Plant-Derived Haloalkaliphile From Cistanche: Genomic–Metabolomic Insights Into Strain A8 For Saline–Alkali Soil And Crop Enhancement

Discussion

 

Current state of research on cultivable endophytes from Cistanche

Research on cultivable endophytes associated with Cistanche remains limited. Lin et al. [10] isolated an endophytic Streptomyces (strain AC‑2) and a Penicillium chrysogenum from Cistanche roots, with the latter showing notable neuroprotective activity in SH‑SY5Y cells. Yu et al. [11] reported that the abundance and diversity of cultivable endophytic fungi in Cistanche vary by season, origin, and medicinal plant part. Petrosyan et al. [12] demonstrated that seed endophytes from the holoparasite Cistanche phelypaea can promote plant growth and confer salt tolerance traits. However, to our knowledge, alkaliphile- and haloalkaliphile-tolerant endophytic bacteria from Cistanche have not been reported before this work.

 

Cistanche deserticola

 

 

 

Defining haloalkaliphiles and positioning strain A8

Across the literature, "haloalkaliphiles" are typically defined as microbes with optimal growth at salt concentrations ≥3% and pH ≥9.0; most strains tolerate pH 7–11 and 0–15% salinity [13]. Strain A8 grows optimally at 0–5% salt and pH 9, supporting its preliminary designation as a haloalkaliphilic/alkalitolerant bacterium. Remarkably, A8 maintained growth at pH 13, which is rare even among haloalkaliphiles. While such microbes are usually isolated from saline or alkaline environments (e.g., salt-lake sediments, salterns, the Dead Sea, mangrove sediments, and rhizosphere soils) [14], our study reports A8 as the first alkaliphile-like, salt‑alkali‑tolerant Bacillaceae (pseudo‑alkaliphilic Bacillus) strain isolated from a plant host (Cistanche).

Mechanistic basis for salt‑alkali tolerance in A8

Salt‑alkali tolerance is mechanistically complex. Compared with non‑tolerant bacteria, tolerant strains more strongly activate Na+/H+ antiporters and related ion transport systems to regulate intracellular osmotic pressure, enabling growth in saline–alkaline conditions [15]. Genome analysis of A8 identified 10 classes of genes implicated in salt‑alkali tolerance, including:

Transporters for compatible solutes (e.g., glycine betaine transporters) and trehalose synthesis genes;

Multiple antiporters (Na+/H+ antiporters, basic amino acid antiporters);

 

Potassium transporters and F0F1 ATP synthase.

 

Prior studies show that glycine betaine and trehalose are widespread in halophiles as compatible solutes for osmotic adjustment [15,16]. Potassium transport and antiport systems can acidify the cytoplasm to mitigate electrophilic stress, thereby enhancing environmental resilience [4]. Our data support that A8 coordinates multiple genetic modules to synthesize higher intracellular levels of proline, glycine, betaine, and trehalose and to transport Na+, K+, and H+ ions, maintaining osmotic balance and supporting normal cellular functions under saline–alkaline stress.

Biofilms, secondary metabolism, and osmoadaptation

Because transmembrane transport depends on membrane properties, biofilm formation is closely linked to salt‑alkali tolerance. Wang et al. [17] showed that strains produce more biofilm under saline–alkaline stress to alleviate salt injury. Transcriptomic and metabolic evidence suggests that biosynthesis of sesquiterpenes and triterpenes is associated with stress resistance in plants [18,19]; analogous pathways may intersect with bacterial stress programs. Proline is a key compatible solute synthesized by bacteria in response to high salt [20,21]. In our pathway enrichment analysis of upregulated and unique metabolites in A8 under saline–alkaline stress, we identified:

Purine and steroid pathways that may enhance biofilm synthesis and thus salt‑alkali tolerance;

Strong links between sesquiterpene/triterpene biosynthesis and stress resilience;

Lysine metabolism with potential to attenuate salt stress [22];

Pantothenate and CoA biosynthesis pathways that increase energetic capacity, fueling transport of saline–alkali ions.

Collectively, we propose that A8 employs a multifactorial strategy-membrane/biofilm modulation, compatible solute accumulation, and ion homeostasis-to thrive under extreme pH and salinity.

 

Wecistanche's cistanche cultivate base in yuto,xinjiang

Supportive Service Of Wecistanche-For more details about cooperation
Email:wallence.suen@wecistanche.com

 

 

Research motivation for Cistanche as a scientific crop

 

Microbiome-enabled crop development: As a holoparasitic medicinal plant adapted to arid and often saline habitats, Cistanche may host unique endophytes with exceptional haloalkaliphilic traits. Isolating and functionally characterizing such strains (e.g., A8) opens avenues for microbiome-assisted breeding and inoculant development to improve Cistanche cultivation on marginal (saline–alkali) lands.

Soil rehabilitation and bioinoculants: A8's tolerance profile suggests potential as a chassis strain for saline–alkali soil improvement. Field trials could test direct inoculation into saline–alkali soils, monitoring physico-chemical indices to quantify amelioration effects.

Plant performance enhancement: Applying A8 via rhizosphere inoculation, foliar spray, or root drench to Cistanche hosts or to nurse crops could enhance salt‑alkali resistance, survival, and biomass, directly supporting standardized cultivation and raw‑material quality.

Mechanistic validation pipeline: Integrate genomics (antiporter/compatible solute gene clusters), metabolomics (UPLC–MS/MS solute and membrane‑lipid signatures), and phenotyping (biofilm metrics, growth curves at pH 6–13 and 0–17% salinity) to establish robust mode‑of‑action dossiers for regulatory and industrial adoption.

 

Future work

Future studies will evaluate A8 in application scenarios: direct soil inoculation in saline–alkali fields with longitudinal soil property measurements; and plant‑level interventions (rhizosphere inoculation, foliar application, root drench) with assays of plant salt‑alkali tolerance. These data will enable full assessment of A8's plant‑promotion potential and support development of microbial fertilizers for Cistanche cultivation and broader saline agriculture.

 

Conclusion

 

We isolated 50 cultivable endophytic bacterial strains from Cistanche. Among them, strain A8 is, to our knowledge, the first alkaliphile‑like, salt‑alkali‑tolerant Bacillaceae (pseudo‑alkaliphilic Bacillus) strain isolated from a plant host. A8 grows across 0–17% salinity (optimal 0–5%) and pH 6.0–13.0 (optimal pH 9) and actively shifts culture pH toward its growth optimum. Genomic and UPLC–MS/MS metabolomic analyses converge to indicate that A8 maintains osmotic balance-and thus normal cellular function-by synthesizing elevated levels of compatible solutes (e.g., betaine, proline, trehalose) and by transporting Na+, K+, and H+ via multiple antiporters and transport systems. These insights provide a mechanistic foundation for leveraging A8 in saline–alkali soil improvement, microbial fertilizer development, and enhancement of plant salt‑alkali tolerance, offering a strategic resource for Cistanche crop research and standardized cultivation.

 

References

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