Altered TMPRSS2 usage by SARS-CoV-2 Omicron impacts infectivity and fusogenicity

The SARS-CoV-2 Omicron BA.1 variant emerged in 20211 and has multiple mutations in its spike protein2. Here we show that the spike protein of Omicron has a higher affinity for ACE2 compared with Delta, and a marked change in its antigenicity increases Omicron’s evasion of therapeutic monoclonal and vaccine-elicited polyclonal neutralizing antibodies after two doses. mRNA vaccination as a third vaccine dose rescues and broadens neutralization. Importantly, the antiviral drugs remdesivir and molnupiravir retain efficacy against Omicron BA.1. Replication was similar for Omicron and Delta virus isolates in human nasal epithelial cultures. However, in lung cells and gut cells, Omicron demonstrated lower replication. Omicron spike protein was less efficiently cleaved compared with Delta. The differences in replication were mapped to the entry efficiency of the virus on the basis of spike-pseudotyped virus assays. The defect in entry of Omicron pseudotyped virus to specific cell types effectively correlated with higher cellular RNA expression of TMPRSS2, and deletion of TMPRSS2 affected Delta entry to a greater extent than Omicron. Furthermore, drug inhibitors targeting specific entry pathways3 demonstrated that the Omicron spike inefficiently uses the cellular protease TMPRSS2, which promotes cell entry through plasma membrane fusion, with greater dependency on cell entry through the endocytic pathway. Consistent with suboptimal S1/S2 cleavage and inability to use TMPRSS2, syncytium formation by the Omicron spike was substantially impaired compared with the Delta spike. The less efficient spike cleavage of Omicron at S1/S2 is associated with a shift in cellular tropism away from TMPRSS2-expressing cells, with implications for altered pathogenesis

In vitro cloning of Bambusa pallida Munro through axillary shoot proliferation and evaluation of genetic fidelity by random amplified polymorphic DNA markers

Multiple shoots emerged from the nodal shoot segments of the field-grown candidate plus clump explants of <em>Bambusa pallida </em>Munro when cultured on Murashige and Skoog (MS) liquid medium with additives (ascorbic acid 50 mg/L + citric acid 25 mg/L + cysteine 25 mg/L) and combined use of α-naphthalene acetic acid (NAA) 1.34 μM + thiodiozuron 1.125 μM in a 2-week period. Further shoot multiplication was achieved in MS liquid medium with additives + NAA 1.34 μM + 6-benzylaminopurine 4.4 μM at 25±2°C and 33.78 μmol photons m-2 s-1 light illumination for a 12-h photoperiod. These shoots were rooted within four weeks in MS/2 basal salt medium with additives + 2% sucrose +1% glucose, and 0.6% agar by pulse treatment of shoots with indole 3 butyric acid 0.5 mg/mL for 30 min prior to inoculation. Rooted plants were successfully hardened in the mist chamber. Survival rate during hardening was more than 95%. Micropropagated plants achieved a height of 25-30 cm with 3-4 tillers (shoots) with miniature rhizome in a 4-month period. Genetic stability was observed in the micropropagated plants