Nowadays, it has become urgently necessary to change the traditional methods of synthesis of metallic nanoparticles, and to start using safer and more eco-friendly approaches. In the present work a green synthesis of silver nanoparticles was carried out using mint leaf extract (Mentha piperita) as the reducing and stabilizing agent. Silver nanoparticles were synthesized using a 1 mM silver nitrate solution and varying the volume of the extract (150, 250, 350 μL), at a temperature of 30 °C for 24 h. The formation of silver nanoparticles was monitored by a UV-Visible spectrophotometer which showed absorption peaks ranging from 438–470 nm. Atomic Force Microscopy and Transmission Electron Microscopy analysis showed that the silver nanoparticles presented different morphologies. For the treatment with 150 μl of extract, the silver nanoparticles were mostly spherical and for the other two treatments we observed spherical, triangular, hexagonal and irregular morphologies of the nanoparticles. Dynamic Light Scattering analysis determined a mean size of 50 nm for all of the treatments, with zeta potential values ranging from –20 to –23 mV. The results showed that the synthesized silver nanoparticles had antibacterial activity against pathogenic bacteria such as Escherichia coli and Staphylococcus aureus. The minimum inhibitory concentration required for S. aureus was 11.1, 26.3 and 51.5 μg · ml^–1, for the treatments of 150, 250 and 350 μl of extract, respectively. All of these values were higher than for E. coli, which presented a Minimum Inhibitory Concentration of 2.49 μg · ml^–1. This work offers a quick, simple and non-toxic method for the synthesis of silver nanoparticles.

N⁶-methyladenosine (m⁶A) modification is a dynamically regulated RNA modification that impacts many cellular processes and pathways. This epitranscriptomic methylation relies on the participation of RNA methyltransferases (referred to as “writers”) and demethylases (referred to as “erasers”), respectively. We previously demonstrated that the Arabidopsis thaliana proteinatALKBH9B showed m⁶A-demethylase activity and interacted with the coat protein (CP) of alfalfa mosaic virus (AMV), causing a profound impact on the viral infection cycle. To dissect the functional activity ofatALKBH9B in AMV infection, we performed a protein-mapping analysis to identify the putative domains required for regulating this process. In this context, the mutational analysis of the protein revealed that the residues between 427 and 467 positions are critical forin vitrobinding to the AMV RNA. TheatALKBH9B amino acid sequence showed intrinsically disordered regions (IDRs) located at the N-terminal part delimiting the internal AlkB-like domain and at the C-terminal part. We identified an RNA binding domain containing an RGxxxRGG motif that overlaps with the C-terminal IDR. Moreover, bimolecular fluorescent experiments allowed us to determine that residues located between 387 and 427 are critical for the interaction with the AMV CP, which should be critical for modulating the viral infection process. Finally, we observed thatatALKBH9B deletions of either N-terminal 20 residues or the C-terminal’s last 40 amino acids impede their accumulation in siRNA bodies. The involvement of the regions responsible for RNA and viral CP binding and those required for its localization in stress granules in the viral cycle is discussed.

We have previously reported the presence of m⁶A in the AMV (Alfamovirus, Bromoviridae) genome. Interestingly, two of these putative m⁶A-sites are in hairpin (hp) structures in the 3’UTR of the viral RNA3. One site (₂₀₁₂AAACU₂₀₁₆) is in the loop of hpB, within the coat protein binding site 1 (CPB1), while the other (₁₉₀₀UGACC₁₉₀₄) is in the lower stem of hpE, a loop previously associated with AMV negative-strand RNA synthesis. In this work, we have performed in vivo experiments to assess the role of these two regions, containing the putative m⁶A-sites in the AMV cycle, by introducing compensatory point mutations to interfere with or abolish the m⁶A-tag of these sites. Our results suggest that the loop of hpB could be involved in viral replication/accumulation. Meanwhile, in the ₁₉₀₀UGACC₁₉₀₄ motif of the hpE, the maintenance of the adenosine residue and the lower stem hpE structure are necessary for in vivo plus-strand accumulation. These results extend our understanding of the requirements for hpE in the AMV infection cycle, indicating that both the residue identity and the base-pairing capacity in this structure are essential for viral accumulation.

Blackberries are fruits produced worldwide, with 25 % of their production centered in Mexico, Central and South America. Tropical highland blackberry is a fruit that can potentially enhance human health, due to their high content in phenolic compounds, which include anthocyanins, phenolic acids, tannins (gallotannins and elagitannins) and flavonoids. Therefore, the overall aim of this study is the development of a callus induction protocol, the establishment of blackberry cell suspensions (Rubus adenotrichos Schltdl.) and their cell analysis through optical microscopy and TEM, for the potential production of phenolic compounds. In order to produce callogenesis, segments of blackberry leaves were disinfected and placed in different concentrations of 2,4-D and the control media (0; 0.5; 1.0; 1.5; 2.0; 2.5 and 3.0 mg/l of 2,4-D); obtaining the higher size of calli in the medium with 1.5 mg/l of 2,4-D. After this determination, and for this specific treatment, a growth curve was performed through the use of fresh and dry weight parameters, in order to identify each of the growth stages. Furthermore, the calli obtained from the 1.5 mg/l of 2,4-D treatment were placed in two different culture media (MS and MS supplemented with 1.5 mg/l of 2,4-D) in order to establish the cell suspensions and the growth curve. To the best treatment, the total polyphenols were also quantified. It was determined that the MS medium is ideal for the growth and disintegration of the cell suspensions, obtaining 0.0256 mg of gallic acid/g of fresh sample. Finally, a cell callus and cell suspension analysis was performed through OM and TEM, evidencing a higher hystological differentiation in the calli, as well as the observation of antioxidant storage in the plastids.