Two different CC‐NBS‐LRR genes are required for Lr10‐mediated leaf rust resistance in tetraploid and hexaploid wheat

Abstract

SUMMARYComparative study of disease resistance genes in crop plants and their relatives provides insight on resistance gene function, evolution and diversity. Here, we studied the allelic diversity of the Lr10 leaf rust resistance gene, a CC-NBS-LRR coding gene originally isolated from hexaploid wheat, in 20 diploid and tetraploid wheat lines. Besides a gene in the tetraploid wheat variety 'Altar' that is identical to the hexaploid wheat Lr10, two additional, functional resistance alleles showing sequence diversity were identified by virus-induced gene silencing in tetraploid wheat lines. In contrast to most described NBS-LRR proteins, the N-terminal CC domain of LR10 was found to be under strong diversifying selection. A second NBS-LRR gene at the Lr10 locus, RGA2, was shown through silencing to be essential for Lr10 function. Interestingly, RGA2 showed much less sequence diversity than Lr10. These data demonstrate allelic diversity of functional genes at the Lr10 locus in tetraploid wheat, and these new genes can now be analyzed for agronomic relevance. Lr10-based resistance is highly unusual both in its dependence on two, only distantly, related CC-NBS-LRR proteins, as well as in the pattern of diversifying selection in the N-terminal domain. This indicates a new and complex molecular mechanism of pathogen detection and signal transduction.

Evolution and Adaptation of Wild Emmer Wheat Populations to Biotic and Abiotic Stresses

“…This gene has a single copy on chromosome 1AS and is present in all three ploidy levels of the Triticum genus. Two different CC-NBS-LRR coding genes, Lr10 and closely linked RGA2, are required for Lr10-mediated leaf rust resistance (77). An analysis of 54 Lr10 sequences revealed 33 different haplotypes and very high nucleotide diversity (π = 0.029) among DIC natural populations in Israel (120).…”

The Rice Resistance Protein Pair RGA4/RGA5 Recognizes the Magnaporthe oryzae Effectors AVR-Pia and AVR1-CO39 by Direct Binding

“…For instance, an increasing number of resistances mediated by pairs of distinct NB-LRR proteins have been described. Pairs of resistance proteins can be formed by two TIR-NB-LRR proteins, as in the case of RPS4 and RRS1 mediating multiple resistances in Arabidopsis (Gassmann et al, 1999;Deslandes et al, 2002;Birker et al, 2009;Narusaka et al, 2009) or by two CC-NB-LRR proteins, such as Lr10 and RGA2, mediating resistance against wheat leaf rust caused by Puccinia triticina (Loutre et al, 2009). The functional interaction of one CC-NB-LRR and one TIR-NB-LRR protein has also been described in the case of RPM1 and TAO1 (Eitas et al, 2008).…”

Diagnostic value of molecular markers for Lr genes and characterization of leaf rust resistance of German winter wheat cultivars with regard to the stability of vertical resistance

“…Lr34 ) and Lr46 (Singh et al 1998) which are not associated with a hypersensitive reaction. The isolation and molecular characterization of Lr1 (Cloutier et al 2007), Lr10 (Loutre et al 2009) and Lr21 (Huang and Gill 2001), as race specific coiled coil-nucleotide-binding siteleucine-rich repeats coding genes, explains the higher durability of Lr34 which is a race unspecific adenosine triphosphate-binding cassette-transporter ).…”