Comprehensive physiological and transcriptomic insights into drought stress responses in faba bean (Vicia Faba L.)

Drought is a major limiting constraint to faba bean production worldwide, including Tunisia. However, molecular mechanisms underlying faba bean responses to drought stress are not well understood. In this context, RNA-seq was applied to investigate drought-related genes and construct a network of faba bean (Vicia faba L.) drought stress response and tolerance. Assembly of the transcriptome generated 26,728 differentially expressed genes (DEGs). Of these, 13,920 were up-regulated and 12,808 down-regulated in faba bean drought-stressed leaves. Moreover, a total of 2130 transcription factors involved in major metabolic pathways including abscisic acid (ABA)-dependent and -independent signaling pathway were identified. Gene Ontology (GO), Eukaryotic Orthologous Groups (KOG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses revealed that these DEGs were involved in several important processes including photosynthesis, flavonoid biosynthesis, response to stimulus and abiotic stress, reactive oxygen species (ROS) scavengers, signal transduction, biosynthesis of secondary metabolites and transporters, suggesting the involvement of these important pathways in faba bean response to water deficit. Various stress proteins such as late embryogenesis abundant proteins (LEA), dehydrins (DHNs) and heat shock proteins (HSPs) have been identified and their expression was robustly upregulated in drought-stressed leaves, indicating their key contribution to drought response and adaptation by conferring protection and providing stability to faba bean plant cellular processes under water deficit. The reliability of the RNA-seq results was confirmed by the analysis of 10 randomly selected genes using qRT-PCR. Taken together, these findings help advancing our knowledge and can guide breeding programs aimed at improving the tolerance of faba bean to drought stress.