An Oryza Specific Hydroxycinnamoyl Tyramine Gene Cluster Contributes to Enhanced Disease Resistance

Abstract Genomic clustering of non-homologous genes for the biosynthesis of plant defensive compounds is an emerging theme, but insight into their formation and physiological function remains limited. Here we report the identification of a newly discovered hydroxycinnamoyl tyramine (HT) gene cluster in rice which contains a pyridoxamine 5\u0027-phosphate oxidase producing cofactor PLP (pyridoxal phosphate), a PLP-dependent tyramine decarboxylase (OsTyDC1) and two duplicated hydroxycinnamoyl transferases (OsTHT1 and OsTHT2), and these members combined to represent an enzymological innovation gene cluster. Natural variation analysis shows that the abundance of the toxic gene cluster intermediate tyramine among different rice accessions are mainly determined by the coordinated transcription of OsTyDC1 and OsTHT1. Further pathogen incubation assays demonstrate that the end-products of HT gene cluster display enhanced resistance to both the bacterial pathogen Xanthomonas oryzae pv. oryzae (Xoo) and fungal pathogen Magnaporthe oryzae (M. oryzae), and the enhanced resistance is associated with the boost of phytoalexins and the activation of defense response. The unique presence of HT gene cluster in Oryza AA genome, together with the enrichment of transposon elements (TEs) within this gene cluster region provide an evolutionary background to accelerate cluster members combinations. Our study not only discover a gene cluster involved in the phenylpropanoid metabolism, but also addresses the key aspects of gene cluster formation and provides a new metabolic pool for plant defense against pathogens.