Molecular cloning and defence functional analysis of MaNPR11 from Cavendish banana (Musa spp.)

Bananas (Musa spp.) are globally critical economic crops, but the commercially dominant Cavendish cultivars are highly susceptible to Fusarium oxysporum f. sp. cubense (Foc), a destructive soil-borne pathogen. It severely undermines the healthy and sustainable advancement of the banana industry. Systemic acquired resistance (SAR) mediated by NPR1 (Nonexpressor of Pathogenesis-Related Genes 1) is a key plant defense mechanism, yet the role of banana NPR1 homologs stays unclear. Here, we cloned a NPR1-like gene, MaNPR11, from BaXi jiao (BX, Musa spp. AAA cv. Cavendish), which was suppressed in susceptible cv. BX but significantly up-regulated in resistant cv. GCTCV-119. Besides, protein-protein interaction assays ascertained that MaNPR11 interacted with 5 MaTGAs in the nucleus. Furthermore, transient overexpression of the MaNPR11 gene in banana increased the expression levels of immunity-related genes (MaMAPK, MaPAL, and MaPR3), ethylene synthesis-related gene (MaACO) and MaTGA4, while decreased the level of reactive oxygen species (ROS)-related gene (MaRBOH). Notably, overexpression of the MaNPR11 gene in tobacco significantly strengthened resistance to Fusarium oxysporum f. sp. nicotianae by promoting the expression of several genes involved in PR and ROS scavenging-related genes. Therefore it is speculated that MaNPR11 may positively regulates banana resistance to Fusarium oxysporum f. sp. cubense Tropical Race 4 (Foc TR4) by interacting with MaTGA4 and modulating salicylic acid (SA), ethylene (ET), and ROS signaling pathways, serving as a candidate target for disease resistance genetic improvement.