Genome-Wide Analysis of the Banana NBS Gene Family and Expression Profiling of the Fusarium Wilt Resistance Gene MamRGA2 in Response to Defense-Related Phytohormones

Background/Objectives: Banana (Musa spp.) production is severely threatened by Fusarium wilt caused by Fusarium oxysporum f. sp. cubense tropical race 4 (Foc TR4), highlighting the need to identify genetic determinants of resistance. Methods: We performed a genome-wide analysis of NBS genes in Musa acuminata ssp. malaccensis, including phylogenetic, chromosomal, and microsynteny analyses. The genomic context and promoter regions of MamRGA2 were characterized, its response to defense-related phytohormones was evaluated by RT-qPCR, and its protein structure was predicted by homology modeling. Results: A total of 118 NBS genes were identified. Notably, we report for the first time in banana two NBS genes encoding proteins with integrated domains, corresponding to an ATP-binding cassette (ABC) transporter and a Nuclear Factor Y subunit A (NF-YA) transcription factor. Chromosomal mapping revealed a marked enrichment of NBS genes on chromosome 3, which harbors MamRGA2, an NBS gene associated with resistance to Foc TR4. RT-qPCR analyses showed that MamRGA2 is strongly induced by exogenous methyl jasmonate (MeJA) in the resistant wild genotype but not in a susceptible Cavendish cultivar, a pattern associated with divergence in promoter sequences between the two genotypes. Structural modeling suggested that the MamRGA2 protein possesses features consistent with a resistosome-like architecture. Conclusions: Overall, these findings expand current knowledge of NBS gene diversity in banana and provide a framework for future studies aimed at elucidating the molecular mechanisms underlying resistance to Foc TR4.