In order to explore the response mechanism of Lilium pumilum (L. pumilum) to saline–alkali stress, we successfully cloned LpGDSL (GDSL lipase, Gly-Asp-Ser-Leu) from L. pumilum. The qRT-PCR results indicated that the LpGDSL expression was higher in the leaves of L. pumilum, and the expression of the LpGDSL reached the highest level at 12 h in leaves under 11 mM H₂O₂, 200 mM NaCl, 25 mM Na₂CO₃, and 20 mM NaHCO₃. The bacteriophage overexpressing LpGDSL was more tolerant than the control under different NaHCO₃ contents. Overexpressed and wild-type plants were analyzed for phenotype, chlorophyll content, O₂⁻ content, H₂O₂ content, lignin content, and so on. Overexpressed plants had significantly higher resistance than the wild type and were less susceptible to saline–alkali stress. The yeast two-hybrid and BiFC assays demonstrated the existence of an interaction between LpGDSL and LpBCP. The yeast one-hybrid assay and transcriptional activation assay confirmed that B3 transcription factors could act on LpGDSL promoters. Under saline–alkali stress, L. pumilum will promote the expression of LpGDSL, which will then promotes the accumulation of lignin and the scavenging of reactive oxygen species (ROS) to reduce its damage, thus improving the saline–alkali resistance of the plant.

Soil salinization severely impacts plant cultivation. Lilium pumilum (L. pumilum) exhibits tolerance to saline–alkali stresses. One Bacillus cereus strain, LpBc-47, possesses the ability of growth promotion and saline–alkali tolerance. The microbial diversity of L. pumilum was assessed through metagenomic sequencing. LpBC-47 obtained from L. pumilum was subjected to physiological and biochemical analyses and whole-genome sequencing. The effects of endophytic bacteria on plants were evaluated by measuring growth parameters, physiological indices, antioxidant enzyme activities, and ROS content. Microbial diversity analysis revealed that the abundance of endophytic bacteria in L. pumilum decreased under saline–alkali conditions, whereas the abundance of Bacillus cereus increased. Physiological and biochemical analysis showed that LpBC-47 has the characteristics of promoting growth and reducing plant damage caused by salt–alkali stress, such as phosphorus solubilization, nitrogen fixation, siderophore production, IAA, and ACC deaminase synthesis. Genomic analysis revealed that LpBC-47 contains growth-associated and stress-alleviation genes. GFP indicated the colonization of LpBc-47 in the roots and bulbs of L. pumilum. The LpBc-47 inoculant plant increased leaf length and dry weight, elevated proline and chlorophyll levels, enhanced antioxidant enzyme activity, and reduced oxidative damage. This study highlights the potential of LpBc-47 for improving plant growth under saline–alkali conditions.

BEL1-like homeodomain protein 3 (BLH3) plays a crucial role in plant development. However, its involvement in the salt stress response has not been studied. In this study, we investigated the molecular mechanism underlying the response of LpBLH3 to salt stress in Lilium pumilum (L. pumilum) using various techniques, including quantitative PCR (RT-qPCR), determination of physiological indices of plant after Saline-Alkali stress, yeast two-hybrid screening, luciferase complementation imaging (LCI), and chromosome walking to obtain the promoter sequence, analyzed by PlantCARE, electrophoretic mobility shift assay (EMSA), and then dual-luciferase reporter assay(LUC). RT-qPCR analysis revealed that LpBLH3 is most highly expressed in the leaves of L. pumilum. The expression of LpBLH3 peaks at 24 or 36 h in the leaves under different saline stress. Under various treatments, compared to the wild type (WT), the LpBLH3 overexpression lines exhibited less chlorosis and leaf curling and stronger photosynthesis. The overexpression of LpBLH3 can enhance lignin accumulation in root and stem by positively modulating the expression of crucial genes within the lignin biosynthesis pathway. Y2H and LCI analyses demonstrated that LpBLH3 interacts with LpKNAT3. Additionally, EMSA and LUC analyses confirmed that LpBLH3 can bind to the promoter of LpABI5 and upregulate the expression of ABI5 downstream genes (LpCAT1/LpATEM/LpRD29B). In summary, LpBLH3 enhances the plant’s salt tolerance through the ABA pathway and lignin synthesis. This study can enrich the functional network of the BLH transcription factor family, obtain Lilium pumilum lines with good saline-alkali resistance, expand the planting area of Lilium pumilum, and improve its medicinal and ornamental values. Additionally, the functional analysis of the BLH transcription factor family provides new insights into how crops adapt to the extreme growth environment of saline-alkali soils.