Musa acuminata LRR-RLK genes are involved in the response of banana to Fusarium oxysporum f. sp. cubense tropical race 4

As a large and essential gene family conserved across the plant kingdom, LRR-RLKs play critical roles in plant growth, development, and immunity against pathogens. However, little is known about how banana LRR-RLK genes regulate plant resistance to Fusarium oxysporum f. sp. cubense Tropical Race 4 ( Foc TR4), the causal agent of Fusarium wilt (Panama disease) of banana. Genome-wide screening of banana genomic data uncovered 316 LRR-RLK genes that were classified into 22 subgroups. Phylogenetic and conserved motif analyses showed that LRR-RLK paralogs within the same evolutionary clade share highly conserved structural features. Transcriptome expression profiling revealed diverse expression patterns among these genes in resistant and susceptible banana cultivars under Foc TR4 infection. Upon Foc TR4 infection, MaLRR-RLK177 was significantly and persistently down-regulated at all sampled time points in the susceptible cultivar Z1. In the RNA-Seq data for the resistant cultivar Z8, this gene showed only a minor, statistically non-significant increase at 2 days post-inoculation (dpi), followed by significant down-regulation at 4 dpi. The substantial expression difference between the two genotypes at 2 dpi mainly stemmed from drastic transcriptional suppression of this gene in Z1. Transient RNAi-mediated silencing of MaLRR-RLK177 increased the susceptibility of banana leaves to Foc TR4, indicating that this gene participates in leaf-level defense responses. This study characterizes the transcriptional landscape of the banana LRR-RLK family and identifies MaLRR-RLK177 as a promising candidate gene for banana disease-resistance breeding. Not applicable.