Salinity is one of the major anthropogenic as well as environmental stresses that reduce plant growth. Results show that even after being adapted up to 6% sodium chloride (NaCl) concentration, all selected isolates were able to solubilize phosphate, and produce phytohormones, siderophores and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase enzyme. NT1 was found to exhibit the highest phosphate solubilization zones (25 mm), siderophore production (1000 mg ml (1 ) as well as ACC deaminase production (50 mMmg (1 h (1 ) potential under laboratory conditions. On the other hand, pot studies conducted on tomato plants under 2% NaCl stress proved that C4 and T15 were the best growth promoters. C4 showed 50% enhancement in root and shoot length as compared to NaCl added untreated plants as well as in absence of NaCl. C4 also enhanced salinity tolerance in plants with the lowest uptake of NaCl thereby reducing the salt stress on plants. C5 enhanced biomass production in tomato plants with increased uptake of the salts by plants, thereby reducing the salt concentration in the soil. The study thus shows that the selected isolates can be used for the plant growth promotion of plants under salinity stress.

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The health of the plant and soil fertility is dependent on the plant-microbes interaction in the rhizosphere. Microbial life tends to endure various rhizosphere plant-microbe interactions. Phytohormones such as auxins, cytokinins, gibberellic acid, ethylene and abscisic acid are termed as the classical group of hormones. Out of the 70 rhizobacterial strains isolated from the Coleus rhizosphere, three different rhizobacterial strains Pseudomonas stutzeri MTP40, Stenotrophomonas maltophilia MTP42 and Pseudomonas putida MTP50 having plant growth-promoting attributes were isolated and characterized for its phytohormone-producing ability. The phytohormones such as indole 3-acetic acid (IAA), gibberellic acid and cytokinin (kinetin and 6-benzyladenosine) were affirmed in culture supernatant of the above isolates. IAA was detected in all the three isolates, where in highest production was found in S. maltophilia MTP42 (240 µg/mL) followed by P. stutzeri MTP40 (250 µg/mL) and P. putida MTP50 (233 µg/mL). Gibberellic acid production was found maximum in MTP40 (34 µg/mL), followed by MTP42 (31 µg/mL) and MTP50 (27 µg/mL). The cytokinin production from the isolates, namely, MTP40, MTP42 and MTP50 were 13, 11 and 7.5 µg/ mL, respectively. The isolates showing the production of plant growth enhancing phytohormones can be commercialized as potent bioformulations.

The novel SARS-CoV-2 is the etiological agent causing the Coronavirus disease 2019 (COVID-19), which continues to become an inevitable pandemic outbreak. Over a short span of time, the structures of therapeutic target proteins for SARS-CoV-2 were identified based on the homology modelled structure of similar SARS-CoV transmission of 2003. Since the onset of the disease, the research community has been looking for a potential drug lead. Out of all the known resolved structures related to SARS-CoV, Main protease (M pro ) is considered an attractive anti-viral drug target on the grounds of its role in viral replication and probable non-interactive competency to bind to any viral host protein. To the best of our knowledge, till date only one compound has been identified and tested in-vivo as a potent inhibitor of M pro protein, addressed as N3 (PubChem Compound CID: 6323191) and is known to bind irreversibly to M pro suppressing its activity. Using computational approach, we intend to identify a probable natural fungal metabolite to interact and inhibit M pro . After screening various small molecules for molecular docking and dynamics simulation, we propose Pyranonigrin A, a secondary fungal metabolite to possess potent inhibitory potential against the Main protease (M pro ) expressed in SARS-CoV-2 virus.

The non-structural protein (nsp)-3 of SARS-CoV2 coronavirus is sought to be an essential target protein which is also named as papain-like protease (PLpro). This protease cleaves the viral polyprotein, but importantly in human host it also removes ubiquitin-like interferon-stimulated gene 15 protein (ISG15) from interferon responsive factor 3 (IRF3) protein which ultimately downregulates the production of type I interferon leading to weakening of immune response. GRL0617 is the most potent known inhibitor for PLpro that was initially developed for SARS outbreak of 2003. The PLpro of SARS-CoV and CoV2 share 83% sequence identity but interestingly have several identical conserved amino acids that suggests GRL0617 to be an effective inhibitor for PLpro of SARS-CoV2. GRL0617 is a naphthalene-based molecule and interacts with Tyr268 of SARS-CoV2-PLpro (and Tyr269 of SARS-CoV-PLpro). To identify PLpro inhibitors, we prepared a library of secondary metabolites from fungi with aromatic nature and docked them with PLpro of SARS-CoV and SARS-CoV2. We found six hits which interacts with Tyr268 of SARS-CoV2-PLpro (and Tyr269 of SARS-CoV-PLpro). More surprisingly the top hit, Fonsecin, has naphthalene moiety in its structure, which recruits Tyr268 of SARS-CoV2-PLpro (and Tyr269 of SARS-CoV-PLpro) and has binding energy at par with control (GRL0617). Molecular dynamics (MD) simulation showed Fonsecin to interact with Tyr268 of SARS-CoV2-PLpro more efficiently than control (GRL0617) and interacting with a greater number of amino acids in the binding cleft of PLpro. Graphic abstract