Cell wall reconstruction and DNA damage repair play a key role in the improved salt tolerance effects of He-Ne laser irradiation in tall fescue seedlings

Integrated analysis of miRNA-mRNA regulatory networks in Anoectochilus roxburghii in response to blue laser light

Anoectochilus roxburghii (Wall.) Lind. has significant medicinal and economic value, and the social demand for this species is increasing annually. Laser light sources have different luminescent mechanisms compared with ordinary light sources and are also important factors regulating the synthesis of functional metabolites in A. roxburghii. However, the regulatory mechanism through which A. roxburghii responds to blue laser light has not been investigated. Previous studies have shown that blue-laser treatment results in more red leaves than blue- or white-light treatment. Here, the differences in the effects of laser treatment on A. roxburghii were analyzed by transcriptome sequencing. Gene Ontology analysis revealed that the membranes, calcium ion binding, brassinosteroid-mediated signaling pathway and response to salicylic acid play important roles in the response of A. roxburghii to blue laser light. Kyoto Encyclopedia of Genes and Genomes analysis revealed the involvement of multiple pathways in the response to blue-laser treatment, and among these, beta biosynthesis, flavone and flavonol biosynthesis, thiamine metabolism, limonene and pinene biosynthesis, and peroxisomes play core roles. Cytoscape interaction analysis of the differentially expressed miRNA targets indicated that novel_miR_66, novel_miR_78 and novel_miR_212 were most likely involved in the effect of blue laser light on A. roxburghii. Metabolic content measurements showed that blue laser light increased the beet red pigment, thiamine, total flavonoid and limonene contents, and qPCR analysis confirmed that novel_miR_21, novel_miR_66, novel_miR_188 and novel_miR_194 might participate in the blue-laser signaling network through their target genes and thereby regulate the functional metabolite accumulation in A. roxburghii. This study provides a scientific basis for high-yield A. roxburghii production.

Isolation and identification of plant growth-promoting rhizobacteria from tall fescue rhizosphere and their functions under salt stress

Soil salinity has become one of the major factors that threaten tall fescue growth and turf quality. Plants recruit diverse microorganisms in the rhizosphere to cope with salinity stress. In this study, 15 plant growth-promoting rhizobacteria (PGPR) were isolated from the salt-treated rhizosphere of tall fescue and were annotated to 10 genera, including Agrobacterium, Fictibacillus, Rhizobium, Bhargavaea, Microbacterium, Paenarthrobacter, Pseudarthrobacter, Bacillus, Halomonas, and Paracoccus. All strains could produce indole-3-acetic acid (IAA). Additionally, eight strains exhibited the ability to solubilize phosphate and potassium. Most strains could grow on the medium containing 600 mM NaCl, such as Bacillus zanthoxyli and Bacillus altitudinis. Furthermore, Bacillus zanthoxyli and Bacillus altitudinis were inoculated with tall fescue seeds and seedlings to determine their growth-promoting effect. The results showed that Bacillus altitudinis and mixed culture significantly increased the germination rate of tall fescue seeds. Bacillus zanthoxyli can significantly increase the tillers number and leaf width of seedlings under salt conditions. Through the synergistic effect of FaSOS1, FaHKT1, and FaHAK1 genes, Bacillus zanthoxyli helps to expel the excess Na⁺ from aboveground parts and absorb more K⁺ in roots to maintain ion homeostasis in tall fescue. Unexpectedly, we found that Bacillus altitudinis displayed an inapparent growth-promoting effect on seedlings under salt stress. Interestingly, the mixed culture of the two strains was also able to alleviate, to some extent, the effects of salt stress on tall fescue. This study provides a preliminary understanding of tall fescue rhizobacteria and highlights the role of Bacillus zanthoxyli in tall fescue growth and salt tolerance.

RNA sequencing-based exploration of the effects of blue laser irradiation on mRNAs involved in functional metabolites of D. officinales

Dendrobium officinale Kimura et Migo (D. officinale) has promising lung moisturizing, detoxifying, and immune boosting properties. Light is an important factor influencing functional metabolite synthesis in D. officinale. The mechanisms by which lasers affect plants are different from those of ordinary light sources; lasers can effectively address the shortcomings of ordinary light sources and have significant interactions with plants. Different light treatments (white, blue, blue laser) were applied, and the number of red leaves under blue laser was greater than that under blue and white light. RNA-seq technology was used to analyze differences in D. officinale under different light treatments. The results showed 465, 2,107 and 1,453 differentially expressed genes (DEGs) in LB-B, LB-W and W-B, respectively. GO, KEGG and other analyses of DEGs indicated that D. officinale has multiple blue laser response modes. Among them, the plasma membrane, cutin, suberine and wax biosynthesis, flavone and flavonol biosynthesis, heat shock proteins, etc. play central roles. Physiological and biochemical results verified that blue laser irradiation significantly increases POD, SOD, and PAL activities in D. officinale. The functional metabolite results showed that blue laser had the greatest promoting effect on total flavonoids, polysaccharides, and alkaloids. qPCR verification combined with other results suggested that CRY DASH, SPA1, HY5, and PIF4 in the blue laser signal transduction pathway affect functional metabolite accumulation in D. officinale through positively regulated expression patterns, while CO16 and MYC2 exhibit negatively regulated expression patterns. These findings provide new ideas for the efficient production of metabolites in D. officinale.

Responses of He-Ne laser on agronomic traits and the crosstalk between UVR8 signaling and phytochrome B signaling pathway in Arabidopsis thaliana subjected to supplementary ultraviolet-B (UV-B) stress

UV-B acclimation effects and UV-B damage repair induced by a 632.8-nm He-Ne laser were investigated in Arabidopsis thaliana plants in response to supplementary UV-B stress. There was an increasing trend in growth parameters in the combination-treated plants with He-Ne laser and UV-B light compared to those stressed with enhanced UV-B light alone during different developmental stages of plants. The photosynthetic efficiency (Pn) and survival rates of seedlings were significantly higher in the combination treatments than UV-B stress alone. The expression of UVR8, phytochrome B (PhyB), and their mediated signal responsive genes such as COP1, HY5, and CHS were also significantly upregulated in plants with the laser irradiation compared with other groups without the laser. Levels of flavonol accumulation in leaves and capsule yield of He-Ne laser-treated plants were increased. The phyB-9 mutants were more sensitive to enhanced UV-B stress and had no obvious improvements in plant phenotypic development and physiological damage caused by enhanced UV-B stress after He-Ne laser irradiation. Our results suggested that UVR8 and its mediated signaling pathway via interaction with COP1 can be induced by He-Ne laser, and these processes were dependent on cytoplasmic PhyB levels in plant cells, which might be one of the most important mechanisms of He-Ne laser on UV-B protection and UV-B damage repair. These current data have also elucidated that the biostimulatory effects of He-Ne laser on Arabidopsis thaliana plants would happen not only during the early growth stage but also during the entire late developmental stage.

A combination of He-Ne laser irradiation and exogenous NO application efficiently protect wheat seedling from oxidative stress caused by elevated UV-B stress

The elevated ultraviolet-B (UV-B) stress induces the accumulation of a variety of intracellular reactive oxygen species (ROS), which seems to cause oxidative stress for plants. To date, very little work has been done to evaluate the biological effects of a combined treatment with He-Ne laser irradiation and exogenous nitric oxide (NO) application on oxidative stress resulting from UV-B radiation. Thus, our study investigated the effects of a combination with He-Ne laser irradiation and exogenous NO treatment on oxidative damages in wheat seedlings under elevated UV-B stress. Our data showed that the reductions in ROS levels, membrane damage parameters, while the increments in antioxidant contents and antioxidant enzyme activity caused by a combination with He-Ne laser and exogenous NO treatment were greater than those of each individual treatment. Furthermore, these treatments had a similar effect on transcriptional activities of plant antioxidant enzymes. This implied that the protective effects of a combination with He-Ne laser irradiation and exogenous NO treatment on oxidative stress resulting from UV-B radiation was more efficient than each individual treatment with He-Ne laser or NO molecule. Our findings might provide beneficial theoretical references for identifying some effective new pathways for plant UV-B protection.

Proteomic and Metabolomic Analyses of Leaf from Clematis terniflora DC. Exposed to High-Level Ultraviolet-B Irradiation with Dark Treatment

Clematis terniflora DC. has potential pharmaceutical value; on the contrary, high-level UV-B irradiation with dark treatment led to the accumulation of secondary metabolites. Metabolomic and proteomic analyses of leaf of C. terniflora were performed to investigate the systematic response mechanisms to high-level UV-B irradiation with dark treatment. Metabolites related to carbohydrates, fatty acids, and amino acids and/or proteins related to stress, cell wall, and amino acid metabolism were gradually increased in response to high-level UV-B irradiation with dark treatment. On the basis of cluster analysis and mapping of proteins related to amino acid metabolism, the abundances of S-adenosylmethionine synthetase and cysteine synthase as well as 1,1-diphenyl-2-picrylhydrazyl scavenging activity were gradually increased in response to high-level UV-B irradiation with dark treatment. Furthermore, the abundance of dihydrolipoyl dehydrogenase/glutamate dehydrogenase and the content of γ-aminobutyric acid were also increased following high-level UV-B irradiation with dark treatment. Taken together, these results suggest that high-level UV-B irradiation with dark treatment induces the activation of reactive oxygen species scavenging system and γ-aminobutyric acid shunt pathway in leaf of C. terniflora.

Endogenous nitric oxide mediates He-Ne laser-induced adaptive responses in salt stressed-tall fescue leaves

The aim of this study was to investigate the role of endogenous nitric oxide in protective effects of He-Ne laser on salt stressed-tall fescue leaves. Salt stress resulted in significant increases of membrane injury, reactive oxygen species (ROS) production, polyamine accumulation, and activities of SOD, POD, and APX, while pronounced decreases of antioxidant contents, CAT activity and intracellular Ca(2+) concentration in seedlings leaves. He-Ne laser illumination caused a distinct alleviation of cellular injury that was reflected by the lower MDA amounts, polyamine accumulation and ROS levels at the stress period. In contrast, the laser treatment displayed a higher Ca(2+) concentration, antioxidant amounts, NO release, antioxidant enzyme, and NOS activities. These responses could be blocked due to the inhibition of NO biosynthesis by PTIO (NO scavenger) or LNNA (NOS inhibitor). The presented results demonstrated that endogenous NO might be involved in the progress of He-Ne laser-induced plant antioxidant system activation and ROS degradation in order to enhance adaptive responses of tall fescue to prolonged saline conditions.