Lactoferrin-derived resistance against plant pathogens in transgenic plants

Isolation, Characterization and Antibacterial Activity of 4-Allylbenzene-1,2-diol from Piper austrosinense

Isolation for antibacterial compounds from natural plants is a promising approach to develop new pesticides. In this study, two compounds were obtained from the Chinese endemic plant Piper austrosinense using bioassay-guided fractionation. Based on analyses of ¹H-NMR, ¹³C-NMR, and mass spectral data, the isolated compounds were identified as 4-allylbenzene-1,2-diol and (S)-4-allyl-5-(1-(3,4-dihydroxyphenyl)allyl)benzene-1,2-diol. 4-Allylbenzene-1,2-diol was shown to have strong antibacterial activity against four plant pathogens, including Xanthomonas oryzae pathovar oryzae (Xoo), X. axonopodis pv. citri (Xac), X. oryzae pv. oryzicola (Xoc) and X. campestris pv. mangiferaeindicae (Xcm). Further bioassay results exhibited that 4-allylbenzene-1,2-diol had a broad antibacterial spectrum, including Xoo, Xac, Xoc, Xcm, X. fragariae (Xf), X. campestris pv. campestris (Xcc), Pectobacterium carotovorum subspecies brasiliense (Pcb) and P. carotovorum subsp. carotovorum (Pcc), with minimum inhibitory concentration (MIC) values ranging from 333.75 to 1335 μmol/L. The pot experiment showed that 4-allylbenzene-1,2-diol exerted an excellent protective effect against Xoo, with a controlled efficacy reaching 72.73% at 4 MIC, which was superior to the positive control kasugamycin (53.03%) at 4 MIC. Further results demonstrated that the 4-allylbenzene-1,2-diol damaged the integrity of the cell membrane and increased cell membrane permeability. In addition, 4-allylbenzene-1,2-diol also prevented the pathogenicity-related biofilm formation in Xoo, thus limiting the movement of Xoo and reducing the production of extracellular polysaccharides (EPS) in Xoo. These findings suggest the value of 4-allylbenzene-1,2-diol and P. austrosinense could be as promising resources for developing novel antibacterial agents.

Lactoferrin and its role in biotechnological strategies for plant defense against pathogens

Agricultural crops are susceptible to many diseases caused by various pathogens, such as viruses, bacteria and fungi. This paper reviews the general principles of plant protection against pathogens, as well as the role of iron and antimicrobial peptide metabolism in plant immunity. The article highlights the principles of antibacterial, fungicidal and antiviral action of lactoferrin, a mammalian secretory glycoprotein, and lactoferrin peptides, and their role in protecting plants from phytopathogens. This review offers a comprehensive analysis and shows potential prospects of using the lactoferrin gene to enhance plant resistance to various phytopathogens, as well as the advantages of this biotechnological approach over existing methods of protecting plants against various diseases.

Transgenic Improvement for Biotic Resistance of Crops

Biotic constraints, including pathogenic fungi, viruses and bacteria, herbivory insects, as well as parasitic nematodes, cause significant yield loss and quality deterioration of crops. The effect of conventional management of these biotic constraints is limited. The advances in transgenic technologies provide a direct and directional approach to improve crops for biotic resistance. More than a hundred transgenic events and hundreds of cultivars resistant to herbivory insects, pathogenic viruses, and fungi have been developed by the heterologous expression of exogenous genes and RNAi, authorized for cultivation and market, and resulted in a significant reduction in yield loss and quality deterioration. However, the exploration of transgenic improvement for resistance to bacteria and nematodes by overexpression of endogenous genes and RNAi remains at the testing stage. Recent advances in RNAi and CRISPR/Cas technologies open up possibilities to improve the resistance of crops to pathogenic bacteria and plant parasitic nematodes, as well as other biotic constraints.

Novel piperazine-tailored ursolic acid hybrids as significant antibacterial agents targeting phytopathogens Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri probably directed by activation of apoptosis

BACKGROUND

Induced apoptosis is an effective technique that can reprogram cellular physiological and pathological processes to eradicate undesirable cells using their innate systems. Inspired by this, numerous apoptosis inducers have been developed to treat animal diseases, especially in the anticancer field. However, few studies have reported on the development of inductive agents that attack plant pathogens by activation of apoptosis. With the aim of exploring and discovering apoptosis inducers that target phytopathogens, a cluster of piperazine-tailored ursolic acid (UA) hybrids was systematically fabricated.

RESULTS

In vitro testing showed that the title molecules could inhibit the growth of two intractable bacterial strains, defined as Xanthomonas oryzae pv. oryzae and X. axonopodis pv. citri. The corresponding lowest EC50 values were 0.37 and 1.08 μg mL-1 , which exceed those of UA (>400 μg mL-1 ) and positive controls. Moreover, compounds 5u and 5v could manage bacterial blight in vivo using pot experiments. Flow cytometer analysis indicted that the title compounds could induce distinct apoptotic behaviors on tested bacteria. In-depth study revealed that the introduction of designed compounds could reduce the enzyme activities of catalase and superoxide dismutase, subsequently leading to the accumulation of reactive oxygen species.

CONCLUSION

This study promoted the development of apoptosis initiators for managing bacterial infections in agriculture by an innovative mode of action. © 2020 Society of Chemical Industry.

Improving Expression of Bovine Lactoferrin N-Lobe by Promoter Optimization and Codon Engineering in Bacillus subtilis and Its Antibacterial Activity

Bovine lactoferrin N-lobe plays an important key in the nonimmunological defense system. In this work, the most suitable promoter P_veg was selected and the fragment coding bovine lactoferrin N-lobe was optimized according to codon bias of Bacillus. The recombinant plasmid pMA0911-P_veg-mBLF-N was introduced into Baicillus subtilis 168 to create B. subtilis/pMA0911-P_veg-mBLF-N. The bovine lactoferrin N-lobe was highly expressed at 28 °C for 15 h. Its purified protein was obtained with 16.5 mg/L and a purity of 93.6% using ammonium sulfate precipitation, Ni-NTA, and molecular exclusion. About 200 ng/mL purified bovine lactoferrin N-lobe completely inhibited cell-growth of Escherichia coli JM109 (DE3), 70.3% of Pseudomonas aeruginosa CGMCC 1.6740, and 41.5% of Staphylococcus aureus CGMCC 1.282. To our knowledge, this is the first report about active expression, purification, and characterization of bovine lactoferrin N-lobe in safe bacterium B. subtilis, which opens an available application way in the biomedical and food industries.

A silkworm based silk gland bioreactor for high-efficiency production of recombinant human lactoferrin with antibacterial and anti-inflammatory activities

Background

Silk glands are used by silkworms to spin silk fibers for making their cocoons. These have recently been regarded as bioreactor hosts for the cost-effective production of other valuable exogenous proteins and have drawn wide attention.

Results

In this study, we established a transgenic silkworm strain which synthesizes the recombinant human lactoferrin (rhLF) in the silk gland and spins them into the cocoon by our previously constructed silk gland based bioreactor system. The yield of the rhLF with the highest expression level was estimated to be 12.07 mg/g cocoon shell weight produced by the transgenic silkworm strain 34. Utilizing a simple purification protocol, 9.24 mg of the rhLF with recovery of 76.55% and purity of 95.45% on average could be purified from 1 g of the cocoons. The purified rhLF was detected with a secondary structure similar with the commercially purchased human lactoferrin. Eight types of N-glycans which dominated by the GlcNAc (4) Man (3) (61.15%) and the GlcNAc (3) Man (3) (17.98%) were identified at the three typical N-glycosylation sites of the rhLF. Biological activities assays showed the significant evidence that the purified rhLF could relief the lipopolysaccharide (LPS)-induced cell inflammation in RAW264.7 cells and exhibit potent antibacterial bioactivities against the Escherichia coli (E. coli) and Bacillus subtilis.

Conclusions

These results show that the middle silk gland of silkworm can be an efficient bioreactor for the mass production of rhLF and the potential application in anti-inflammation and antibacterial.

Electronic supplementary material

The online version of this article (10.1186/s13036-019-0186-z) contains supplementary material, which is available to authorized users.

Antimicrobial peptide melittin against Xanthomonas oryzae pv. oryzae, the bacterial leaf blight pathogen in rice

Xanthomonas oryzae pv. oryzae is a destructive bacterial disease of rice, and the development of an environmentally safe bactericide is urgently needed. Antimicrobial peptides, as antibacterial sources, may play important roles in bactericide development. In the present study, we found that the antimicrobial peptide melittin had the desired antibacterial activity against X. oryzae pv. oryzae. The antibacterial mechanism was investigated by examining its effects on cell membranes, energy metabolism, and nucleic acid, and protein synthesis. The antibacterial effects arose from its ability to interact with the bacterial cell wall and disrupt the cytoplasmic membrane by making holes and channels, resulting in the leakage of the cytoplasmic content. Additionally, melittin is able to permeabilize bacterial membranes and reach the cytoplasm, indicating that there are multiple mechanisms of antimicrobial action. DNA/RNA binding assay suggests that melittin may inhibit macromolecular biosynthesis by binding intracellular targets, such as DNA or RNA, and that those two modes eventually lead to bacterial cell death. Melittin can inhibit X. oryzae pv. oryzae from spreading, alleviating the disease symptoms, which indicated that melittin may have potential applications in plant protection.

Tissue-specific and pathogen-inducible expression of a fusion protein containing a Fusarium-specific antibody and a fungal chitinase protects wheat against Fusarium pathogens and mycotoxins

Fusarium head blight (FHB) in wheat and other small grain cereals is a globally devastating disease caused by toxigenic Fusarium pathogens. Controlling FHB is a challenge because germplasm that is naturally resistant against these pathogens is inadequate. Current control measures rely on fungicides. Here, an antibody fusion comprised of the Fusarium spp.-specific recombinant antibody gene CWP2 derived from chicken, and the endochitinase gene Ech42 from the biocontrol fungus Trichoderma atroviride was introduced into the elite wheat cultivar Zhengmai9023 by particle bombardment. Expression of this fusion gene was regulated by the lemma/palea-specific promoter Lem2 derived from barley; its expression was confirmed as lemma/palea-specific in transgenic wheat. Single-floret inoculation of independent transgenic wheat lines of the T3 to T6 generations revealed significant resistance (type II) to fungal spreading, and natural infection assays in the field showed significant resistance (type I) to initial infection. Gas chromatography-mass spectrometry analysis revealed marked reduction of mycotoxins in the grains of the transgenic wheat lines. Progenies of crosses between the transgenic lines and the FHB-susceptible cultivar Huamai13 also showed significantly enhanced FHB resistance. Quantitative real-time PCR analysis revealed that the tissue-specific expression of the antibody fusion was induced by salicylic acid drenching and induced to a greater extent by F. graminearum infection. Histochemical analysis showed substantial restriction of mycelial growth in the lemma tissues of the transgenic plants. Thus, the combined tissue-specific and pathogen-inducible expression of this Fusarium-specific antibody fusion can effectively protect wheat against Fusarium pathogens and reduce mycotoxin content in grain.