Table 1.

Examples of adaptations of tolerant halophytic plants to salinity. Ref.: references.

Level of study	Salinity adaptation	Ref.
Genomic	Gene duplication (increased gene copy number) and promoter adaptation of several salinity-responsive genes (transcription factors: Myb24, ATPase AVP1, ion transporters: SOS1, NHX; ABC)	[18]
Transcriptomic	Enhanced constitutive expression of several salinity-responsive transcripts (SOS1, SOD, P5CS, GS, INPS, cytochrome P450, heat shock protein ) Hsc70-3, antifugal protein PDF1.2)	[19–21]
Proteomic	Enhanced abundance of several stress- and defence-related proteins (LEA, redox, PR), ion transporters, protective proteins involved in activation of photosynthesis (D2 protein) and protein biosynthesis, activation of biosynthesis of protective compounds (lignin)	[22–27]
Metabolomic	Alterations in carbohydrate metabolism—activation of catabolism (glycolysis, Krebs cycle, starch degradation), enhanced biosynthesis of organic osmolytes, phenolic compounds, lignin)	[20,22, 28,29]
	Osmotic effect of salinity
Functional (physiological) level	- osmotic adjustment (accumulation of low-molecular organic osmolytes and proteins—LEA proteins)	[21,30–33]
	- adjustment to mechanical stress (increased cell wall lignification, accumulation and oligomerization of several coat proteins in plasmamembrane of Dunaliella salina)	[27,28, 32,34]
	Ion-related effects of salinity
	- salt ion exclusion (increased abundance and activity of plasma membrane ion transporters (SOS1), increased lignification of xylem vessels (long-distance transport of excluded salt ions via transpiration stream— Salicornia europaea)	[27]
	- salt ion intracellular compartmentation (salt import into vacuoles— an enhanced abundance of tonoplast ion transporters NHX, support of ion transport - H+-ATPase and FBP aldolase activity)	[24,35]