Proteomics-based identification of orchid-associated bacteria colonizing the Epipactis albensis, E. helleborine and E. purpurata (Orchidaceae, Neottieae)

Amalgamation of Metal Tolerant PGPR Buttiauxella sp. EA20 with Birch Wood Biochar Enhanced Growth and Biofortification of Rapeseed under Copper Action

BACKGROUND

Amalgamation of metal-tolerant plant growth promoting rhizobacteria (PGPR) with biochar is a promising direction for the development of chemical-free biofertilizers that can mitigate environmental risks, enhance crop productivity and their biological value. The main objective of the work includes the evaluation of the influence of prepared bacterial biofertilizer (BF) on biometric growth parameters as well as physiological and biochemical characteristics of rapeseed (Brassica napus L.) at copper action.

METHODS

The prepared BF was based on novel metal tolerant strain of PGPR Buttiauxella sp. EA20 isolated from the rhizosphere of orchid Epipactis atrorubens and birch wood biochar (BC). The pot-scale experiments included six treatments: peat-containing control substrate (CS); CS + 200Cu (200 mg Cu/kg of soil); CS + 5% BC (v/v); CS + 5% BC + 200Cu; CS + 5% BF (v/v); CS + 5% BF + 200Cu.

RESULTS

Single Cu treatment caused the decrease in rapeseed leaf area, shoot and root length, fresh and dry biomass, as well as an increase in water saturation deficit, possibly due to damage of cell membranes by lipid peroxidation. Addition of BF or BC alone mitigated these harmful effects of copper. Application of BF, regardless of Cu addition, increased the rapeseed leaf area (1.6 times on average), plant fresh and dry biomass (2.5 times on average), and photosynthetic pigment content (1.8 times on average). In addition, BF treatment along with Cu enhanced the antioxidant activity of B. napus due to the accumulation of non-enzymatic antioxidants such as carotenoids, free proline and soluble phenolic compounds, including flavonoids. Moreover, plant enrichment with copper and essential macronutrients such as nitrogen, phosphorus and potassium was observed.

CONCLUSIONS

The study concludes that application of complex biofertilizer based on metal tolerant PGPR strain Buttiauxella sp. EA20 and birch wood biochar mitigated the harmful effects of copper, enhanced the rapeseed growth and increased its biological value. Future perspective includes evaluation of the potential for using the resulting biofertilizer to improve the growth and biofortification of other crop species.

Phleum pratense-pollen adaptive variations and pollen microbiome investigation under different climatic regions and prospects of allergenicity

Phleum pratense is an allergenic grass that pollinates in spring in Pakistan. Databases Allergenonline.org and Allergen.org record ten P. pratense allergens and their isoforms. Phl P 1, Phlp 5, and Phl p 11 are major P. pratense-pollen allergens with demonstrated basophil activity and skin test reactivity. Little is known about P. pratense pollen adaptive variations in different climatic regions and pollen-associated microbial diversity. In this study, we collected P. pratense-pollen and soils in the spring season 2022. Samples were collected from three climatic regions in Pakistan (R1, R2 and R3) with differences in mean monthly air temperature, mean monthly precipitation and elevation. The morphology of pollen was observed by light microscopy, scanning electron microscopy (SEM), biochemical fingerprint analysis, and composition of pollen were investigated by fourier-transform infrared spectroscopy (FTIR). The pollen-associated bacterial populations were identified through a Biolog GEN III microplate system. The pollen water-soluble proteins were isolated and stabilized in phosphate buffer saline (PBS) and tested for allergenicity responses through dot blots and western blots analysis. The morphology study found difference in pollen biochemical composition. Biolog identified Brevibacterium epidermidis and Pantoea agglomerans from P. pratense pollen. Protein extract quantification and sodium dodecyl sulfate-poly acrylamide gel electrophoresis (SDS-PAGE) gel found decreased protein expression in R1 region pollen compared to R2 and R3 region pollen. Allergenicity studies found differential expression of beta-expansin and profilin allergens in pollen obtained from the three regions. Beta-expansin and profilin were suppressed in R1 pollen and expressed in compared to R2 and R3 pollen. This is the first study to identify B. epidermidis and P. agglomerans growth on P. pratense pollen. Variable allergen expression in P. pratense pollen has also been observed in different regions. Soil pH, an increase in mean monthly temperature and a decrease in mean monthly precipitation correlated with pollen biochemical composition, and reduced beta-expansin and profilin expression involved in pollen growth and development. The findings of this research are unique, which enhances basic knowledge and understanding of P. pratense-pollen associated microbiota and climate change impacts on the pollen allergen expression.

Phosphorylation of 399S at CsHsp70 of Cymbidium sinense is essential to maintain chlorophyll stability

The Chinese orchids symbolise nobility and gentility in China, and the variation of leaf color makes Cymbidium sinense more diversified and valuable. However, its color variations especially at the protein level still remain largely unexplored. In this study, the proteomics and phosphoproteomics of Cymbidium sinense leaf color variation mutants were studied. A total of 1059 differentially abundant proteins (DAPs) and 1127 differentially abundant phosphorylation sites belonging to 644 phosphoproteins (DAPPs) were identified in the yellow section of leaf variegation mutant of Cymbidium sinense (MY) compared with the green section (MG). Moreover, 349 co-expressing proteins were found in both omics' datasets, while only 26 proteins showed the same expression patterns in the two omics. The interaction network analysis of kinases and phosphatases showed that DAPs and DAPPs in photosynthesis, response to hormones, pigment metabolic process, phosphorylation, glucose metabolic process, and dephosphorylation might contribute to leaf color variation. The abundance of 28 Hsps and 28 phosphorylation sites belonging to 10 Hsps showed significant differences between MG and MY. CsHsp70 was selected to explore the function in Cymbidium sinense leaf variegation. The results showed CsHsp70 is essential for maintaining photosynthetic pigment content and the 399S phosphorylation site is crucial to the function of CsHsp70. Collectively, our findings construct a comprehensive coverage of protein and protein phosphorylation in leaf variegation of C. sinense, providing valuable insights into its formation mechanisms.

Stigmas of holoparasitic Phelipanche arenaria (Orobanchaceae) - a suitable ephemeric flower habitat for development unique microbiome

BACKGROUND

Microbial communities have occasionally been observed in part of the ephemeric reproductive structure of floral stigmas, but their prevalence, phylogenetic diversity and ecological roles are understudied. This report describes the first study of bacterial and fungal communities in immature and mature stigma tissue of the endangered holoparasitic plant Phelipanche arenaria. Culture-dependent methods coupled with next-generation sequencing indicated that a small surface of the flower stigma was an unexpectedly rich and diverse microhabitat for colonization of microbial. We also compared the enzymatic activity of the bacterial communities between immature and mature stigmas samples.

RESULTS

Using high-throughput sequencing methods, we identified and classified 39 to over 51 OTUs per sample for bacterial OTUs represented by Pantoea agglomerans and P. ananatis, comprising 50.6%, followed by Pseudomonas, Luteibacter spp., Sphingomonas spp. with 17% of total frequency. The bacterial profile of immature stigmas of P. arenaria contained unique microorganisms (21 of the most numerous OTUs) that were not confirmed in mature stigmas. However, the enzymatic activity of bacteria in mature stigmas of P. arenaria showed more activity than observed in immature stigmas. In the fungal profile, we recorded even 80 OTUs in mature stigmas, consisting of Capnodiales 45.03% of the total abundance with 28.27% of frequency was created by Alternaria eichhorniae (10.55%), Mycosphaerella tassiana (9.69%), and Aureobasidium pullulans (8.03%). Additionally, numerous putative plant growth-promoting bacteria, fungal pathogens and pathogen-antagonistic yeasts were also detected.

CONCLUSIONS

Our study uncovered that P. arenaria stigmas host diverse bacterial and fungal communities. These microorganisms are well known and have been described as beneficial for biotechnological and environmental applications (e.g., production of different enzymes and antimicrobial compounds). This research provided valuable insight into the parasitic plant-microbe interactions.

Auxin biosynthesis by Microbacterium testaceum Y411 associated with orchid aerial roots and their efficacy in micropropagation

Root-associated bacteria strongly affect plant growth and development by synthesizing growth regulators and stress-relieving metabolites. The present study is mainly focused on assessing aerial root-associated bacteria of Rhynchostylis retusa (L.) Blume is an endemic epiphytic orchid responsible for auxin production and influencing plant growth. A bacterial isolate, Microbacterium testaceum Y411, was found to be the most active producer of indole-3-acetic acid (IAA). The maximum IAA production (170µg/mL) was recorded with the bacterium at optimum process parameters such as pH 7, temperature 30°C, and tryptophan 1000 µg/mL in a culture medium for 48 h. The extracted auxin was purified and analyzed by FT-IR, HPLC, and HR-MS, indicating bacterial auxin has a similar mass value to 4-chloroindole-3-acetic acid auxin. Furthermore, the bacterial auxin was tested on in vitro propagation of orchid, Cymbidium aloifolium, and 90% seed germination was recorded in Murashige and Skoog's medium supplemented with bacterial auxin. The novel results obtained in this study are used for agricultural applications and the Microbacterium testaceum Y411 is a valuable biotechnological resource for a natural auxin.

Rhizobium rhizogenes infection in threatened Indian orchid Dendrobium ovatum mobilises 'Moscatilin' to enhance plant defensins

The present study illustrates the transformation ability of two wild-type bacterial strains of Rhizobium rhizogenes (MTCC 532 and MTCC 2364) on the embryogenic callus and callus-derived plantlets of a threatened Indian orchid, Dendrobium ovatum. Co-culture of the bacterium with the explants gave marginal hairy root phenotype that failed to multiply in the culture medium. Some primary and secondary metabolites were subdued in infected explants. Moscatilin, the stilbenoid active principle in D. ovatum, was found below the detection limit. The presence of two metabolites viz., Laudanosine, a benzyltetrahydroisoquinoline alkaloid and Lyciumin B, a cyclic peptide, were detected exclusively in the infected explants. The subjugated amino acids and phenolics in the infected plantlets were routed to produce phytoanticipins, and phenanthrenes, strengthening the defence mechanism in infected tissues. This research implies that the plant's defence mechanism activation could have prevented the extensive hairy root formation in the explants, even though nodulations and phenotype transitions were witnessed. Moscatilin has a structural resemblance with Resveratrol, a phytoalexin that combats bacterial and fungal pathogens. The study favours the possibility of Moscatlin being a precursor for phenanthrene compounds, thereby serving as a 'phytoanticipin' during the infection phase.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03180-9.