Transcriptomic responses of barley (Hordeum vulgare L.) to drought and salinity

Abstract

Drought and salinity are the main factors limiting plant growth and productivity. With the effects of global warming, severe drought episodes are expected to be widespread, which will certainly lead to decrease in crop production. Therefore, understanding plants’ response to drought and salinity stresses is more urgent than ever to reveal molecular mechanisms behind the natural tolerance which, then, can be used in the generation of stress-tolerant crop species. Barley stands out as the most salinity and drought-tolerant crop in Poaceae family with its wide range of wild genotypes. Due to its higher tolerance to abiotic and biotic stresses among other crops, it was studied to understand the mechanisms behind the natural tolerance via generation of various genetic resources and databases created by extensive sequence data, microarray studies, next-generation sequencing (NGS), and genetic maps. Large-scale transcriptomic analyses in barley showed that ROS-scavenging enzymes, transcription factors, LEA group proteins, and enzymes coding for osmoprotectants are the prominent groups of genes differentially expressed under salinity and drought stresses. Quantitative real-time PCR was efficiently used to measure transcript levels of stress-related genes under high salt or limited water conditions, allowing the prediction of functional characteristics of these genes according to their expression patterns. Small-scale expression studies also revealed the importance of cell and tissue type expression and mode of the stress treatment. However, although there are numerous candidate barley genes that can be used to develop transgenic crops with higher tolerance to salinity and drought, there are only limited isolation and cloning studies with these genes. We highly recommend more detailed studies on this naturally tolerant crop to be able to generate more drought or salt tolerance species via genetic transformation.