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Abstract Background Polygalacturonase inhibiting proteins (PGIPs) play a pivotal role in plant defense against plant pathogens by inhibiting polygalacturonase (PG), an enzyme produced by pathogens to degrade plant cell wall pectin. PGIPs, also known as leucine-rich repeat pathogenesis-related (PR) proteins, activate the host’s defense response upon interaction with PG, thereby reinforcing the host defense against plant pathogens attacks. In Egyptian or extra-long staple cotton (Gossypium barbadense), the interaction between PGIP and PG is one of the crucial steps in the defense mechanism against major pathogens such as Xanthomonas citri pv. malvacearum and Alternaria macrospora, which are responsible for bacterial leaf blight and leaf spot diseases, respectively. Results To unravel the molecular mechanisms underlying these PR proteins, we conducted a comprehensive study involving molecular modeling, protein-protein docking, site-specific double mutation (E169G and F242K), and molecular dynamics simulations. Both wild-type and mutated cotton PGIPs were examined in the interaction with the PG enzyme of a bacterial and fungal pathogen. Our findings revealed that changes in conformations of double-mutated residues in the active site of PGIP lead to the inhibition of PG binding. The molecular dynamics simulation studies provide insights into the dynamic behaviour and stability of the PGIP-PG complexes, shedding light on the intricate details of the inhibitory and exhibitory mechanism against the major fungal and bacterial pathogens of G. barbadense, respectively. Conclusions The findings of this study not only enhance our understanding of the molecular interactions between PGs of Xanthomonas citri pv. malvacearum and Alternaria macrospora and PGIP of G. barbadense but also present a potential strategy for developing the disease-resistant cotton varieties. By variations in the binding affinities of PGs through specific mutations in PGIP, this research offers promising avenues for the development of enhanced resistance to cotton plants against bacterial leaf blight and leaf spot diseases.

The cell wall of the Glycine max altered by the polygalacturonases (PGs) secreted by the fungus Sclerotinia sclerotiorum, causes disease and quality losses. In soybeans, a resistance protein called polygalacturonases-inhibiting proteins (PGIPs) binds to the PG to block fungal infection. The active site residues of PGIP3, VAL170 and GLN242 are mutated naturally by various amino acids in different types of PGIPs. Therefore, the mutation of VAL170 to GLY is ineffective but the GLN242 amino acid mutation by LYS significantly alters the structure and is crucial for interacting with the PG protein. Docking and Molecular Dynamics simulation provide a comprehensive evaluation of the interactions between gmPGIP and ssPG. By elucidating the structural basis of the interaction between gmPGIP and ssPG, this investigation lays a foundation for the development of targeted strategies in-order to enhance soybean resistance against Sclerotinia sclerotiorum. By leveraging this knowledge, researchers can potentially engineer soybean varieties with improved resistance to the fungus, thereby reducing disease incidence and improving crop yields.

The recent emergence of novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causing the coronavirus disease (COVID-19) has become a global public health crisis, and a crucial need exists for rapid identification and development of novel therapeutic interventions. In this study, a recurrent neural network (RNN) is trained and optimized to produce novel ligands that could serve as potential inhibitors to the SARS-CoV-2 viral protease: 3 chymotrypsin-like protease (3CLpro). Structure-based virtual screening was performed through molecular docking, ADMET profiling, and predictions of various molecular properties were done to evaluate the toxicity and drug-likeness of the generated novel ligands. The properties of the generated ligands were also compared with current drugs under various phases of clinical trials to assess the efficacy of the novel ligands. Twenty novel ligands were selected that exhibited good drug-likeness properties, with most ligands conforming to Lipinski’s rule of 5, high binding affinity (highest binding affinity: −9.4 kcal/mol), and promising ADMET profile. Additionally, the generated ligands complexed with 3CLpro were found to be stable based on the results of molecular dynamics simulation studies conducted over a 100 ns period. Overall, the findings offer a promising avenue for the rapid identification and development of effective therapeutic interventions to treat COVID-19.

PolyGalacturonase Inhibiting Proteins (PGIPs) are leucine rich repeat pathogenesis-related (PR) cell wall proteins, which interact and inhibit the PolyGalacturonase (PG), an enzyme secreted by the pathogen to degrade pectin. Interaction of PGIP with PG limits the vulnerability of PG by the activation of host defense response against pathogenic attack. Erwinia is gram-negative soft rot bacteria responsible for rhizome rot disease in banana and many other crop plants. The interaction of PG with PGIP is one of the crucial steps for plant-pathogen interaction. To study the molecular mechanism of PR proteins, we employed molecular modelling, protein-protein docking and molecular dynamics simulations of banana PGIP (bPGIP) with Erwinia carotovora PG (ecPG). Further, insilico site-directed mutagenesis was performed in Phaseolus vulgaris PGIP (pvPGIP2) to elucidate the interaction with ecPG. Docking and simulation studies divulge that binding of bPGIP and PvPGIP2 with active site residues of EcPG induces structural changes and thereby inhibit the enzyme. This study provides a unique insight into PG-PGIP interaction, which may help in the development of bacterial soft-rot resistant banana cultivars.