Biology subjects

Loganathan, A.

Publications and source records attributed to Loganathan, A..

3 recordsLinked to original sources

bioRxiv2025

Rice NH2 Functions as a Positive Regulator of Salicylic Acid Mediated Defense Responses Against Sheath Blight and Bacterial Blight

The rice genome encodes five non-expressors of pathogenesis-related (NPR) homologs, with OsNPR1/NH1 and OsNPR3/NH3 emerging as pivotal players in salicylic acid (SA)-mediated defense responses. Investigating the functional implications of the remaining NPR/NH genes is critical for the development of disease-resistant rice cultivars. This study explores the role of OsNH2 in rice defense against sheath blight (ShB) using CRISPR/Cas9-edited mutants of the susceptible cultivar ASD16 and the moderately resistant CO51. OsNH2 knockout mutants showed increased susceptibility to ShB, as evidenced by dense mycelial growth, wider hyphae, and elevated superoxide radical content. Two in-frame deletion mutants lacking 15-17 amino acids in the BTB/POZ domain also showed higher susceptibility, highlighting the importance of an intact OsNH2 protein for resistance. qRT-PCR analysis revealed significant downregulation of OsNH1, OsNH3, key transcription factors (WRKY4, WRKY45, WRKY80, TGA2 and TGA3), pathogenesis-related (PR) genes (PR1, PR3 and PR5), and SA biosynthesis genes (PAL and ICS1) in the mutants. Additionally, OsNH2 mutants in both cultivars exhibited reduced endogenous SA levels upon Rhizoctonia solani infection. Exogenous SA treatment partially restored resistance and upregulated OsNH1/3 expression in mutants, though not to wild-type levels. These results suggest that OsNH2 is essential for maintaining SA-mediated defense signaling and optimal expression of NPR1 homologs. Moreover, OsNH2 mutants also showed increased susceptibility to bacterial leaf blight (BLB). Collectively, this research highlights the critical role of OsNH2 in coordinating with OsNH1 and OsNH3 in SA-mediated defense against ShB and BLB in rice. HighlightsCRISPR/Cas9-edited OsNH2 knockout mutants, along with in-frame deletion mutants lacking 15-17 amino acids in the BTB/POZ domain, exhibited increased susceptibility to sheath blight disease in rice. OsNH2 disruption led to reduced endogenous salicylic acid (SA) levels and significant downregulation of OsNH1, OsNH3, key WRKY and TGA transcription factors, and pathogenesis-related (PR) genes. Exogenous SA treatment partially restored resistance and upregulated OsNH1/3 expression in mutants, though not to wild-type levels--highlighting OsNH2s essential role in sustaining SA-mediated defense signaling. OsNH2 mutants also showed increased susceptibility to bacterial leaf blight (BLB), emphasizing its coordination with OsNH1 and OsNH3 in defense against multiple rice pathogens. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=128 SRC="FIGDIR/small/688593v1_ufig1.gif" ALT="Figure 1000"> View larger version (51K): org.highwire.dtl.DTLVardef@f0c18forg.highwire.dtl.DTLVardef@33b59eorg.highwire.dtl.DTLVardef@d8bf27org.highwire.dtl.DTLVardef@1edc5fc_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Evaluation of Phage and Antibiotic Combinations for Staphylococcus aureus Biofilm Eradication: Insights from the Wax Worm Model

BackgroundGalleria mellonella, an advantageous model organism, to investigate the therapeutic potential of bacteriophages. Employing the Galleria mellonella (waxworm) model, this study involved infecting the larvae with pathogenic Staphylococcus aureus, followed by combination treatment with staph phages; vB_Sau_Saa90 and vB_Sau_Saa165 at the concentrations of 107 and 109 PFU/mL and oxacillin, at 100 mg/kg. The treatment modalities were executed in three distinct orders: pre-phage treatment, simultaneous treatment, and post-phage treatment. Each treatment was administered at 90 min intervals. The health state index of the waxworms was monitored throughout the study. ResultsAmong the three treatment orders, both pre-phage treatment and post-antibiotic treatment exhibited the significant outcomes. The survival percentages ranged from 40% to 50%, 30% to 50%, and 50% to 70% across strong, moderate, and weak biofilm conditions. Notably, the phages vB_Sau_Saa90 and vB_Sau_Saa165 displayed remarkable effectiveness in combination with antibiotics. This successful synergy showcased the potential of combinatorial treatment in effectively addressing biofilm-related infections. ConclusionsThis study holds considerable significance as it underscores the suitability of G. mellonella as a model organism for exploring bacteriophage-based therapeutic approaches. The studys findings shed light on the efficacy of combining bacteriophages and antibiotics to target S. aureus biofilm cells. The observed results in the waxworm model highlight a promising avenue for managing biofilm infections. However, the need for further validation through larger animal models is emphasized, as this could potentially pave the way for novel treatment strategies with broader clinical implications.

microbiology↗

bioRxiv2022

A multiwell-plate Caenorhabditis elegans assay for assessing the therapeutic potential of Bacteriophages against Clinical Pathogens

In order to establish phage therapy as a standard clinical treatment for bacterial infections, testing of every phage to ensure the suitability and safety of the biological compound is required. While some issues have been addressed over recent years, standard and easy-to-use animal models to test phages are still rare. Testing of phages in highly suitable mammalian models such as mice is subjected to strict ethical regulations, while insect larvae such as the Galleria mellonella model suffers from batch-to-batch variations and requires manual operator skills to inject bacteria, resulting in unreliable experimental outcomes. A much simpler model is the nematode Caenorhabditis elegans which feeds on bacteria, a fast growing and easy to handle organism which can be used in high-throughput screening. In this study, two clinical bacterial strains of Escherichia coli, one Klebsiella pneumoniae and one Enterobacter cloacae strain were tested on the model system together with lytic bacteriophages that we isolated previously. We developed a liquid-based assay, in which the efficiency of phage treatment was evaluated using a scoring system based on microscopy and counting of the nematodes, allowing increasing statistical significance compared to other assays such as larvae or mice. Our work demonstrates the potential to use Caenorhabditis elegans to test the virulence of strains of Klebsiella pneumoniae, Enterobacter cloacae and EHEC/ EPEC as well as the efficacy of bacteriophages to treat or prevent infections, allowing a more reliable evaluation for the clinical therapeutic potential of lytic phages. ImportanceValidating the efficacy and safety of phages prior to clinical application is crucial to see phage therapy in practice. Current animal models include mice and insect larvae, which pose ethical or technical challenges. This study examined the use of the nematode model organism, C. elegans as a quick, reliable and simple alternative for testing phages. The data shows that all the four tested bacteriophages can eliminate bacterial pathogens and protect the nematode from infections. Survival rates of the nematodes increased from <20% in the infection group to >90% in the phage treatment group. Even the nematodes with poly-microbial infections recovered during phage cocktail treatment. The use of C. elegans as a simple whole-animal infection model is a rapid and robust way to study the efficacy of phages before testing them on more complex model animals such as mice.

microbiology↗