| Summary: | <i>Fusarium oxysporum</i> is the most important pathogen of potatoes which causes post-harvest destructive losses and deteriorates the market value of potato tubers worldwide. Here, <i>F. oxysporum</i> was used as a host pathogen model system and it was revealed that autophagy plays a vital role as a regulator in the morphology, cellular growth, development, as well as the pathogenicity of <i>F. oxysporum</i>. Previous studies based upon identification of the gene responsible for encoding the autophagy pathway components from <i>F. oxysporum</i> have shown putative orthologs of 16 core autophagy related-<i>ATG</i> genes of yeast in the genome database which were autophagy-related and comprised of ubiquitin-like protein <i>atg3</i>. This study elucidates the molecular mechanism of the autophagy-related gene <i>Foatg3</i> in <i>F. oxysporum</i>. A deletion (∆) mutants of <i>F. oxysporum</i> (<i>Foatg3</i>∆) was generated to evaluate nuclear dynamics. As compared to wild type and <i>Foatg3</i> overexpression (OE) strains, <i>Foatg3∆</i> strains failed to show positive MDC (monodansylcadaverine) staining which revealed that <i>Foatg3</i> is compulsory for autophagy in <i>F. oxysporum</i>. A significant reduction in conidiation and hyphal growth was shown by the <i>Foatg3∆</i> strains resulting in loss of virulence on potato tubers. The hyphae of <i>Foatg3</i>∆ mutants contained two or more nuclei within one hyphal compartment while wild type hyphae were composed of uninucleate hyphal compartments. Our findings reveal that the vital significance of <i>Foatg3</i> as a key target in controlling the dry rot disease in root crops and potato tubers at the postharvest stage has immense potential of disease control and yield enhancement.
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