primary metabolism, phenylpropanoid, and hormonal pathways induced in the roots of drought-tolerant genotype. The study provided a comparative transcriptome resource for understanding molecular responses underlying osmotic stress and identified target genes for enhancing abiotic stress tolerance in sesame.