Plants interact with microbial polysaccharides

Process and applications of alginate oligosaccharides with emphasis on health beneficial perspectives

Alginates are linear polymers comprising 40% of the dry weight of algae possess various applications in food and biomedical industries. Alginate oligosaccharides (AOS), a degradation product of alginate, is now gaining much attention for their beneficial role in food, pharmaceutical and agricultural industries. Hence this review was aimed to compile the information on alginate and AOS (prepared from seaweeds) during 1994-2020. As per our knowledge, this is the first review on the potential use of alginate oligosaccharides in different fields. The alginate derivatives are grouped according to their applications. They are involved in the isolation process and show antimicrobial, antioxidant, anti-inflammatory, antihypertension, anticancer, and immunostimulatory properties. AOS also have significant applications in prebiotics, nutritional supplements, plant growth development and others products.

Characterization of the Medicago truncatula cell wall proteome in cell suspension culture upon elicitation and suppression of plant defense

In addition to establishing methods for proteome analysis of cell wall proteins (CWPs) for the model plant Medicago truncatula, this work highlights the presence of several protein classes in cell culture. Using a combination of two-dimensional gel electrophoresis (2D-PAGE) and/or liquid chromatography-tandem mass spectrometry (LC-MS/MS), we established the proteome reference map of M. truncatula cell wall proteins. CWPs extracted from purified cell wall fragments resulted in the identification of 46 (2D-PAGE) and 65 (LC-MS/MS) proteins, respectively, with a total of 111 proteins. The identified proteins are involved in various processes, including cell wall modifications, signaling, defense mechanisms, membrane transport, protein synthesis and processing. Further, we conducted comparative proteome analysis to identify changes in protein composition during interaction of M. truncatula cell suspension culture with a pathogen-derived yeast elicitor (YE) and suppressor using Sinorhizobium meliloti LPS. 2D-PAGE analysis for the CWPs after YE and LPS treatment resembled the proteome map of YE alone, with a few up-regulated proteins involved in defense, and in the case of the LPS-treated cell wall proteome, there was no significant difference observed. Using this approach, proteins involved in defense, such as l-ascorbate peroxidase, specifically targeted proteins to the cell wall during defense, including glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and proteins that play an important role during growth and development were identified. Also, some defense-related proteins were absent in the same gel after YE treatment, suggesting that oxidant protection is regulated by these proteins.

Quantitative PCR study on the mode of action of oligosaccharide elicitors on penicillin G production by Penicillium chrysogenum

AIM

To investigate the effects of single and multiple additions of the oligosaccharide elicitors, obtained from alginate and locust bean gum, on penicillin G production and the transcript level of penicillin G biosynthetic genes.

METHODS AND RESULTS

The transcript copy numbers and penicillin G concentration in liquid cultures of Penicillium chrysogenum grown under control and elicited conditions were compared using quantitative PCR and HPLC assay respectively. An increase in the penicillin G production rate and transcript copy numbers of the three major penicillin G biosynthetic genes pcbAB, pcbC and penDE was observed in the elicited cultures compared to control cultures. The effects were observed to be higher in multiple elicitor added cultures compared to single elicitor supplemented and control cultures.

CONCLUSIONS

The results show, for the first time in bioreactor cultures, the enhancement of penicillin G transcript copy number of the penicillin biosynthetic genes using qPCR with a corresponding increase in the penicillin G production upon multiple elicitor addition of two different types of elicitors.

SIGNIFICANCE AND IMPACT OF THE STUDY

Establishment of the effect of multiple elicitor addition on penicillin G production and investigating the role of oligosaccharide elicitors as transcriptional activators has wide spread impact for antibiotic industry.

Growth-phase-dependent immunodeterminants of Rhizobium trifolii lipopolysaccharide which bind trifoliin A, a white clover lectin

The lipopolysaccharide (LPS) from Rhizobium trifolii 0403 was isolated at different stages of growth and was examined for its (i) ability to bind a white clover lectin (trifoliin A), (ii) immunochemical properties, and (iii) composition. There was significantly more binding of trifoliin A to purified LPS and cells in the early stationary phase than to cells in the exponential phase. Immunofluorescence and enzyme-linked immunosorbent assays indicated that new antigenic determinants of the LPS appeared for brief periods on cells at the end of the lag phase and again at the beginning of the stationary phase. These new antigens were not detected on cells in midexponential or late stationary phase. Monovalent fragments of immunoglobulin G antibodies raised against the unique antigenic determinants in the LPS competitively blocked the binding of trifoliin A to cells in the early stationary phase. Gas chromatographic analysis showed that the relative quantity of several glycosyl components in the LPS increased as the culture advanced from the midexponential to the early stationary phase. In addition, LPS from cells in the early stationary phase had a higher aggregate molecular weight. Quinovosamine (2-amino-2,6-dideoxyglucose) was identified by combined gas chromatography-mass spectrometry as a sugar component of the LPS which had not been previously reported. D-Quinovosamine, N-acetyl-D-quinovosamine, and its n-propyl-beta-glycoside were effective hapten sugars which inhibited the binding of trifoliin A, anti-clover root antibody, and homologous antibody to these new determinants in the LPS. White clover plants had more infected root hairs after incubation with an inoculum of cells in the early stationary phase than after incubation with cells in the midexponential phase. The profound influence of the growth phase on the composition of lectin-binding polysaccharides of Rhizobium may be a major underlying cause of conflicting data among laboratories testing the lectin-recognition hypothesis. In addition, these chemical modifications may reflect mechanisms which regulate Rhizobium-root hair recognition in this nitrogen-fixing symbiosis.

Agglutination of Plant Protoplasts by Fungal Cell Wall Glucans

Glucans, called elicitors, isolated from cell walls of Phytophthora infestans, caused rapid agglutination and death of protoplasts isolated from potato leaf tissue. Cells incubated with high concentrations of elicitor were rapidly killed, but did not agglutinate. Agglutination and cell death did not occur with any of several commercial polysaccharides including laminarin, but laminarin did inhibit elicitor-mediated agglutination. The results are consistent with the existence of specific elicitor receptor sites on the outer surface of potato leaf plasma membranes.