Physiological and Transcriptomic Analyses of Effects of Exogenous MeJA on Seed germination of Hemp (Cannabis sativa L.) under Drought Stress

Water deficit inhibits hemp (Cannabis sativa L.) seed germination and its seedling growth. Application of exogenous methyl jasmonate (MeJA) can improve seed germination of hemp under drought condition, but little is known regarding its mechanism of MeJA-mediated drought tolerance in hemp. In this study, we conducted physiological and transcriptomic analysis to explore the effect of seeds soaking with MeJA on hemp seed germination at different stages under drought stress simulated with polyethylene glycol (PEG). The physiological results showed that PEG treatment inhibited the activity of peroxidase (POD) and exogenous MeJA application could promote POD activity under drought stress. Furthermore, compared with the control, exogenous MeJA maintained a higher level of proline content, which mitigated malondialdehyde (MDA) accumulation and reduced drought-induced damage. Comprehensive transcriptome analysis revealed that, under PEG treatment, 4,593 DEGs were annotated across the different time groups, whereas under MeJA + PEG treatment, 3,288 DEGs were annotated. Moreover, drought stress caused the down-regulated expression of a large number of genes, and MeJA treatment changed the expression of these related genes. A co-expression network was constructed by a weighted gene co-expression network analysis (WGCNA) and 17 candidate hub genes involved in drought tolerance were identified.