Soil salinization is a major constraint on global agricultural production. According to the Food and Agriculture Organization, more than 800 million hectares of arable land are affected by salinization, and this trend is expected to continue [1]. Salinized soils severely limit crop growth and yield, causing substantial economic losses in global crop production [2], [3]. Therefore, improving plant salt tolerance is a key strategy for reclaiming saline-alkaline lands and promoting sustainable agriculture [4], [5].

Halophytes such as Suaeda salsa, Salicornia europaea and Glaux maritima are pioneer species in saline environments because of their exceptional salt tolerance [6], [7], [8]. Compared with glycophytes, halophytes have evolved distinctive morphological and physiological adaptations to mitigate salt toxicity, including succulence, salt-storing vacuoles, reinforced cell walls and accumulation of inorganic salts or compatible solutes to maintain turgor [9], [10]. By contrast, most cereal crops including rice, wheat and maize, are salt sensitive and perform poorly in saline soils [4], [11], [12]. Understanding the mechanisms that underpin halophyte salt tolerance is therefore essential for engineering or breeding crops with improved resilience to salinity.

Excess sodium (Na+) is a principal cause of salt stress, causing osmotic shock, ion toxicity and oxidative damage that impair plant growth and development [13], [14]. Plants deploy multiple tolerance mechanisms, including osmotic adjustment, ion homeostasis and antioxidant defenses [15]. Central to these responses is maintenance of Na+/K+ homeostasis, achieved through selective transport, efflux and vacuolar compartmentalization mediated by membrane transporters. For example, Na+ is extruded from the cytoplasm or sequestered into vacuoles by transporters such as SOS1, NHXs and HKTs, thereby reducing cytosolic Na+ toxicity [10], [16]. SOS1, in particular, mediates Na+ extrusion in roots, while NHX family members facilitate vacuolar sequestration of Na+ [17], [18], [19].

Potassium (K+) acts as a critical counter-ion that alleviates Na+ toxicity by maintaining cellular K+/Na+ balance [12], [20]. In barley, transporters such as HvHKT2;1 modulate Na+/K+ fluxes between roots and shoots, contributing to salt tolerance. A suite of K+ transporters and channels (e.g., GORK, HAK, AKT/KAT) cooperate to sustain K+ uptake and cellular K+/Na+ balance [21], [22], [23], [24]. Plasma-membrane and tonoplast H+-ATPases generate the proton motive force that energizes many of these transport processes [25], [26]. Calcium signaling is also central to ionic regulation, activating downstream pathways that help restore ion homeostasis under saline conditions [27], [28], [29].

Beyond ionic toxicity, high salinity lowers soil water potential and provokes osmotic stress; plants respond by accumulating compatible solutes such as proline, sugars and betaines to maintain turgor and metabolic activity [30]. Whereas glycophytes commonly synthesize organic osmolytes, many halophytes tolerate high external salt by compartmentalizing inorganic ions (e.g., Na+) in vacuoles to raise osmotic potential while avoiding cytotoxicity [31]. Some halophytes possess specialized salt-secreting structures that enable efflux or sequestration of excess salts at the tissue surface [32].

However, high salinity inevitably triggers the excess production of reactive oxygen species (ROS), which can oxidatively damage the very lipid membranes and proteins that harbor these transporters [33], [34], [35]. Consequently, the antioxidant system including both enzymatic and non-enzymatic components is not merely a secondary defense but a prerequisite for sustained ion transport. Enhancing antioxidant capacity, whether via increased enzyme activities or elevated antioxidant pools, can substantially improve tolerance to oxidative damage [35], [36].

Among the halophytic relatives of crops, H. marinum (sea barleygrass) thrives in coastal soil and exhibits markedly higher salt tolerance than cultivated barley or wheat [37], [38]. Its potential for gene transfer or introgression into crop germplasm has therefore attracted considerable interest, making H. marinum a valuable genetic resource for improving salt tolerance in cereals [39], [40]. Previous physiological studies indicate that H. marinum restricts Na+ and Cl− accumulation in aerial tissues while enhancing the accumulation of compatible solutes (e.g., proline, glycine betaine) and the activities of antioxidant enzymes under salinity. In addition, its roots maintain relatively low cytosolic Na+ level and a high K+/Na+ ratio through effective Na+ extrusion and K+ retention [41], [42], [43]. Although these physiological traits are well documented, the proteomic responses underlying salt tolerance in H. marinum remain poorly characterized.

Proteomics offers a powerful approach to dissect plant responses to abiotic stress by revealing key regulatory proteins and their dynamic changes [44]. Orbitrap Astral-DIA quantitative proteomics provides high sensitivity, extended dynamic range and rapid acquisition speed, enabling deep and reproducible proteome coverage in complex plant tissues [45], [46]. In this study, we employed the Astral-DIA proteomics to systematically profile proteome dynamics in the roots of H. marinum under saline conditions. Through combined proteome-transcriptome analyses, we highlight ion transport systems and antioxidant metabolism, most notably glutathione metabolism, as central components of the salt-tolerance network in H. marinum, and we propose a regulatory model that may guide the development of salt-tolerant crops.