Transcriptomic Analysis of Methyl Jasmonate Treatment Reveals Gene Networks Involved in Drought Tolerance at the Early Developmental Stage in Pearl Millet (Pennisetum Glaucum L. Br)

Water deficit stress at the early stage of development is one of the main factors limiting pearl millet production. A practice to cope with would be to apply hormones to stimulate plant growth and development. Exogenous methyl jasmonate (MeJA) can improve drought tolerance by modulating key pathways, therefore, we assumed that can occur in pearl millet during the early stage of development. To decipher the molecular mechanisms controlling these pathways, RNAseq was conducted in two pearl millet genotypes, drought-sensitive SosatC88 and drought-tolerant Souna3, in response to 200 µM of MeJA. Transcriptomic analysis between the MeJA-treated and non-treated plants revealed 3270 differentially expressed genes (DEGs) in SosatC88 and 127 DEGs in Souna3. Gene ontology (GO) classification assigned most regulated DEGs in SosatC88 to heme binding, oxidation-reduction process, response to oxidative stress and membrane, and in Souna3 to terpene synthase activity, lyase activity, magnesium ion binding, and thylakoid. The Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis reveals that DEGs in SosatC88 are related to the oxidation-reduction process, the biosynthesis of other secondary metabolites, the signal transduction, and the metabolism of terpenoids, while in Souna3, DEGs are related to the metabolism of terpenoids and the energy metabolism. Two genes encoding a diterpenoid biosynthesis-related and a Glutathione S transferase T3 were contra-regulated between SosatC88 and Souna3. Additionally, five random genes differentially expressed by RNAseq were validated using qPCR. These insights into the molecular mechanisms of pearl millet genotype tolerance at the early stage of development contribute to the understanding of the role of hormones in adaptation to drought-prone environments.