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Pathogenesis-related proteins (PR), whose expressions are induced by biotic and abiotic stress, play important roles in plant defense. Previous research identified the salt-induced HcPR10 gene in the halophyte Halostachys caspica as a regulator of plant growth and development through interactions with cytokinin. However, the mechanisms by which HcPR10 mediates resistance to abiotic stress remain poorly understood. In this study, we found that the heterologous expression of HcPR10 significantly enhanced salt and drought tolerance in Arabidopsis , likely by increasing the activity of antioxidant enzyme systems, allowing for effective scavenging of reactive oxygen species (ROS) and thus protecting plant cells from oxidative damage. Additionally, the overexpression of HcPR10 also activated the expression of stress-related genes in Arabidopsis . Furthermore, using yeast two-hybrid technology, five proteins (HcLTPG6, HcGPX6, HcUGT73B3, HcLHCB2.2, and HcMSA1) were identified as potential interacting partners for HcPR10, which could positively regulate the salt stress response mediated by HcPR10. Our findings lay the foundation for a better understanding of the molecular mechanisms of HcPR10 in response to abiotic stress and reveal additional candidate genes for improving crop salt tolerance through genetic engineering. Key message Heterologous expression of HcPR10 increases salt and drought resistance in transgenic Arabidopsia and five potential HcPR10-interacting proteins were screened from Halostachys capsica cDNA libraries using a yeast two-hybrid system .

Key messageThis study demonstrated that HcKUP12 plays a major role in K+ acquisition faced with externally low K+ and high Na+ and that HcKUP12 could be regarded as a candidate gene for a high-affinity K+ uptake system.Potassium (K+) is an essential macronutrient for plant growth, development and resistance to osmotic stress. KT/HAK/KUP is the largest potassium transporter family, the members of which play crucial roles in K+ homeostasis and cell growth in various plant species. Desert halophytes need many strategies to survive in harsh environments, among which efficient absorption of K+ is an important mechanism. Here, we identified and studied HcKUP12 of the KT/HAK/KUP family from Halostachys caspica which is an important perennial halophyte of woody plants. Expression analysis showed that HcKUP12 has higher expression in assimilation branches (functioning as leaves due to leaf degeneration) than roots, and HcKUP12 was induced by salt, abscisic acid (ABA) and methyl viologen (MV) stress. Subcellular localization analysis indicated that HcKUP12 was targeted to the plasma membrane (PM). HcKUP12 gene function was evaluated using K+ uptake deficient yeast R5421 and Arabidopsis thaliana was evaluated. Transformation with HcKUP12 rescued the growth defect of mutant yeast strain R5421 at the low K+ concentration range between 0 and 50 mM. Overexpression of HcKUP12 in A. thaliana showed increased lateral roots at 100 µM (− K+) supply condition and root length at 125 mM NaCl stress, respectively. Additionally, shoot growth, potassium content and K+/Na+ concentration ratio in the seedlings of OE lines were all enhanced resulting in tolerance to low potassium and salt stress. Taken together, these results demonstrate that HcKUP12 plays a major role in K+ acquisition when faced with externally low K+ and high Na+ in HcKUP12 OE plants.

The increasing global phenomenon of soil salinization has prompted heightened interest in the physiological ecology of plant salt and alkali tolerance. Halostachys caspica  belonging to Amaranthaceae, an exceptionally salt-tolerant halophyte, is widely distributed in the arid and saline-alkali regions of Xinjiang, in Northwest China. Soil salinization and alkalinization frequently co-occur in nature, but very few studies focus on the interactive effects of various salt and alkali stress on plants. In this study, the impacts on the  H. caspica  seed germination, germination recovery and seedling growth were investigated under the salt and alkali stress. The results showed that the seed germination percentage was not significantly reduced at low salinity at pH 5.30–9.60, but decreased with elevated salt concentration and pH. Immediately after, salt was removed, ungerminated seeds under high salt concentration treatment exhibited a higher recovery germination percentage, indicating seed germination of  H. caspica was inhibited under the condition of high salt-alkali stress. Stepwise regression analysis indicated that, at the same salt concentrations, alkaline salts exerted a more severe inhibition on seed germination, compared to neutral salts. The detrimental effects of salinity or high pH alone were less serious than their combination. Salt concentration, pH value, and their interactions had inhibitory effects on seed germination, with salinity being the decisive factor, while pH played a secondary role in salt-alkali mixed stress.

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is a key enzyme in the glycolytic pathway. GAPDHs contribute to many non-glycolytic processes such as transcriptional regulation, DNA repair, signal transduction cascades, autophagy, and apoptosis in mammalian cells. In plants, GAPDH has been implicated in the response to salt stress, but precisely how its functions in this regard remains unclear. In the present study, we identified an GAPDH gene from the Chenopodiaceae euhalophyte Halostachys caspica ( HcGAPDH ) as a senescence component of the plant salt stress response. Enhanced expression of HcGAPDH was observed under salt stress and abscisic acid treatment. Green fluorescent protein-tagged HcGAPDH localized to the cytosol of transgenic Arabidopsis thaliana cells, and salt stress induced the translocation of HcGAPDH protein into the nucleus, which was different from carbohydrate-mediated feedback signaling. Ectopic expression of HcGAPDH resulted in retarded growth of Arabidopsis plants and suppressed chlorophyll production, and darkness accelerated chlorotic leaf senescence in HcGAPDH- overexpressing lines. Moreover, the transcript levels of senescence-associated genes were markedly increased in transgenic plants compared to WT and atgapdh mutants. Taken together, the data indicate that under salt stress conditions, HcGAPDH translocates from the cytosol to the nucleus and functions in senescence regulation.

Background and aims Soil alkaline salinity restricts the deep utilization of land resources. Research on the composition and diversity of plant rhizosphere microbial communities in saline-alkaline soils is helpful for identifying important microbial functional groups or functional potential, which is of great significance for vegetation restoration and ecological reconstruction. Methods Bacteria colonized the rhizosphere soil of three halophytes grown in desert grasslands, including Halocnemum strobilaceum (HS), Phragmites communis (PC), and Halostachys capsica (HC), under moderate, heavy, and severe saline-alkaline conditions. Halophytes were then analysed via 16S amplicon sequencing. The relationships between soil physicochemical characteristics and bacterial diversity were determined via redundancy analysis (RDA) and Spearman correlation analysis. Results As the saline-alkali levels increased, the bacterial richness and diversity decreased in the PC and HS groups but were greater in the severe grade than in the heavy grade in the HC group. The bacterial communities in the PC, HS, and HC treatments at different saline-alkali levels were significantly different. Moreover, the rhizosphere bacterial communities were sensitive to changes in the saline-alkaline environment. Proteobacteria, Actinobacteriota, Bacteroidota, and Halobacterota were the predominant phyla for PC, HS, and SC in moderate, heavy, and severe saline-alkaline soils, respectively. EC and pH affected the richness and β diversity of the bacterial communities of all the assayed halophytes, regardless of the saline-alkaline level. Conclusion Our findings suggested that rhizosphere bacterial communities may play a role in halophyte adaptation to saline-alkali land, as well as promoting plant growth and improving ecological performance.

The APETALA2 (AP2) and ethylene-responsive element-binding factor (ERF) gene family is one of the largest plant-specific transcription factor gene families, which plays a critical role in plant development and evolution, as well as response to various stresses. The TARGET OF EAT3 ( TOE3 ) gene is derived from Halostachys caspica and belongs to the AP2 subfamily with two AP2 DNA-binding domains. Currently, AP2 family mainly plays crucial roles in plant growth and evolution, yet there are few reports about the role of AP2 in abiotic stress tolerance. Here, we report HcTOE3 , a new cold-regulated transcription factor gene, which has an important contribution to freezing tolerance. The main results showed that the expression of HcTOE3 in the H. caspica assimilating branches was strongly induced by different abiotic stresses, including high salinity, drought, and extreme temperature (heat, chilling, and freezing), as well as abscisic acid and methyl viologen treatments. Overexpressing HcTOE3 gene (OE) induced transgenic Arabidopsis plant tolerance to freezing stress. Under freezing treatment, the OE lines showed lower content of malondialdehyde and electrolyte leakage and less accumulation of reactive oxygen species compared with the wild type. However, the survival rates, antioxidant enzyme activities, and contents of osmotic adjustment substance proline were enhanced in transgenic plants. Additionally, the OE lines increased freezing tolerance by up-regulating the transcription level of cold responsive genes ( CBF1 , CBF2 , COR15 , COR47 , KIN1 , and RD29A ) and abscisic acid signal transduction pathway genes ( ABI1 , ABI2 , ABI5 , and RAB18 ). Our results suggested that HcTOE3 positively regulated freezing stress and has a great potential as a candidate gene to improve plant freezing tolerance.

Condensation water has been a recent focus in ecological hydrology research. As one of the main water sources that maintains the food chain in arid regions, condensation water has a significant impact on water balance in arid environments and plays an important role in desert vegetation. This study takes drought desert areas and high-salinity habitats as its focus—selecting Halostachys caspica (M.Bieb.) C.A.Mey. and its community in mild, moderate, and severe salinity soil—analyzed the source of condensation water utilized by these plants, and calculated its percentage of contribution. I. Study results revealed: (1) Scale-like leaves can absorb condensation water and the order of condensation water contribution to plant growth in different salinity habitats are severe > mild > moderate, such that the average contribution rates were 11.13%, 7.10%, and 3.79%, respectively; (2) The migration path of water movement in these three communities are formed in two main ways: (a) rain and condensation water recharge the soil to compensate for groundwater, while some groundwater compensates for river water and partially returns to the atmosphere by soil evaporation and plant transpiration; and (b) rain and condensation water directly compensate for river water and plant roots absorb river water, groundwater, and soil water in order to grow; (3) in mild habitats, the water movement path in plants is as follows: shallow root → stem → branches → leaves and shallow root → deep root; (4) in moderate habitats, stems act as the bifurcation point and the path follows as: stem → branches → leaves and stem → shallow root → deep root; and (5) in severe habitats, the path is as follows: deep root → shallow root → stem → branches → leaves, and finally returning to the atmosphere. These results elucidate the contribution of condensation water on Halostachys caspica growth and the migration path through the Halostachys caspica body. Condensation water obtained by Halostachys caspica communities in different salinity habitats provides a theoretical basis and data supporting the need for future research of condensation water on plants at the physiological level in arid regions and provides reference for the protection of saline soil and its ecological environment in arid regions.

Because of global warming, desertification is increasing. One of the best strategies for combating desertification is reforestation of forests and biological operations of vegetation. However, events like soil salinity and dust storms, as the most important manifestations of desertification, prevent vegetation from settling in these areas. In this study, the effects of two halotolerant plant growth-promoting rhizobacterial strains, Bacillus pumilus HR and Zhihengliuella halotolerans SB, on physiological and nutritional status of the desert halophyte Haloxylon aphyllum under the stress of salinity (0, 300, and 600 mM NaCl) and dust (0 and 1.5 g m −2 month −1 ) were examined. Under dust application, the Z. halotolerans SB strain compared to the B. pumilus HR strain and the combination of these two bacterial strains improved the content of total chlorophyll (247 and 316%), carotenoid (94 and 107%), phosphorus (113 and 209%), magnesium (196 and 212%), and total dry biomass (13 and 28%) in H. aphyllum at salinity levels of 300 and 600 mM NaCl, respectively. Under conditions of combined application of dust and salinity, B. pumilus HR compared to Z. halotolerans SB and the combination of two strains at salinity levels of 300 and 600 mM NaCl, respectively, had better performance in increasing the content of iron (53 and 69%), calcium (38 and 161%), and seedling quality index (95 and 56%) in H. aphyllum . The results also showed that both bacterial strains and their combination were able to reduce the content of ascorbic acid, flavonoid, total phenol, proline, and malondialdehyde, and catalase activity, and ultimately improve the antioxidant capacity of H. aphyllum . This showed that the use of halotolerant rhizobacteria can stop the production of free radicals and thus prevent cell membrane damage and the formation of malondialdehyde under salinity and dust stress. The results of this study for the first time showed that halotolerant rhizobacteria can increase the seedling quality index of H. aphyllum under combined conditions of salinity and dust. The use of these bacteria can be useful in the optimal afforestation of H. aphyllum species in arid and semi-arid ecosystems.

Salt and drought are the major abiotic stress factors plaguing plant growth, development and crop yields. Certain abiotic-stress tolerant plants have developed special mechanisms for adapting to adverse environments in the long process of evolution. Elucidating the molecular mechanisms by which they can exert resistance to abiotic stresses is beneficial for breeding new cultivars to guide agricultural production. Halostachys caspica , a perennial halophyte belonging to Halostachys in Amaranthaceae, is extremely tolerant to harsh environments, which is commonly grown in the saline-alkali arid desert area of Northwest, China. However, the molecular mechanism of stress tolerance is unclear. Nuclear Factor Y-A (NFYA) is a transcription factor that regulates the expression of downstream genes in plant response to adverse environments. It has also been reported that some members of the NFYA family are the main targets of miR169 in plants. In this study, we mainly focused on exploring the functions and preliminary mechanism of the miR169b/NFYA1 module from H. caspica to abiotic stress. The main results showed that RLM-RACE technology validated that HcNFYA1 was targeted by HcmiR169b, qRT-PCR revealed that HcmiR169b was repressed and HcNFYA1 was induced in the H. caspica branches under various abiotic stress as well ABA treatment and Arabidopsis stable transformation platform with molecular methods was applied to elucidate that the HcmiR169b/HcNFYA1 module conferred the salt and drought tolerance to plants by enhancing ABA synthesis and ABA signal transduction pathways, maintaining ROS homeostasis and the stability of cell membrane. HcNFYA1 is expected to be a candidate gene to improve plant resistance to salt and drought stresses.

To adapt to a habitat, halophytes growing at the same saline–alkali levels develop their unique rhizosphere microbial communities, whereas same plant species growing at different saline–alkali levels have different rhizosphere microbial communities. Therefore, understanding the rhizosphere microbial community structure of halophytes in different saline–alkali soils can help explore the microbial diversity and functional potential of important soil microorganisms. In this study, rhizosphere soils of three typical halophytes, namely, Halocnemum strobilaceum , Phragmites communis , and Halostachys caspica , growing at severe, heavy, and moderate saline–alkali soils, respectively, were collected from southern Xinjiang. The community structure and physicochemical properties of fungal species in the total nine rhizosphere soils were investigated. Furthermore, the differences in the fungal community structure, diversity, and ecological functions were analyzed in terms of the extent of saline–alkali level and host plant specificity. Rhizosphere soils in the nine habitats had different physicochemical properties. In terms of host plant type, rhizosphere fungal species diversity and richness were the highest in P. communis , followed by H. caspica and H. strobilaceum . The fungal community diversity and richness followed the pattern of moderate > severe > heavy in different soil salinity and alkali types. Although the three host plants had similar rhizosphere fungal community structures under moderate and heavy saline–alkali conditions, these varied significantly under extremely severe saline–alkali conditions. In total, 315 species were identified across all samples, and they were affiliated with 12 phyla, 37 classes, 69 orders, 138 families, and 244 genera. The number of jointly owned ASVs was 189. In the nine habitats, Ascomycota and Basidiomycota were the dominant phyla, while Alternaria , Neocamarosporium , Filobasidium , and Acremonium were the common dominant genera. A prediction of fungal community functions revealed pathotroph-saprotroph-symbiotroph and saprotrophs to be dominant. At the same saline–alkali level, the functional clustering distance of fungal communities was closer. Factors such as soil organic matter (SOM), available nitrogen (AN), electronic conductivity (EC), and pH contributed to the distribution of microbial communities. This study revealed both similarities and distinctions in the composition of fungal communities within the rhizosphere soils of the three typical halophytes thriving in various saline–alkali habitats. At moderate and heavy saline–alkali levels, the fungal community structures were markedly influenced by the severity of salinity and alkalinity. In extremely severe saline–alkali soils, the host plant type significantly affected the fungal community structure. Ultimately, these findings lay a theoretical foundation for the improvement of soil and crop yield in saline–alkali land.