Efficiency of the alpha-hairpinin SmAMP-X gene promoter from Stellaria media plant depends on selection of transgenic approach

The antimicrobial activity of the alpha-HAIRPININ ANTIMICROBIAL PEPTIDE X (SmAMP-X gene, GenBank acc. No. HG423454.1) from Stellaria media plant has been shown in vitro. Here, we isolated the SmAMP-X gene promoter and found two genomic sequences for the promoter (designated pro-SmAMP-X and pro-SmAMP-X-Ψ2) with 83% identity in their core and proximal regions. We found that the abilities of these promoters to express the uidA reporter and the nptII selectable marker differ according to the structural organization of T-DNA in the binary vector used for plant transformation. Analysis of Agrobacterium-infiltrated Nicotiana benthamiana leaves, transgenic Arabidopsis thaliana lines, and transgenic Solanum tuberosum plants revealed that both promoters in the pCambia1381Z and pCambia2301 binary vectors generate 42-100% of the ß-glucuronidase (GUS) activity generated by the CaMV35S promoter. According to 5'-RACE (rapid amplification of cDNA ends) analysis, both plant promoters are influenced by the CaMV35S enhancer used to express selectable markers in the T-DNA region of pCambia1381Z and pCambia2301. The exclusion of CaMV35S enhancer from the T-DNA region significantly reduces the efficiency of pro-SmAMP-X-Ψ2 promoter for GUS production. Both promoters in the pCambia2300 vector without CaMV35S enhancer in the T-DNA region weakly express the nptII selectable marker in different tissues of transgenic N. tabacum plants and enable selection of transgenic cells in media with a high concentration of kanamycin. Overall, promoter sequences must be functionally validated in binary vectors lacking CaMV35S enhancer.

Development of potato (Solanum tuberosum L.) plants with StLEAFY knockout

StLFY-knockout potato plants were developed using CRISPR/Cas9 system. Inflorescences of edited plants transited to flowering, but inflorescence structures lacked flowers and were indeterminate, producing multiple shoot meristems. The tetraploid potato (Solanum tuberosum L.) is an important agricultural crop worldwide. In this study, we used CRISPR/Cas9 to inactivate the potato homolog (StLFY) of the LEAFY gene-a key regulator of the transition to flowering and floral meristem identity-in a tetraploid potato cultivar. We achieved high rates of all-allelic knockouts. Frameshift indels led to phenotypic alterations, including indeterminate inflorescence development and the replacement of flowers with the leafy-like structures.

Agrobacterium-mediated transformation of potato Solanum tuberosum L. with constructs carrying the strong plant-derived promoter pro-SmAMP1 from Stellaria media L

The effectiveness of plant genetic transformation is determined by the choice of genetic structures and their regulatory sequences that cause a high and stable expression level of heterologous genes. In this regard, the actual task of biotechnology is the use of highly effective plant promoters. The choice of promoter determines not only the level of the expression gene, but also the effectiveness of genetic transformation. The purpose of our study was to evaluate the influence of explant type and 5-deletion variants of the plant strong pro-SmAMP1 promoter, on the Agrobacterium -mediated transformation efficiency of potato ( Solanum tuberosum L.) cv. Udacha. To analyze the regenerative capacity of potato stem and leaf explants, AGL0 strain carrying constructs containing the 5-deletion variants of the promoter fragment of gene encoding antimicrobial peptide from Stellaria media L. ( pro-SmAMP1 ) was carried out. Four genetic constructs based on the plant expression vector pCAMBIA1381Z were used in this work, containing the selectable gene hptII and reporter gene uidA under different 5-deletion variants of the pro-SmAMP1 promoter (-442, -675, -732 and -1196 bp relative to the transcription initiation site); as well as two binary vectors based on the expression vector pCAMBIA1302 with 5-deletion pro-SmAMP1 promoter variants (-442 and -1196 bp), controlling the expression of gfp reporter gene. It was found that the effectiveness of Agrobacterium -mediated transformation depended on the type of genetic construction used, but not on the type of explant being cultivated. The insertion of the promoter region pro-SmAMP1 gene, hptII , as well as the absence of the bacterial Vir E gene was confirmed by PCR. Depending on the type of genetic construct, the transformation efficiency for the reporter gene varied from 2.0 to 7.2 %. The results are compared with previously conducted few studies, according to which the choice of promoter determines not only the expression level of marker genes, but also has a significant influence on the genetic transformation efficiency.

High Resistance of Potato to Early Blight Is Achieved by Expression of the Pro-SmAMP1 Gene for Hevein-Like Antimicrobial Peptides from Common Chickweed (Stellaria media)

In the common chickweed Stellaria media, two antimicrobial peptides (AMPs), SmAMP1.1a and SmAMP1.2a, have been shown to be proteolytically released as products of the expression of a single gene, proSmAMP1. In this study, the gene proSmAMP1 was introduced into two potato varieties, Zhukovsky ranny and Udacha. These early-maturing varieties were shown to be susceptible to early blight caused by Alternaria spp. Most transgenic lines of either variety having strong expression of the target gene demonstrated high levels of resistance to Alternaria spp. during three years of cultivation, but did not otherwise differ from the initial varieties. Disease severity index (DSI) was introduced as a complex measure of plant susceptibility to early blight, taking into account the diameter of lesions caused by the Alternaria spp., the fungus sporulation intensity and its incubation period duration. Across all transgenic lines, the DSI inversely correlated both with the target gene expression and the copy number in the plant genome. Our results are promising for improving the resistance of potato and other crops to early blight by expression of AMPs from wild plants.

Biotechnological Insights on the Expression and Production of Antimicrobial Peptides in Plants

The emergence of drug-resistant pathogens poses a serious critical threat to global public health and requires immediate action. Antimicrobial peptides (AMPs) are a class of short peptides ubiquitously found in all living forms, including plants, insects, mammals, microorganisms and play a significant role in host innate immune system. These peptides are considered as promising candidates to treat microbial infections due to its distinct advantages over conventional antibiotics. Given their potent broad spectrum of antimicrobial action, several AMPs are currently being evaluated in preclinical/clinical trials. However, large quantities of highly purified AMPs are vital for basic research and clinical settings which is still a major bottleneck hindering its application. This can be overcome by genetic engineering approaches to produce sufficient amount of diverse peptides in heterologous host systems. Recently plants are considered as potential alternatives to conventional protein production systems such as microbial and mammalian platforms due to their unique advantages such as rapidity, scalability and safety. In addition, AMPs can also be utilized for development of novel approaches for plant protection thereby increasing the crop yield. Hence, in order to provide a spotlight for the expression of AMP in plants for both clinical or agricultural use, the present review presents the importance of AMPs and efforts aimed at producing recombinant AMPs in plants for molecular farming and plant protection so far.

Synthesis and biological evaluation of stilbene-based peptoid mimics against the phytopathogenic bacterium Xanthomonas citri pv. citri

BACKGROUND

The emergence of drug-resistant phytopathogenic bacteria and the need for new types of biological disease-control agents have accelerated efforts toward searching for alternative candidates with a low propensity for resistance development. In this study, a new series of stilbene-based peptoid mimics were synthesized, and their biological activities were evaluated against citrus pathogenic bacteria in vitro and in vivo.

RESULTS

Antibacterial bioassay results showed that the dicationic peptoid mimics 9a and 9b displayed excellent bioactivity against Xanthomonas citri pv. citri, with the minimum inhibitory concentration values of 25 μM, which were superior to those of commercial copper biocides Delite (200 μM) and Kasumin Bordeaux (100 μM). In vivo bioassay further confirmed their control efficacy against plant bacterial diseases. In addition, the antibacterial mechanism of action elucidated their membrane-disruption effects resulting in the leakage of the bacterial membranes, which was similar to that of antimicrobial peptides. Moreover, the inhibition effect on biofilm formation of peptoid mimics has also been demonstrated.

CONCLUSION

Stilbene-based peptoid mimics synthesized in this study showed promising antibacterial activity with a potent membrane-disruptive mechanism. The results suggested that stilbene-based peptoid mimics have the potential as a candidate new type of bactericide for citrus disease protection.

Antimicrobial Peptides: Recent Insights on Biotechnological Interventions and Future Perspectives

With the unprecedented rise of drug-resistant pathogens, particularly antibiotic-resistant bacteria, and no new antibiotics in the pipeline over the last three decades, the issue of antimicrobial resistance has emerged as a critical public health threat. Antimicrobial Peptides (AMP) have garnered interest as a viable solution to this grave issue and are being explored for their potential antimicrobial applications. Given their low bioavailability in nature, tailoring new AMPs or strategizing approaches for increasing the yield of AMPs, therefore, becomes pertinent. The present review focuses on biotechnological interventions directed towards enhanced AMP synthesis and revisits existing genetic engineering and synthetic biology strategies for production of AMPs. This review further underscores the importance and potential applications of advanced gene editing technologies for the synthesis of novel AMPs in future.