A Novel Effector, FSE1, Regulates the Pathogenicity of Fusarium oxysporum f. sp. cubense Tropical Race 4 to Banana by Targeting the MYB Transcription Factor MaEFM-Like

Phytopathogenic fungi secretes a range of effectors to manipulate plant defenses. Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4) is a soil-borne pathogen that causes destructive banana wilt disease. Understanding the molecular mechanisms behind Foc TR4 effectors and their regulation of pathogenicity is helpful for developing disease control strategies. In the present study, we identified a novel effector, Fusarium special effector 1 (FSE1), in Foc TR4. We constructed FSE1 knock-out and overexpression mutants and investigated the functions of this effector. In vitro assays revealed that FSE1 was not required for vegetative growth and conidiation of Foc TR4. However, inoculation analysis of banana plantlets demonstrated that knock-out of FSE1 increased the disease index, while overexpression of FSE1 decreased it. Microscope analysis suggested that FSE1 was distributed in the cytoplasm and nuclei of plant cells. Furthermore, we identified an MYB transcription factor, MaEFM-like, as the target of FSE1, and the two proteins physically interacted in the nuclei of plant cells. In addition, Transient expression of MaEFM-like induced cell death in tobacco leaves. Our findings suggest that FSE1 is involved in the pathogenicity of Foc TR4 by targeting MaEFM-like.

Draft Genome of Fusarium oxysporum f. sp. cubense Strain Tropical Race-4 Infecting Cavendish (AAA) Group of Banana in India

Fusarium wilt, caused by the fungus Fusarium oxysporum f. sp. cubense, is the most serious pandemic disease of banana. In this study, we report the draft genome of F. oxysporum f. sp. cubense vegetative compatibility group (VCG) 01213/16 of strain tropical race 4 (TR4) that infects the Cavendish (AAA) group of banana collected from the subtropical region in India. The genome assembly of SFoc TR4 comprises 47,384,463 bp with 4,034 contigs and 15,508 protein-coding regions. Based on VCG analysis, the fungal isolate belongs to F. oxysporum f. sp. cubense TR4 but the genome sequence of SFoc TR4 shows differences in secreted-in-xylem (SIX) protein gene clusters (specifically, SIX8) in comparison with the reference genome of F. oxysporum f. sp. lycopersici and F. oxysporum f. sp. cubense TR4.

Anti-Foc RT4 Activity of a Newly Isolated Streptomyces sp. 5-10 From a Medicinal Plant (Curculigo capitulata)

Fusarium wilt of banana caused by Fusarium oxysporum f. sp. cubense (Foc) is a disastrous soil-borne fungal disease. Foc tropical race 4 (Foc TR4) can infect almost all banana cultivars. Until now, there is a shortage of safety and effective control methods and commercial banana cultivars with a resistance against Foc TR4. Biocontrol using environmentally friendly microbes is a promising strategy for the management of Foc TR4. Here, a strain 5-10, newly isolated from a medicinal plant (Curculigo capitulata), exhibited a high antifungal activity against Foc TR4. Combing the morphological characteristics and molecular identification, strain 5-10 was classified as a Streptomyces genus. The sequenced genome revealed that more than 39 gene clusters were involved in the biosynthesis of secondary metabolites. Some multidrug resistance gene clusters were also identified such as mdtD, vatB, and vgaE. To improve the anti-Foc TR4 activity of the strain 5-10 extracts, an optimization method of fermentation broth was established. Antifungal activity increased by 72.13% under the fermentation system containing 2.86 g/L of NaCl and 11.57% of inoculation amount. After being treated with the strain 5-10 extracts, the Foc TR4 hyphae shrinked, deformed, and ruptured. The membrane integrity and cell ultrastructure incurred irreversible damage. Streptomyces sp. 5-10 extracts play a fungicidal role in Foc TR4. Hence, Streptomyces sp. 5-10 will be a potential biocontrol agent to manage fungal diseases by exploring the microbial fertilizer.