Nicotiana benthamiana is a suitable transient system for high-level expression of an active inhibitor of cotton boll weevil α-amylase

Combined sensory, volatilome and transcriptome analyses identify a limonene terpene synthase as a major contributor to the characteristic aroma of a Coffea arabica L. specialty coffee

BACKGROUND

The fruity aromatic bouquet of coffee has attracted recent interest to differentiate high value market produce as specialty coffee. Although the volatile compounds present in green and roasted coffee beans have been extensively described, no study has yet linked varietal molecular differences to the greater abundance of specific substances and support the aroma specificity of specialty coffees.

RESULTS

This study compared four Arabica genotypes including one, Geisha Especial, suggested to generate specialty coffee. Formal sensory evaluations of coffee beverages stressed the importance of coffee genotype in aroma perception and that Geisha Especial-made coffee stood out by having fine fruity, and floral, aromas and a more balanced acidity. Comparative SPME-GC-MS analyses of green and roasted bean volatile compounds indicated that those of Geisha Especial differed by having greater amounts of limonene and 3-methylbutanoic acid in agreement with the coffee cup aroma perception. A search for gene ontology differences of ripening beans transcriptomes of the four varieties revealed that they differed by metabolic processes linked to terpene biosynthesis due to the greater gene expression of prenyl-pyrophosphate biosynthetic genes and terpene synthases. Only one terpene synthase (CaTPS10-like) had an expression pattern that paralleled limonene loss during the final stage of berry ripening and limonene content in the studied four varieties beans. Its functional expression in tobacco leaves confirmed its functioning as a limonene synthase.

CONCLUSIONS

Taken together, these data indicate that coffee variety genotypic specificities may influence ripe berry chemotype and final coffee aroma unicity. For the specialty coffee variety Geisha Especial, greater expression of terpene biosynthetic genes including CaTPS10-like, a limonene synthase, resulted in the greater abundance of limonene in green beans, roasted beans and a unique citrus note of the coffee drink.

Insect α-Amylases and Their Application in Pest Management

Amylase is an indispensable hydrolase in insect growth and development. Its varied enzymatic parameters cause insects to have strong stress resistance. Amylase gene replication is a very common phenomenon in insects, and different copies of amylase genes enable changes in its location and function. In addition, the classification, structure, and interaction between insect amylase inhibitors and amylases have also invoked the attention of researchers. Some plant-derived amylase inhibitors have inhibitory activities against insect amylases and even mammalian amylases. In recent years, an increasing number of studies have clarified the effects of pesticides on the amylase activity of target and non-target pests, which provides a theoretical basis for exploring safe and efficient pesticides, while the exact lethal mechanisms and safety in field applications remain unclear. Here, we summarize the most recent advances in insect amylase studies, including its sequence and characteristics and the regulation of amylase inhibitors (α-AIs). Importantly, the application of amylases as the nanocide trigger, RNAi, or other kinds of pesticide targets will be discussed. A comprehensive foundation will be provided for applying insect amylases to the development of new-generation insect management tools and improving the specificity, stability, and safety of pesticides.

Co-transient expression of PSA-Fc and PAP-Fc fusion protein in plant as prostate cancer vaccine candidates and immune responses in mice

KEY MESSAGE

PAP-FcK and PSA-FcK prostate cancer antigenic proteins transiently co-expressed in plant induce their specific humoral immune responses in mice. Prostate-specific antigen (PSA) and prostatic acid phosphatase (PAP) have been considered as immunotherapeutic antigens for prostate cancer. The use of a single antigenic agent is unlikely to be effective in eliciting immunotherapeutic responses due to the heterogeneous and multifocal nature of prostate cancer. Thus, multiple antigens have been combined to enhance their anti-cancer effects. In the current study, PSA and PAP were fused to the crystallizable region (Fc region) of immunoglobulin G1 and tagged with KDEL, the endoplasmic reticulum (ER) retention signal motif, to generate PSA-FcK and PAP-FcK, respectively, and were transiently co-expressed in Nicotiana benthamiana. Western blot analysis confirmed the co-expression of PSA-FcK and PAP-FcK (PSA-FcK + PAP-FcK) with a 1:3 ratios in the co-infiltrated plants. PSA-FcK, PAP-FcK, and PSA-FcK + PAP-FcK proteins were successfully purified from N. benthamiana by protein A affinity chromatography. ELISA showed that anti-PAP and anti-PSA antibodies successfully detected PAP-FcK and PSA-FcK, respectively, and both detected PSA-FcK + PAP-FcK. Surface plasmon resonance (SPR) analysis confirmed the binding affinity of the plant-derived Fc fusion proteins to FcγRI/CD64. Furthermore, we also confirmed that mice injected with PSA-FcK + PAP-FcK produced both PSA- and PAP-specific IgGs, demonstrating their immunogenicity. This study suggested that the transient plant expression system can be applied to produce the dual-antigen Fc fusion protein (PSA-FcK + PAP-FcK) for prostate cancer immunotherapy.

High-level transient production of a protease-resistant mutant form of human basic fibroblast growth factor in Nicotiana benthamiana leaves

The human basic fibroblast growth factor (bFGF) is a protein that plays a pivotal role in cellular processes like cell proliferation and development. As a result, it has become an important component in cell culture systems, with applications in biomedical engineering, cosmetics, and research. Alternative production techniques, such as transient production in plants, are becoming a feasible option as the demand continues to grow. High-level bFGF production was achieved in this study employing an optimized Agrobacterium-mediated transient expression system, which yielded about a 3-fold increase in production over a conventional system. This yield was further doubled at about 185 µg g^-1 FW using a mutant protease-resistant version that degraded/aggregated at a three-fold slower rate in leaf crude extracts. To achieve a pure product, a two-step purification technique was applied. The capacity of the pure protease-resistant bFGF (PRbFGF) to stimulate cell proliferation was tested and was found to be comparable to that of E. coli-produced bFGF in HepG2 and CHO-K1 cells. Overall, this study demonstrates a high-level transient production system of functional PRbFGF in N. benthamiana leaves as well as an efficient tag-less purification technique of leaf crude extracts.

RIN4 homologs from important crop species differentially regulate the Arabidopsis NB-LRR immune receptor, RPS2

KEY MESSAGE

RIN4 homologs from important crop species differ in their ability to prevent ectopic activity of the nucleotide binding-leucine rich repeat resistance protein, RPS2. Pathogens deploy virulence effectors to perturb host processes. Plants utilize intracellular resistance (R) proteins to recognize pathogen effectors either by direct interaction or indirectly via effector-mediated perturbations of host components. RPM1-INTERACTING PROTEIN4 (RIN4) is a plant immune regulator that mediates the indirect activation of multiple, independently evolved R-proteins by multiple, unrelated effector proteins. One of these, RPS2 (RESISTANT TO P. SYRINGAE2), is activated upon cleavage of Arabidopsis (At)RIN4 by the Pseudomonas syringae effector AvrRpt2. To gain insight into the AvrRpt2-RIN4-RPS2 defense-activation module, we compared the function of AtRIN4 with RIN4 homologs present in a diverse range of plant species. We selected seven homologs containing conserved features of AtRIN4, including two NOI (Nitrate induced) domains, each containing a predicted cleavage site for AvrRpt2, and a C-terminal palmitoylation site predicted to mediate membrane tethering of the proteins. Palmitoylation-mediated tethering of AtRIN4 to the plasma membrane and cleavage by AvrRpt2 are required for suppression and activation of RPS2, respectively. While all seven homologs are localized at the plasma membrane, only four suppress RPS2 when transiently expressed in Nicotiana benthamiana. All seven homologs are cleaved by AvrRpt2 and, for those homologs that are able to suppress RPS2, cleavage relieves suppression of RPS2. Further, we demonstrate that the membrane-tethered, C-terminal AvrRpt2-generated cleavage fragment is sufficient for the suppression of RPS2. Lastly, we show that the membrane localization of RPS2 is unaffected by its suppression or activation status.

Optimization of the human colorectal carcinoma antigen GA733-2 production in tobacco plants

The colorectal carcinoma-associated protein GA733-2 is one of the representative candidate protein for the development of plant-derived colorectal cancer vaccine. Despite of its significant importance for colorectal vaccine development, low efficiency of GA733-2 production limits its wide applications. To improve productivity of GA733-2 in plants, we here tested multiple factors that affect expression of recombinant GA733-2 (rGA733-2) and rGA733 fused to fragment crystallizable (Fc) domain (rGA733-Fc) protein. The rGA733-2 and rGA733-Fc proteins were highly expressed when the pBINPLUS vector system was used for transient expression in tobacco plants. In addition, the length of interval between rGA733-2 and left border of T-DNA affected the expression of rGA733 protein. Transient expression analysis using various combinations of Agrobacterium tumefaciens strains (C58C1, LBA4404, and GV3101) and tobacco species (Nicotiana tabacum cv. Xanthi nc and Nicotiana benthamiana) revealed that higher accumulation of rGA733-2 and rGA733-Fc proteins were obtained by combination of A. tumefaciens LBA4404 and Nicotiana benthamiana. Transgenic plants generated by introduction of the rGA733-2 and rGA733-Fc expression cassettes also significantly accumulated corresponding recombinant proteins. Bioactivity and stability of the plant-derived rGA733 and rGA733-Fc were evaluated by further in vitro assay, western blot and N-glycosylation analysis. Collectively, we here suggest the optimal condition for efficient production of functional rGA733-2 protein in tobacco system.