XA23 Is an Executor R Protein and Confers Broad-Spectrum Disease Resistance in Rice

Abstract

The majority of plant disease resistance (R) genes encode proteins that share common structural features. However, the transcription activator-like effector (TALE)-associated executor type R genes show no considerable sequence homology to any known R genes. We adopted a map-based cloning approach and TALE-based technology to isolate and characterize Xa23, a new executor R gene derived from wild rice (Oryza rufipogon) that confers an extremely broad spectrum of resistance to bacterial blight caused by Xanthomonas oryzae pv. oryzae (Xoo). Xa23 encodes a 113 amino acid protein that shares 50% identity with the known executor R protein XA10. The predicted transmembrane helices in XA23 also overlap with those of XA10. Unlike Xa10, however, Xa23 transcription is specifically activated by AvrXa23, a TALE present in all examined Xoo field isolates. Moreover, the susceptible xa23 allele has an identical open reading frame of Xa23 but differs in promoter region by lacking the TALE binding element (EBE) for AvrXa23. XA23 can trigger a strong hypersensitive response in rice, tobacco, and tomato. Our results provide the first evidence that plant genomes have an executor R gene family of which members execute their function and spectrum of disease resistance by recognizing the cognate TALEs in the pathogen.

Interfering TAL effectors of Xanthomonas oryzae neutralize R-gene-mediated plant disease resistance

“…To determine whether Xa1 , similar to Xa27 and other executor R genes15162122, recognizes TALEs through its promoter-specific transcription activation and iTALE overcomes resistance by suppressing Xa1 induction, we made a construct expressing Xa1 coding sequence under the promoter of a rice ubiquitin gene ( Os02g06640 ). The Ubi:Xa1 transgenic Kitaake lines ( n =4) were completely resistant to ΔTal3 and the resistance was suppressed in the presence of Tal3a (Supplementary Fig.…”

“…TALE-associated host R genes have been previously identified in rice ( Xa27 , Xa10 and Xa23 , xa13 , xa25 and xa41 ), tomato ( Bs4 ) and pepper ( Bs3 and Bs4C ); all of them, except one ( Bs4 ), have been found to be involved in transcriptional activation (dominant R gene) or lack thereof (recessive alleles of the otherwise S genes) by the cognate full-length TALEs141516222627282930. Bs4 , a constitutively expressed R gene encoding an NLR protein in tomato, activates resistance including HR in response to the full-length TALE AvrBs4, as well as mutants derived from various truncations of C terminus and truncations of large portion of central repetitive and C-terminal regions that lack the nuclear localization and transcription activation domains of AvrBs4, suggesting cytoplasmic perception of AvrBs4 by Bs4 in tomato1431.…”

A host basal transcription factor is a key component for infection of rice by TALE-carrying bacteria

“…TALE DNA-binding motifs have been detected in the promoters of some disease resistance genes, an apparent evolutionary response against TALE-carrying bacteria (Gu et al, 2005; Römer et al, 2010; Wang et al, 2015). Xoo TALE AvrXa23 activates the Xa23 resistance gene, resulting in resistance to Xoo (Wang et al, 2015).…”

“…Xoo TALE AvrXa23 activates the Xa23 resistance gene, resulting in resistance to Xoo (Wang et al, 2015). To investigate the role of TFIIAγ5 in Xa23 resistance, we crossed rice lines IRBB5, with a xa23 susceptibility and a TFIIAγ5 V39E resistance allele, and CBB23, with a Xa23 resistance and a TFIIAγ5 susceptibility allele.…”

Identification of novel recessive gene xa44(t) conferring resistance to bacterial blight races in rice by QTL linkage analysis using an SNP chip

“…In addition, three recessive R -genes xa15 , xa19 , and xa20 were induced in mutant lines (Vikal and Bhatia 2017), and two R -genes xa26 and xa28 were identified by genetic analysis (Lee et al 2003). To date, only nine R -genes have been isolated and cloned, including Xa1, Xa3/Xa26, xa5, Xa10, xa13, Xa21, Xa23, xa25 , and Xa27 , and five types of proteins are encoded by these genes (Gu et al 2004; Iyer and Mccouch 2004; Sun et al 2004; Liu et al 2011; Tian et al 2014; Wang et al 2015). Among these genes, three recessive R -genes have been characterized.…”