Adaptation Strategies of Halophytic Barley Hordeum marinum ssp. marinum to High Salinity and Osmotic Stress

Abstract

The adaptation strategies of halophytic seaside barley Hordeum marinum to high salinity and osmotic stress were investigated by nuclear magnetic resonance imaging, as well as ionomic, metabolomic, and transcriptomic approaches. When compared with cultivated barley, seaside barley exhibited a better plant growth rate, higher relative plant water content, lower osmotic pressure, and sustained photosynthetic activity under high salinity, but not under osmotic stress. As seaside barley is capable of controlling Na+ and Cl− concentrations in leaves at high salinity, the roots appear to play the central role in salinity adaptation, ensured by the development of thinner and likely lignified roots, as well as fine-tuning of membrane transport for effective management of restriction of ion entry and sequestration, accumulation of osmolytes, and minimization of energy costs. By contrast, more resources and energy are required to overcome the consequences of osmotic stress, particularly the severity of reactive oxygen species production and nutritional disbalance which affect plant growth. Our results have identified specific mechanisms for adaptation to salinity in seaside barley which differ from those activated in response to osmotic stress. Increased knowledge around salt tolerance in halophytic wild relatives will provide a basis for improved breeding of salt-tolerant crops.

The Halophyte Dehydrin Sequence Landscape

“…Interestingly, it seems that for some DHNs, there is preference for some architectures by stress. We investigated, for instance, the changes in expression under salt stress of different architectures in the leaves, shoots, and roots of three species ( Puccinellia tenuiflora Eutrema salsugenium, and Hordeum marinum ), according to the previously reported studies [ 50 , 51 , 52 ]. As shown in Figure 5 , YnSKn dehydrins are significantly more induced by salt stress than SKn in Puccinellia tenuiflora in leaves and roots with log2-fold changes reaching up to 5.63 and 3.44, respectively ( Figure 5 A).…”

“…Expression data were collected from the previous reports [ 50 , 51 , 52 ]. Using gene IDs available in these studies, we have identified the protein sequences of dehydrins in the Phytozome v13 database and determined their architectures by using MEME.…”

“…( B ) Relative gene expression of DHN architectures in Eutrema salsugenium leaves and root after 24 h of salt stress (NaCl 300 mM) [ 51 ]. ( C ) Relative gene expression of DHN architectures in Hordeum marinum shoots and roots after 5 days of salt stress (NaCl 300 mM) [ 52 ].…”

Higher activity of PSI compared to PSII accounts for the beneficial effect of silicon on barley (Hordeum vulgare L.) plants challenged with salinity

“…The osmotic stress is due to the loss of cellular water content, caused by Na + and Clions accumulation (ion toxicity). These ions are the main contributors to the cellular osmotic potential, and they have to be compartmentalized and sequestrated into vacuoles or endosomal compartments by ion exchangers and the H + pumps localized in the tonoplast or endosomal membranes (Isayenkov et al 2020). This subsequently limits nutrient uptake and photosynthetic assimilation by crops to increase productivity (Xue et al 2019).…”

Molecular Aspects of Plant Salinity Stress and Tolerance

“…They revealed that certain genes were found to express differentially in response to salinity, and these genes might code for transcription factors, or were proposed to be related to primary metabolism, endocytosis, hormonal pathways, and transporters. Isayenkov et al investigated strategies for adaptation to salinity in seaside barley, using nuclear magnetic resonance imaging associated with multi-omics approaches [ 2 ]. The authors proposed that seaside barley has developed specific mechanisms involving the capability to regulate concentrations of Na + and Cl − in leaves and morphological and physiological adaptations of roots when subjected to salinity stress.…”