Humans can be infected by SARS-CoV-2 either through inhalation of airborne viral particles or by touching contaminated surfaces. Structural and functional studies have shown that a single RBD of the SARS-CoV-2 homotrimer spike glycoprotein interacts with ACE2, which serves as its receptor 1,2 . Binding of spike (S) protein to ACE2 and subsequent cleavage by the host protease transmembrane serine protease 2 (TMPRSS2) results in cell and virus membrane fusion and cell entry 1 . Blocking of the ACE2 receptor by specific antibodies prevents viral entry 1,3-5 . In vitro binding measurements have shown that SARS-CoV-2 S protein binds ACE2 with an affinity of around 10 nM, which is about tenfold tighter than the binding of the SARS-CoV S protein 2,4,6 . It has been suggested that this is, at least partially, responsible for the higher infectivity of SARS-CoV-2 7 . Recently, three major SARS-CoV2 variants of concern have emerged and mutations in the RBD of the spike proteins of these variants have further strengthened this hypothesis. Deep-mutational scanning of the RBD domain showed that the N501Y mutation in the Alpha variant to enhances binding to ACE2 7 . The Beta variant has three altered residues in the ACE2-binding site (K417N, E484K and N501Y), and has spread extremely rapidly, becoming the dominant lineage in the Eastern Cape and Western Cape Provinces within weeks 8 . The Gamma variant, with independent K417T, E484K and N501Y mutations, similar to the B.1.351 variant is spreading rapidly from the Amazon region 9 . Another S mutation associated with increased SARS-CoV-2 infectivity is S477N, which became dominant in many regions 10 .Efficacious vaccines are now being administered 11 . However, especially when a large fraction of the global population remains unvaccinated, the potential of the continuously mutating virus to become at least partially resistant to vaccines means that drug development must continue. Potential therapeutic targets that block viral entry include molecules that block the spike protein, the TMPRSS2 protease or the ACE2 receptor 12 . Multiple high-affinity neutralizing antibodies have been developed 13 . Soluble forms of the ACE2 protein 14,15 or engineered parts or mimics have also shown efficacy 16,17 . In addition, previously developed TMPRSS2 inhibitors have been repurposed for treatment of COVID-19 1 .The development of molecules to block the ACE2 protein has not received much attention. One potential caveat with this approach is the importance of ACE2 biological activity, both as a carboxypeptidase removing a single C-terminal amino acid from angiotensin II to generate angiotensin-(1-7) and in the regulation of amino acid transport and pancreatic insulin secretion 18,19 . Dalbavancin is a drug that blocks the spike protein-ACE2 interaction, however it does so with low affinity 20 (approximately 130 nM).We hypothesized that the RBD domain of SARS-CoV-2 could be used as a competitive inhibitor of the ACE2 receptor binding site. However, this would probably require an RBD with picomola...

Floral scent, which is determined by a complex mixture of low molecular weight volatile molecules, plays a major role in the plant's life cycle. Phenylpropanoid volatiles are the main determinants of floral scent in petunia (Petunia hybrida). A screen using virus-induced gene silencing for regulators of scent production in petunia flowers yielded a novel R2R3-MYB–like regulatory factor of phenylpropanoid volatile biosynthesis, EMISSION OF BENZENOIDS II (EOBII). This factor was localized to the nucleus and its expression was found to be flower specific and temporally and spatially associated with scent production/emission. Suppression of EOBII expression led to significant reduction in the levels of volatiles accumulating in and emitted by flowers, such as benzaldehyde, phenylethyl alcohol, benzylbenzoate, and isoeugenol. Up/downregulation of EOBII affected transcript levels of several biosynthetic floral scent-related genes encoding enzymes from the phenylpropanoid pathway that are directly involved in the production of these volatiles and enzymes from the shikimate pathway that determine substrate availability. Due to its coordinated wide-ranging effect on the production of floral volatiles, and its lack of effect on anthocyanin production, a central regulatory role is proposed for EOBII in the biosynthesis of phenylpropanoid volatiles.

Zinc finger nucleases (ZFNs) are a powerful tool for genome editing in eukaryotic cells. ZFNs have been used for targeted mutagenesis in model and crop species. In animal and human cells, transient ZFN expression is often achieved by direct gene transfer into the target cells. Stable transformation, however, is the preferred method for gene expression in plant species, and ZFN-expressing transgenic plants have been used for recovery of mutants that are likely to be classified as transgenic due to the use of direct gene-transfer methods into the target cells. Here we present an alternative, nontransgenic approach for ZFN delivery and production of mutant plants using a novel Tobacco rattle virus (TRV)-based expression system for indirect transient delivery of ZFNs into a variety of tissues and cells of intact plants. TRV systemically infected its hosts and virus ZFN-mediated targeted mutagenesis could be clearly observed in newly developed infected tissues as measured by activation of a mutated reporter transgene in tobacco (Nicotiana tabacum) and petunia (Petunia hybrida) plants. The ability of TRV to move to developing buds and regenerating tissues enabled recovery of mutated tobacco and petunia plants. Sequence analysis and transmission of the mutations to the next generation confirmed the stability of the ZFN-induced genetic changes. Because TRV is an RNA virus that can infect a wide range of plant species, it provides a viable alternative to the production of ZFN-mediated mutants while avoiding the use of direct plant-transformation methods.

The ␤-glucosidase from Aspergillus niger (CMI CC 324262) was purified, and an N-terminal sequence and two internal sequences were determined. BglI genomic gene and the cDNA were cloned from a genomic library and by reverse transcriptase-polymerase chain reaction, respectively. The cDNA was successfully expressed in Saccharomyces cerevisiae and Pichia pastoris. Sequence analysis revealed that the gene encodes a 92-kDa enzyme that is a member of glycosidase family 3. 1 H-NMR analysis of the reaction catalyzed by this enzyme confirmed that, in common with other family 3 glycosidases, this enzyme hydrolyzes with net retention of anomeric configuration. Accordingly, the enzyme was inactivated by 2-deoxy-2-fluoro ␤-glucosyl fluoride, with kinetic parameters of k i ‫؍‬ 4. ␤-Glucosidases (EC 3.2.1.21; ␤-D-glucoside glucohydrolase) play a number of different important roles in biology, including the degradation of cellulosic biomass by fungi and bacteria, degradation of glycolipids in mammalian lysosomes, and the cleavage of glucosylated flavonoids in plants. These enzymes are therefore of considerable industrial interest, not only as constituents of cellulose-degrading systems, but also in the food industry (2, 3).Aspergillus species are known as a useful source of ␤-glucosidases (4 -6), and Aspergillus niger is by far the most efficient producer of ␤-glucosidase among the microorganisms investigated (4). Shoseyov et al. (7) have described a ␤-glucosidase from A. niger B1 (CMI CC 324626), which is active at low pH values as well as in the presence of high ethanol concentrations. This enzyme effectively hydrolyzes flavor compound glycosides in certain low pH products, such as wine and passion fruit juice, thereby enhancing their flavor (8 -11) and is particularly attractive for use in the food industry because A. niger is considered nontoxic (3). Other A. niger ␤-glucosidases have also been purified (12-14); however, differences in their properties have been reported, including ranges of molecular masses (116 -137 kDa) and isoelectric points (pI values of 3.8 -4) and pH optima (3.4 -4.5). Indeed, at least two ␤-glucosidases with distinct substrate specificities have been identified in commercial A. niger ␤-glucosidase preparations (15). To clear this confusion and also to allow protein engineering work to be performed it was important to clone, express, and characterize a ␤-glucosidase from this source. Although the cloning and expression of a functional A. niger ␤-glucosidase gene in Saccharomyces cerevisiae has been reported previously (16), the protein was not characterized, and the sequence was not published.Glycosidases have been assigned to families on the basis of sequence similarities, there now being some 77 different such families defined containing over 2000 different enzymes (17) With the exception of the glucosylceramidases (family 30) all simple ␤-glucosidases belong to either family 1 or 3. Family 1 contains enzymes from bacteria, plants, and mammals including also 6-phospho-glucosidases and thioglucosidas...