Genome-wide identification and characterization of NBS-LRR gene family in tobacco (Nicotiana benthamiana)

Nicotiana benthamiana is an important model plant widely employed in plant virology, which involves the nucleotide binding site leucine-rich repeat (NBS-LRR) genes in disease resistance. In this study, firstly, 156 NBS-LRR homologs were identified by HMMsearch and they were divided into three clades in the phylogenetic tree by Clustal W, containing 5 TNL-type, 25 CNL-type, 23 NL-type, 2 TN-type, 41 CN-type, and 60 N-type proteins. Further, conserved motifs and domain composition were detected by MEME, showing 10 conserved motifs dispersed throughout the protein sequences in both typical- and irregular- type NBS-LRRs. Subcellular localization prediction by CELLO v.2.5 and Plant-mPLoc suggested 121 NBS-LRRs were located in cytoplasm, 33 in plasma membrane, and 12 in nucleus. And physicochemical characteristics by EXPASY ProtParam revealed common and unique features among the six types of NBS-LRR protein. Finally, gene structure analysis by TBtools exhibited most NBS-LRR genes were composed of either fewer or two introns. And regulatory cis-elements were assayed by PlantCARE, detecting 29 shared kinds and 4 kinds unique in irregular-type NBS-LRR genes, indicating potential upstream regulation factors. In summary, we provided important information on NBS-LRR genes and potential resources for improving disease resistance in tobacco, and will contribute to breeding programs for virus resistance.