Trends in genetic engineering of plants with (Na⁺/H⁺) antiporters for salt stress tolerance

Figures & data

Table 1. List of abiotic stress-tolerant transgenic plants with ion transporters.

Target	Host	Gene	Tolerance	Trait improvement	Reference
Arabidopsis thaliana	Triticum aestivum	TNHX1, TVP1	Salt, drought	Imroved shoot growth	Brini et al. [48]
Arabidopsis thaliana	Suaeda salsa	SsNHX1	Salt, freezing	Normal plant growth at 200 mmol/L NaCl and -7 °C	Li et al. [49]
Arabidopsis thaliana	Solanum lycopersicum	LeNHX2	Salt	Better growth and high fresh weight	Rodriguez-Rosales et al. [73]
Arabidopsis thaliana	Medicago sativa	MsNHX1	Salt	Better germination and seedling growth	An et al. [50]
Arabidopsis thaliana	Arabidopsis, cotton, Suaeda salsa, wheat, yeast	GhNHX1, ScNHX1, AtNHX1, SsNHX1, TaNHX1	Salt, drought	High salt tolerance and photosynthetic activity. Growth performance under salt stress was ranked as GhNHX1 > ScNHX1 > AtNHX1 > SsNHX1 > TaNHX1	Liu et al. [74]
Beta vulgaris	Arabidopsis thaliana	AtNHX3	Salt	Increased yield of storage roots	Liu et al. [52]
Brassica juncea	Pennisitum glaucum	pgNHX1	Salt	Retained normal plant growth and seed yield at 300 mmol/L NaCl	Rajagopal et al. [75]
Gossipium hirsutum	Arabidopsis thaliana	AtNHX1	Salt	25% higher fibre yield under 200 mmol/L NaCl under greenhouse and field conditions	He et al. [71]
Gossipium hirsutum	Gossipium hirsutum	AVP1	Salt, drought	20% higher fibre yield in transgenic lines than that of wild-type under filed condition	Pasapula et al. [72]
Jatropha	Salicornia brachiata	SbNHX1	Salt	Salt tolerance up to 200 mmol/L NaCl	Jha et al. [76]
Madicago sativa	Triticum aestivum	TaNHX2	Salt	High antiporters activity under 200 mmol/L NaCl	Zhang et al. [77]
Nicotiana tabaccum	Gossipium hirsutum	GhNHX1	Salt	About 100% increase in dry weight	Wu et al. [53]
Nicotiana tabaccum	Hordeum brevisubulatum	HbNHX1	Salt	Increased dry weight	Lu et al. [55]
Nicotiana tabaccum	Synechocystis	Na^+/H^+ antiporter	Salt	Increased biomass and seed production	Hossain et al. [56]
Nicotiana tabaccum	Aeleuropus littoralis	AlNHX1	Salt	More Na^+ accumulation in roots. High K^+/Na^+ ratio in shoots. About 150% increase in dry weight/plant	Zhang et al. [58]
Nicotiana tabaccum	Arabidopsis thaliana	AtNHX1	Salt	–	Soliman et al. [57]
Nicotiana tabaccum	Salicornia brachiata	SbSOS1	Salt	Enhanced plant growth	Yadav et al. [78]
Oryza sativa	Oryza sativa	OsNHX1	Salt	Delayed flowering and growth retardation	Chen et al. [61]
Oryza sativa	Pennisetum glaucum	PgNHX1	Salt	Improvement in shoot and root length	Verma et al. [62]
Petunia hybrida	Arabidopsis thaliana	AtNHX1	Salt, drought	–	Xu et al. [79]
Festuca arundinacea	Arabidopsis thaliana	AtNHX1	Salt	Improved shoot and root dry weight	Zhao et al. [80]
Triticum aestivum	Arabidopsis thaliana	AtNHX1	Salt	Increase in shoot and root dry weight	Xue et al. [64]
Zea mays	Oryza sativa	OsNHX1	Salt	Increased biomass production	Chen et al. [66]

Figure 1. Schematic representation of Na⁺ transport across the cellular and vacuolar membranes. Na⁺/K⁺ homeostasis is established by various specific and non-specific cation channels. High Na⁺ content enters the cytoplasm through the non-selective cation channels (NSCC), the outward-rectifying K⁺ channels (KORC) and the high Na⁺ affinity HKT1 antiporter. Proton gradient across the plasma membrane is established by plasma membrane ATPase (PM-ATPase). Excess Na⁺ is taken inside the vacuole through vacuolar membrane NHX1. The proton gradient across the vacuolar membrane is established by H⁺-pyrophosphatase (AVP1) and the vacuolar H⁺-ATPase (V-ATPase).

Table 2. List of potential halophytes to be used for salt tolerance improvement in crop plants.

Halophytes	Important species	Monocot/dicot	Uses	Distribution
Amshot grass (Echinochloa spp)	Echinochloa stagninum	Monocot	Bio-reclamation of saline–sodic soils	Africa, Asia
Salt water cordgrass (Spartina spp)	Spartina alterniflora, S. anglica	Monocot	Sediment stabilization, nursery for fish and invertebrates	Asia, America, Australia, Europe
(Aeluropus spp)	Aeluropus littoralis, A. lagopoidus, A. pilosus	Monocot	Used as a fodder crop	Asia, Africa
Dropseed grasses (Sporobulus spp)	Sporobulus virginicus, S. fertilis, S. pyramidatus	Monocot	Used as feed
Salt bush (Atriplex spp)	Atriplex amnicola, A. nummularia, A. undulata	Dicot	Used as feed	All over the world
Salt cedar (Tamarix spp)	Tamarix chinensis, T. parviflora, T. ramosissima	Dicot	–	Europe, Asia, Africa
Sea blite (Suaeda spp)	Suaeda vera, S. maritime	Dicot	–	Coastal Mediterranean areas, Europe
Summer cyprus (Kochia spp)	Kochia scoparia	Dicot	Used as forage	Eurasia, North America
Saltwort (Salicornia spp)	Salicornia virginica, S. europaea, S. bigelovii	Dicot	Used as food by Lepidoptera species	Europe, Asia, North America
Russia thistle (Salsola spp)	Salsola soda, S. kali, S. iberica	Dicot	Used as feed	Asia, Africa

Note: (–) information not available.

Figure 2. Manipulation of halophytes salt tolerance mechanisms in transgenic glycophyte crop plants.

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