Fusarium wilt of Banana, caused by Fusarium oxysporum f. sp. cubense (Foc), is one of the most devastating diseases affecting global banana production. The pathogen, which inhabits the soil, can survive for decades in the form of chlamydospores even in the absence of host plants, making disease control extremely challenging. In orchards severely affected by Fusarium wilt, traditional Cavendish banana cultivars can no longer be cultivated, highlighting the urgent need to elucidate the pathogenic mechanisms of Foc and to advance breeding programs for resistant banana cultivars.
MicroRNA-like RNAs (milRNAs) are typical small noncoding RNAs produced by fungi that play crucial roles in the interactions between pathogenic fungi and host plants. These milRNAs, usually 19-25 nucleotides in length, are transcribed from single-stranded RNA precursors that can form characteristic stem-loop structures. They function by binding to complementary sequence of target messenger RNAs, thereby repressing target gene expression. However, the specific roles of Foc milRNAs in the pathogenic mechanisms of Foc have been poorly understood until now.
Dr. Minhui Li and her colleagues from South China Agricultural University identified a virulent milRNA, Foc-milR138, which is significantly upregulated during the early stages of Foc infection. They also identified a host receptor-like kinase gene, MaLYK3, as the direct target of this milRNA. Functional investigations revealed that MaLYK3 plays a pivotal role in triggering immune responses in Nicotiana benthamiana by upregulating a suite of resistance genes, bolstering reactive oxygen species accumulation and promoting callose deposition, thereby fortifying disease resistance. This response was markedly subdued when Foc-milR138 was co-expressed with MaLYK3. Expression pattern analysis further verified the specific suppression of MaLYK3 by Foc-milR138 during the early root infection by Foc.
These findings shed light on the roles of milRNAs in the interactions between pathogenic fungi and host plants, identifying potential targets that can be utilized for the development of disease-resistant banana cultivars.
Jiahui He, Jiaqi Zhong, Longqi Jin, Yike Long, Junjian Situ, Chengcheng He, Guanghui Kong, Zide Jiang, and Minhui Li published this work in Molecular Plant Pathology Journal:
TITLE IMAGE: Fusarium oxysporum f. sp. cubense uses an milRNA, Foc-milR138, to suppress banana host immunity by silencing the unconventional receptor-like kinase MaLYK3, which lacks a lysine motif but can still activate plant immune responses.
