High CO2 concentration as an inductor agent to drive production of recombinant phytotoxic antimicrobial peptides in plant biofactories

Elevated CO2 alters transgene methylation not only in promoterregion but also in codingregion of Bt rice under different N-fertilizer levels

The earth has been undergoing climate change, especially in recent years, driven by increasing concentration of atmospheric carbon dioxide (CO₂) and rising earth-surface temperature, which could reduce N allocation to Bt toxin for transgenic Bt crops (Bt crops), but the N fertilization is considered to be an effective method to enhance the C-N balance in Bt crops in the case of elevated CO₂ in future. DNA methylation not only in promoterregion but also in codingregion of transgene plays a critical role in transgene expression regulation and silencing of transgenic crops. Recent research has emphasized the risks of increased transgene silencing of Bacillus thuringiensis (Bt) rice under elevated CO₂. In this study, the effects of elevated CO₂ (vs. ambient CO₂) on exogenous Bt toxins and transgene expression in promoterregion and codingregion of Bt rice during tillering stage (cv. HH1 expressing fused Cry1Ab/Cry1Ac) were evaluated under three nitrogen (N) fertilizer rate (1/4, 1 and 2 N levels). The aboveground and belowground biomass, and foliar Bt protein content of Bt rice were all significantly increased with the augmentation of N-fertilizer. And elevated CO₂ significantly increased belowground biomass, total soluble protein content, transgene methylation levels in promoterregion (P1), and in total of promoterregion(P1) and codingregion (P2 + P3) (i.e., P1 + P2 + P3) at 1 N level, and it also increased transgene methylation levels in codingregion (P2), and in total of promoterregion and codingregion (P1 + P2 + P3) at 2 N level. In addition, elevated CO₂ decreased foliar Bt protein content at 1 N level. The transgene methylation levels in promoterregion and codingregion were negatively correlated with Bt-transgene expression level. The methylation level of cytosines located at CG sites was higher than those at CHG and CHH sites in P1, P2 and P3 fragments regardless of the CO₂ or N-fertilizer level. The correlation of transgene mehtylation in promoterregion with transgene expression is even stronger than that in codingregion. These data indicate that N fertilization supply will increase the Bt toxin content in transgenic Bt rice, especially under elevated CO₂.

Novel Rosaceae plant elicitor peptides as sustainable tools to control Xanthomonas arboricola pv. pruni in Prunus spp

Fruit crops are regarded as important health promoters and constitute a major part of global agricultural production, and Rosaceae species are of high economic impact. Their culture is threatened by bacterial diseases, whose control is based on preventative treatments using compounds of limited efficacy and negative environmental impact. One of the most economically relevant examples is the pathogen Xanthomonas arboricola pv. pruni (Xap) affecting Prunus spp. The plant immune response against pathogens can be triggered and amplified by plant elicitor peptides (Peps), perceived by specific receptors (PEPRs). Although they have been described in various angiosperms, scarce information is available on Rosaceae species. Here, we identified the Pep precursor (PROPEP), Pep and PEPR orthologues of 10 Rosaceae species and confirmed the presence of the Pep/PEPR system in this family. We showed the perception and elicitor activity of Rosaceae Peps using the Prunus-Xap pathosystem as proof-of-concept. Treatment with nanomolar doses of Peps induced the corresponding PROPEP and a set of defence-related genes in Prunus leaves, and enhanced resistance against Xap. Peps from the same species had the highest efficiencies. Rosaceae Peps could potentially be used to develop natural, targeted and environmentally friendly strategies to enhance the resistance of Prunus species against biotic attackers.

Impacts of elevated CO2 on exogenous Bacillus thuringiensis toxins and transgene expression in transgenic rice under different levels of nitrogen

Recent studies have highlighted great challenges of transgene silencing for transgenic plants facing climate change. In order to understand the impacts of elevated CO2 on exogenous Bacillus thuringiensis (Bt) toxins and transgene expression in transgenic rice under different levels of N-fertilizer supply, we investigated the biomass, exogenous Bt toxins, Bt-transgene expression and methylation status in Bt rice exposed to two levels of CO2 concentrations and nitrogen (N) supply (1/8, 1/4, 1/2, 1 and 2 N). It is elucidated that the increased levels of global atmospheric CO2 concentration will trigger up-regulation of Bt toxin expression in transgenic rice, especially with appropriate increase of N fertilizer supply, while, to some extent, the exogenous Bt-transgene expression is reduced at sub-N levels (1/4 and 1/2N), even though the total protein of plant tissues is reduced and the plant growth is restricted. The unpredictable and stochastic occurrence of transgene silencing and epigenetic alternations remains unresolved for most transgenic plants. It is expected that N fertilization supply may promote the expression of transgenic Bt toxin in transgenic Bt rice, particularly under elevated CO2.

Adding Functions to Biomaterial Surfaces through Protein Incorporation

The concept of biomaterials has evolved from one of inert mechanical supports with a long-term, biologically inactive role in the body into complex matrices that exhibit selective cell binding, promote proliferation and matrix production, and may ultimately become replaced by newly generated tissues in vivo. Functionalization of material surfaces with biomolecules is critical to their ability to evade immunorecognition, interact productively with surrounding tissues and extracellular matrix, and avoid bacterial colonization. Antibody molecules and their derived fragments are commonly immobilized on materials to mediate coating with specific cell types in fields such as stent endothelialization and drug delivery. The incorporation of growth factors into biomaterials has found application in promoting and accelerating bone formation in osteogenerative and related applications. Peptides and extracellular matrix proteins can impart biomolecule- and cell-specificities to materials while antimicrobial peptides have found roles in preventing biofilm formation on devices and implants. In this progress report, we detail developments in the use of diverse proteins and peptides to modify the surfaces of hard biomaterials in vivo and in vitro. Chemical approaches to immobilizing active biomolecules are presented, as well as platform technologies for isolation or generation of natural or synthetic molecules suitable for biomaterial functionalization.