Genome-wide analysis of wall-associated kinase (WAK/WAKL) family in banana reveals MaWAKL33 as a candidate gene associated with resistance to Fusarium oxysporum f. sp. cubense tropical race 4

Background Wall-associated kinase (WAK) and WAK-like proteins (WAKL) are receptor-like kinases that play pivotal roles in plant immunity. Fusarium wilt of banana, caused by Fusarium oxysporum f. sp. cubense tropical race 4 ( Foc TR4), poses a major threat to global banana production. However, the functions of WAK/WAKL genes in banana resistance to Foc TR4 remain unknown. Results A total of 13 MaWAK and 67 MaWAKL genes were identified in the Musa acuminata ‘DH-Pahang’ genome and were unevenly distributed across 11 chromosomes. Genome-wide analyses revealed diversity in their physicochemical properties, conserved domain architectures, gene structures, and evolutionary relationships. Promoter analysis identified numerous cis -acting regulatory elements associated with phytohormone signaling and stress responses. Transcriptome profiling and RT-qPCR revealed distinct expression patterns of MaWAK/MaWAKL genes in the Foc TR4-susceptible cultivar ‘Tianbao’ and the highly resistant cultivar ‘GCTCV119’. Among these genes, MaWAKL33 , located within the major quantitative trait locus (QTL) for Fusarium oxysporum f. sp. cubense physiological race 4 resistance on chromosome 3, which confers resistance to both Tropical Race 4 (TR4) and Subtropical Race 4 (STR4), showed progressively increasing expression in roots of the resistant cultivar throughout infection, whereas its expression remained largely unchanged in the susceptible cultivar. The MaWAKL33 promoter contains multiple methyl jasmonate (MeJA)-responsive elements. Consistent with this, MeJA-responsive marker genes showed higher basal expression in the resistant cultivar before inoculation, whereas salicylic acid (SA)-responsive marker genes were strongly induced at 12 h post-inoculation and displayed significantly different expression patterns between the two cultivars. Conclusions These findings provide the first comprehensive characterization of the banana WAK/WAKL gene family and identify MaWAKL33 as a candidate gene associated with resistance to Foc TR4. The expression pattern and promoter architecture of MaWAKL33 , together with the differential expression of hormone-responsive marker genes, suggest that jasmonate-mediated signaling may be associated with Foc TR4 resistance and collectively play a role in defense against Foc TR4. This study provides a valuable foundation for further elucidating the molecular mechanisms underlying Fusarium wilt resistance and for developing disease-resistant banana cultivars.