Cross-kingdom RNA Weapon Weakens Banana Immunity to Fusarium Wilt
image: A proposed model illustrating the virulence mechanism of Foc-milR87. MaPTI6L, an AP2 family transcription factor of banana, can activate the expression of a subset of defense-related genes in response to pathogen infection. MaPTI6L can bind to the GCC-box in the promoter region of MaEDS1 and activate its expression. However, during Fusarium infection, Foc-milR87 enters banana cells and specifically binds to the 3'UTR region of MaPTI6L mRNA to promote the degradation of MaPTI6L mRNA, ultimately suppressing the expression of MaEDS1. Image link: https://academic.oup.com/view-large/figure/507918051/uhae361f8.tif?login=false
Credit: Horticulture Research
Bananas rank among the world’s most valuable staple crops, yet their production faces severe losses from Fusarium wilt caused by Fusarium oxysporum f. sp. cubense (Foc) tropical race 4 (TR4). Current management options are limited, and resistant Cavendish varieties remain elusive. Growing evidence shows that fungal pathogens can deliver small RNAs into host cells to suppress plant immunity through cross-kingdom RNA interference. However, the molecular mechanisms by which TR4 employs such RNA effectors against banana defenses remain unclear. Due to these challenges, uncovering how fungal small RNAs modulate banana immune responses is essential to develop durable resistance.
A research team from the College of Plant Protection at South China Agricultural University has revealed the molecular warfare between banana and the Fusarium wilt pathogen. The study, published (DOI: 10.1093/hr/uhae361) in Horticulture Research on April 1, 2025, demonstrates that the fungal small RNA Foc-milR87 directly targets the banana gene MaPTI6L, suppressing immune signaling and enhancing pathogen virulence. Through cross-species expression analyses and functional assays, the researchers decoded how this microRNA-like molecule impairs plant defense, offering a new target for genetic improvement of banana resistance.
The team discovered that Foc-milR87, produced by F. oxysporum f. sp. cubense, is secreted during the early infection stage and translocated into banana root cells. Once inside, it binds to the 3′ untranslated region (3′UTR) of MaPTI6L mRNA, suppressing its translation. Normally, MaPTI6L—an AP2/ERF family transcription factor—activates the salicylic acid (SA) defense pathway by promoting expression of MaEDS1, a central immune regulator. Overexpressing MaPTI6L in tobacco and Arabidopsis plants triggered reactive oxygen species production, callose deposition, and elevated defense-related gene expression, all of which were attenuated when Foc-milR87 was co-expressed. The researchers further showed that MaPTI6L’s nuclear localization is essential for activating immunity. Sequence comparisons across 19 banana cultivars revealed that resistant varieties harbor single-nucleotide polymorphisms within the Foc-milR87 binding site, which reduces silencing efficiency. Plants carrying this SNP maintained higher MaPTI6L expression and smaller lesion areas after fungal attack. These findings elucidate a cross-kingdom RNA interference mechanism where Foc-milR87 acts as a virulence effector to disarm host immunity.
“Foc-milR87 represents a sophisticated RNA weapon evolved by Fusarium to breach the host’s immune barrier,” said Professor Minhui Li, corresponding author of the study. “Our work provides direct evidence that a fungal microRNA-like RNA can target a specific banana gene to weaken its defense responses. The discovery of resistance-associated SNPs in MaPTI6L offers a natural blueprint for developing Fusarium-resistant bananas without altering essential physiological traits.”
This research uncovers a new molecular strategy employed by the Fusarium pathogen and highlights the potential of small RNA-based manipulation in crop protection. Targeting the 3′UTR of MaPTI6L offers a precise entry point for genome editing or marker-assisted breeding to produce TR4-resistant banana cultivars. Since single-nucleotide substitutions in resistant varieties naturally prevent Foc-milR87 binding, introducing similar mutations could fortify Cavendish bananas against Fusarium wilt. Beyond bananas, this work underscores the importance of understanding cross-kingdom RNA interactions, paving the way for novel RNA-guided resistance breeding in other crops.
###
References
DOI
Original Source URL
https://doi.org/10.1093/hr/uhae361
Funding information
This work was financially supported by the National Natural Science Foundation of China (31871911), the Natural Science Foundation of Guangdong Province (2023A1515012965), and the earmarked fund for China Agricultural Research System (CARS-31).
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2024. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.