Functional divergence of duplicated genes results in a novel blast resistance gene Pi50 at the Pi2/9 locus

Abstract

We characterized a novel blast resistance gene Pi50 at the Pi2/9 locus; Pi50 is derived from functional divergence of duplicated genes. The unique features of Pi50 should facilitate its use in rice breeding and improve our understanding of the evolution of resistance specificities. Rice blast disease, caused by the fungal pathogen Magnaporthe oryzae, poses constant, major threats to stable rice production worldwide. The deployment of broad-spectrum resistance (R) genes provides the most effective and economical means for disease control. In this study, we characterize the broad-spectrum R gene Pi50 at the Pi2/9 locus, which is embedded within a tandem cluster of 12 genes encoding proteins with nucleotide-binding site and leucine-rich repeat (NBS-LRR) domains. In contrast with other Pi2/9 locus, the Pi50 cluster contains four duplicated genes (Pi50_NBS4_1 to 4) with extremely high nucleotide sequence similarity. Moreover, these duplicated genes encode two kinds of proteins (Pi50_NBS4_1/2 and Pi50_NBS4_3/4) that differ by four amino acids. Complementation tests and resistance spectrum analyses revealed that Pi50_NBS4_1/2, not Pi50_NBS4_3/4, control the novel resistance specificity as observed in the Pi50 near isogenic line, NIL-e1. Pi50 shares greater than 96 % amino acid sequence identity with each of three other R proteins, i.e., Pi9, Piz-t, and Pi2, and has amino acid changes predominantly within the LRR region. The identification of Pi50 with its novel resistance specificity will facilitate the dissection of mechanisms behind the divergence and evolution of different resistance specificities at the Pi2/9 locus.

Improving of Rice Blast Resistances in Japonica by Pyramiding Major R Genes

“…Using host resistance has been proven to be the most effective and economical method to control rice blast (Fukuoka et al, 2009). So far, 102 rice blast R genes have been identified (Su et al, 2015; Vasudevan et al, 2015; Zheng et al, 2016). Among them, 27 genes have been cloned: Pib, Pb1 , Pita , Pi9 , Pi2 , Pizt , Pid2 , Pi33 , Pii , Pi36 , Pi37 , Pikm , Pit , Pi5 , Pid3 , Pid3-A4 , Pi54 , Pish , Pik , Pikp , Pia , PiCO39 , Pi25 , Pi1 , Pi21 , P50 and Pi65(t) (Liu et al, 2014; Su et al, 2015; Zheng et al, 2016).…”

“…So far, 102 rice blast R genes have been identified (Su et al, 2015; Vasudevan et al, 2015; Zheng et al, 2016). Among them, 27 genes have been cloned: Pib, Pb1 , Pita , Pi9 , Pi2 , Pizt , Pid2 , Pi33 , Pii , Pi36 , Pi37 , Pikm , Pit , Pi5 , Pid3 , Pid3-A4 , Pi54 , Pish , Pik , Pikp , Pia , PiCO39 , Pi25 , Pi1 , Pi21 , P50 and Pi65(t) (Liu et al, 2014; Su et al, 2015; Zheng et al, 2016). The majority of rice blast R genes are associated with a HR according to the gene-for-gene concept, and race specificity is the key feature of this R gene-mediated disease resistance (Fukuoka et al, 2009).…”

Dissection of broad-spectrum resistance of the Thai rice variety Jao Hom Nin conferred by two resistance genes against rice blast

“…Some are clustered on a gene family (Sharma et al 2012). Many allelic genes have been reported, for example Pish/Pi35 on chromosome 1 (Takahashi et al 2010; Fukuoka et al 2014), Pi9/Pi2/Pizt/Pi50 on chromosome 6 (Qu et al 2006; Zhou et al 2006; Su et al 2015), Pi5/Pii on chromosome 9 (Lee et al 2009; Takagi et al 2013), and Pikh/Pikm/Pik/Pikp/Pi1 on chromosome 11 (Ashikawa et al 2008; Xu et al 2008; Yuan et al 2011; Zhai et al 2011; Hua et al 2012). To date, 11 avirulence ( Avr ) genes in rice blast fungus have been cloned.…”

“…The presence of even only one R gene can induce resistance to many isolates of M. oryzae (Qu et al 2006). Many broad-spectrum R genes have been validated such as Pi9 (Qu et al 2006), Pi2 , Piz-t (Zhou et al 2006), Pi40 (t) (Jeung et al 2007), Pi20 (t) (Li et al 2008), Pi5 (Lee et al 2009), Pi1 (Hua et al 2012), Pi54rh (Das et al 2012), Pi56 (t) (Liu et al 2013), and Pi50 (Su et al 2015). Unfortunately, the resistance controlled by most race-specific R genes is prone to collapse often in a few years after introduction to the rice field due to the quick adaptation of rice blast pathogen (Kiyosawa 1982; Fukuoka et al 2009).…”

Marker‐assisted selection for rice blast resistance genes Pi2 and Pi9 through high‐resolution melting of a gene‐targeted amplicon

“…, Su et al. ). These four allelic R genes, Pi2 , Piz‐t and Pi50 were isolated from Oryza sativa , while the Pi9 was originated from Oryza minuta .…”