Identification of the NBS-LRR gene family and AkNBS-LRR43 and 100 functional analysis under biotic stress

AkNBS-LRR43 and AkNBS-LRR100 positively regulate immunity in Amorphophallus konjac against Pectobacterium carotovorum subsp. carotovorum by enhancing antioxidant activity and reducing oxidative damage. Amorphophallus konjac, an economically important Araceae species rich in konjac glucomannan (KGM), faces production losses from biotic/abiotic stresses. Nucleotide-binding-site leucine-rich repeat (NBS-LRR) genes, crucial for plant immunity, remain understudied in A. konjac. Here, we comprehensively analyzed 146 AkNBS-LRR genes, characterizing their structure, chromosomal distribution, phylogeny, cis-elements and expression patterns. Furthermore, two candidate genes (AkNBS-LRR43/100) were functionally validated. The AkNBS-LRRs showed chromosomal preference (chr1/2/3/5/9/11) and clustered into five phylogenetic subclasses (CNL_E predominant). These genes harbored abundant cis-elements associated with growth and stress responses. Functional annotation implicated their roles in signal transduction, development, and biotic/abiotic stress responses. Transcriptome profiling revealed pathogen-responsive differential expression patterns. RT-qPCR revealed differential AkNBS-LRR expression during Pectobacterium carotovorum subsp. carotovorum (Pcc) infection, with AkNBS-LRR43/100 showing pronounced upregulation. Subcellular localization confirmed their nuclear targeting. Transgenic A. konjac plants transiently overexpressing AkNBS-LRR43/100 showed significantly reduced lesion expansion under pathogen infection compared to controls. Concurrently, these transgenic plants exhibited increased activities of peroxidase (POD) and superoxide dismutase (SOD), along with decreased malondialdehyde (MDA) content, which may lead to enhanced reactive oxygen species (ROS) scavenging capacity and consequently to reduced disease symptom development. These findings suggest that AkNBS-LRR43/100 may function as positive regulators in A. konjac disease resistance by enhancing antioxidant capacity.