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• NaCl stimulates the growth of salt-secreting Reaumuria soongorica. • NaCl assists R. soongorica to maintain leaf morphology structure under drought stress. • Salt secretion helps R. soongorica to keep the better growth under arid-salinity habitat. Reaumuria soongorica, a salt-secreting xerophytic shrub, is a dominant species in arid desert regions of northwest China. To investigate whether NaCl could stimulate the growth and alleviate drought stress in R. soongorica , the seedlings were treated with a range of different concentrations of 0–1.17 g kg−1 NaCl, and also were withheld water for drought stress under without or supplementary 0.59 g kg-1 NaCl. The results showed that 0.59 g kg-1 NaCl (moderate NaCl) significantly stimulated the growth of R. soongorica , and also effectively alleviated deleterious impacts of drought stress on its growth and leaf morphological structure. Further analysis showed that moderate NaCl significantly improved photosynthetic capacity and mitigated light suppression of drought stress on photosystem II in R. soongorica , concomitantly, decreased osmotic potential, enlarged turgor pressure as well as increased the relative water content in leaves under drought stress. Furthermore, moderate NaCl induced an obvious increase of Na+ accumulation in tissues of R. soongorica , which resulted in a significant increase of the contribution of Na+ to leaf osmotic potential from13 to 22% under drought stress. Additionally, moderate NaCl also promoted Na+ secretion via salt glands of leaf. These results suggest that the positive roles of NaCl on the growth and drought resistance of R. soongorica is due to the increase of Na+ accumulating in leaf tissues, facilitating plant to maintain higher photosynthetic activity and better water status in arid environment, simultaneously, salt secretion of salt glands protects plant from excess Na+ toxicity. [ABSTRACT FROM AUTHOR]

Abstract: Salinity and drought are two major abiotic factors limiting crop production. To generate the legume forage adapting to saline and arid soils, we had transformed alfalfa (Medicago sativa) with AVP1, a vacuolar H+-pyrophosphatase (H+-PPase) gene from Arabidopsis thaliana. In this paper, we report that overexpression of the AVP1 gene confers enhanced salt and drought tolerance to the transformed alfalfa. Transgenic alfalfa grows well in the presence of 200mM NaCl and also under a water-deprivation condition, while wild-type plants exhibit chlorosis and growth inhibition, even death. Compared with wild-type plants, transgenic plants accumulate more Na+, K+ and Ca2+ in leaves and roots. Moreover, the leaves of transgenic plants retain more water during drought stress than those of wild-type plants due to lower solute potential. Increased solute accumulation and water retention, and steady intracellular ion homeostasis might also confer other phenotypes of salt and drought tolerance in the transgenic plants, which include the higher photosynthesis capacity and the lesser cell membrane damage during salt or water-deficit stress. Furthermore, the increased potassium uptake and root activity in transgenic alfalfa may be the consequences of rhizosphere acidification resulting from expression of the AVP1. These results indicated that the expression of AVP1 confers enhanced salt and drought tolerance on alfalfa, a very important crop. This study provides a way for improving salt and drought tolerance in important legume forages. [Copyright &y& Elsevier]

Atriplex canescens is a C 4 shrub with excellent adaptation to saline and arid environments. Our previous study showed that the secretion of excessive Na+ into leaf salt bladders is a primary strategy in salt tolerance of A. canescens and external 100 mM NaCl can substantially stimulate its growth. To investigate whether NaCl could facilitate Atriplex canescens response to drought stress, five-week-old seedlings were subjected to drought stress (30% of field water capacity) in the presence or absence of additional 100 mM NaCl. The results showed that, under drought stress, the addition of NaCl could substantially improve the growth of A. canescens by increasing leaf relative water content, enhancing photosynthetic activity and inducing a significant declined leaf osmotic potential (Ψs). The addition of NaCl significantly increased Na+ concentration in leaf salt bladders and the Na+ contribution to leaf Ψs , while had no adverse effects on K+ accumulation in leaf laminae. Therefore, the large accumulation of Na+ in salt bladders for enhancing osmotic adjustment (OA) ability is a vital strategy in A. canescens responding to drought stress. In addition, the concentration of free proline, bataine and soluble sugars exhibited a significant increase in the presence of NaCl under drought stress, and the betaine contribution to leaf Ψs was significantly increased by additional NaCl compared with that under drought treatment alone, suggesting that compatible solutes are also involved in OA in addition to functioning as protectants to alleviate water deficit injury. • A. canescens could grow well in drought soils that contain certain salt. • Na+ secretion and K+ retention are vital strategies for A. canescens to cope with water deficit. • NaCl improves photosynthesis and hydration of A. canescens under drought stress. [ABSTRACT FROM AUTHOR]

Abstract: Sodium (Na+) has been found to play important roles in the adaptation of xerophytic species to drought conditions. The tonoplast Na+/H+ antiporter (NHX) proved to be involved in the compartmentalization of Na+ into vacuoles from the cytosol. In this study, a gene (ZxNHX) encoding tonoplast Na+/H+ antiporter was isolated and characterized in Zygophyllum xanthoxylum, a succulent xerophyte growing in desert areas of northwest China. The results revealed that ZxNHX consisted of 532 amino acid residues with a conserved binding domain (78LFFIYLLPPI87) for amiloride and shared high similarity (73–81%) with the identified tonoplast Na+/H+ antiporters in other plant species. Semi-quantitative RT-PCR analysis showed that the mRNA level of ZxNHX was significantly higher in the leaf than in stem or root. The transcript abundance of ZxNHX in Z. xanthoxylum subjected to salt (5–150mM NaCl) or drought (50–15% of field water capacity (FWC)) was 1.4–8.4 times or 2.3–4.4 times that of plants grown in the absence of NaCl or 70% of FWC, respectively. Leaf Na+ concentration in plants exposed to salt or drought was 1.7–5.2 times or 1.5–2.2 times that of corresponding control plants, respectively. It is clear that there is a positive correlation between up-regulation of ZxNHX and accumulation of Na+ in Z. xanthoxylum exposed to salt or drought. Furthermore, Z. xanthoxylum accumulated larger amounts of Na+ than K+ in the leaf under drought conditions, even in low salt soil. In summary, our results suggest that ZxNHX encodes a tonoplast Na+/H+ antiporter and plays important roles in Na+ accumulation and homeostasis of Z. xanthoxylum under salt and drought conditions. [Copyright &y& Elsevier]

• ZxABCG11 was cloned and characterized from the xerophyte Zygophyllum xanthoxylum. • ZxABCG11 was predominantly expressed in young leaves and was induced by salt, drought and heat, especially prominent under combined drought and heat stresses. • Ectopic expression of ZxABCG11 in Arabidopsis increased the density of wax crystals and reduced cuticle permeability. • Expression of ZxABCG11 in Arabidopsis enhanced the drought tolerance of transgenic plants by increasing cuticular wax accumulation. Cuticular waxes, a waterproofing hydrophobic barrier that coats the aerial surfaces of all terrestrial plants, protects plants from various environmental stresses, particularly drought stress. The molecular basis of cuticular wax deposition in xerophytes (e.g. desert plants), including transport mechanisms of waxes to the cell wall, is poorly understood. Here, ZxABCG11 encoding an ATP binding cassette (ABC) transporter was isolated from the xerophyte Zygophyllum xanthoxylum , since we found it was predominantly expressed in young leaves and induced by salt, drought, heat, and combined drought and heat stresses. To ascertain the function of ZxABCG11 , we introduced ZxABCG11 into Arabidopsis thaliana and found an increased abundance of cuticular wax on stems and leaves of the transgenic plants, which also exhibited a thickened cuticle and reduced cuticle permeability. Transcript expression analysis revealed that many genes related to wax biosynthesis and transport were up-regulated in these ZxABCG11 transgenic plants. Furthermore, compared with wild type Arabidopsis, ZxABCG11 transgenic plants displayed a higher biomass and survival rate under drought conditions. Taken together, we propose that the expression of ZxABCG11 in Arabidopsis promotes cuticular wax accumulation and thicker cuticle formation, thereby enhancing drought tolerance. [ABSTRACT FROM AUTHOR]

• ZxNRT1.5 was mainly expressed in the root stele of Zygophyllum xanthoxylum. • ZxNRT1.5 in roots was induced by salt treatments and osmotic stress. • ZxNRT1.5 mediated root-to-shoot NO 3 − transport and enhanced NO 3 − uptake. • ZxNRT1.5 modulated salt and drought tolerance by regulating NO 3 −, Na+, K+ transport. The Nitrate Transporter1/Peptide Transporter family member NPF7.3/NRT1.5 is responsible for long-distance transport of NO 3 − and involved in affecting salt and drought tolerance in plants. However, current studies have only focused on AtNRT1.5 from the stress-sensitive glycophyte Arabidopsis. In this study, the function of the NRT1.5 homolog ZxNRT1.5 from the typical xerophyte Zygophyllum xanthoxylum in ion transport and plants' salt and drought tolerance was analyzed. The results indicated that ZxNRT1.5 was mainly expressed in the root stele, and its expression level was significantly induced by salt treatments and osmotic stress. Overexpression of ZxNRT1.5 in Arabidopsis showed that ZxNRT1.5 mediated root-to-shoot NO 3 − transport and contributed to enhancing NO 3 − uptake. Overexpression of ZxNRT1.5 increased Na+ accumulation by decreasing the expression of AtHKT1;1 in roots, and promoted root-to-shoot transport of K+ probably by changing polarization of cell membrane under salt stress. Meanwhile, ZxNRT1.5 -overexpressing lines exhibited stronger tolerance to mannitol-induced osmotic stress, resulted from an increased accumulation of NO 3 − and the accumulation of a small quantity of Na+ that was beneficial for plant growth. These findings suggest that ZxNRT1.5 is not only essential for long-distance transport and accumulation of NO 3 −, but also involved in regulating Na+ and K+ transport, thereby modulating salt and drought tolerance. [ABSTRACT FROM AUTHOR]