Novel Positive Regulatory Role for the SPL6 Transcription Factor in the N TIR-NB-LRR Receptor-Mediated Plant Innate Immunity

Following the recognition of pathogen-encoded effectors,plant tir-nb-lrr immune receptors induce defense signaling by a largely unknown mechanism. we identify a novel and conserved role for the squamosa promoter binding protein (sbp)-domain transcription factor spl6 in enabling the activation of the defense transcriptome following its association with a nuclear-localized immune receptor. during an active immune response,the nicotiana tir-nb-lrr n immune receptor associates with nbspl6 within distinct nuclear compartments. nbspl6 is essential for the n-mediated resistance to tobacco mosaic virus. similarly,the presumed arabidopsis ortholog atspl6 is required for the resistance mediated by the tir-nb-lrr rps4 against pseudomonas syringae carrying the avrrps4 effector. transcriptome analysis indicates that atspl6 positively regulates a subset of defense genes. a pathogen-activated nuclear-localized tir-nb-lrr like n can therefore regulate defense genes through spl6 in a mechanism analogous to the induction of mhc genes by mammalian immune receptors like ciita and nlrc5. © 2013 padmanabhan et al.