Leaf rust resistance gene Lr1, isolated from bread wheat (Triticum aestivum L.) is a member of the large psr567 gene family

Abstract

In hexaploid wheat, leaf rust resistance gene Lr1 is located at the distal end of the long arm of chromosome 5D. To clone this gene, an F(1)-derived doubled haploid population and a recombinant inbred line population from a cross between the susceptible cultivar AC Karma and the resistant line 87E03-S2B1 were phenotyped for resistance to Puccinia triticina race 1-1 BBB that carries the avirulence gene Avr1. A high-resolution genetic map of the Lr1 locus was constructed using microsatellite, resistance gene analog (RGA), BAC end (BE), and low pass (LP) markers. A physical map of the locus was constructed by screening a hexaploid wheat BAC library from cultivar Glenlea that is known to have Lr1. The locus comprised three RGAs from a gene family related to RFLP marker Xpsr567. Markers specific to each paralog were developed. Lr1 segregated with RGA567-5 while recombinants were observed for the other two RGAs. Transformation of the susceptible cultivar Fielder with RGA567-5 demonstrated that it corresponds to the Lr1 resistance gene. In addition, the candidate gene was also confirmed by virus-induced gene silencing. Twenty T (1) lines from resistant transgenic line T (0)-938 segregated for resistance, partial resistance and susceptibility to Avr1 corresponding to a 1:2:1 ratio for a single hemizygous insertion. Transgene presence and expression correlated with the phenotype. The resistance phenotype expressed by Lr1 seemed therefore to be dependant on the zygosity status. T (3)-938 sister lines with and without the transgene were further tested with 16 virulent and avirulent rust isolates. Rust reactions were all as expected for Lr1 thereby providing additional evidence toward the Lr1 identity of RGA567-5. Sequence analysis of Lr1 indicated that it is not related to the previously isolated Lr10 and Lr21 genes and unlike these genes, it is part of a large gene family.

Unlocking wheat genetic resources for the molecular identification of previously undescribed functional alleles at the Pm3 resistance locus

“…Although VIGS has proven to be an effective method for several dicots (28), it is only recently that its successful use in monocots such as barley and wheat has been demonstrated. VIGS was shown to silence the barley phytoene desaturase gene (29) and was successfully used for silencing of leaf rust resistance genes Lr21 (30) and Lr1 (15). In our study, we found that VIGS was an effective strategy to assign function to the previously undescribed alleles.…”

“…10; N. Stein, et al, personal communication). Because the first wheat disease-resistance genes have been cloned (11)(12)(13)(14)(15)(16), the sequence information of these genes should allow the analysis of genetic diversity at these loci and the identification of new alleles through allele mining. Pm3, existing in 7 functionally distinct alleles (Pm3a to Pm3g), is the only wheat powdery mildew resistance gene cloned to date (13,14,16).…”

Virus-induced gene silencing and its application in plant functional genomics

“…Furthermore, LeMPK1, LeMPK2, and LeMPK3 are activated during the Cf-4/Avr4-induced HR [100]. Additionally, some genes related to defense responses and basal resistance against powdery mildew fungus [101,102], wheat leaf rust fungus [29,103], Colletotrichum destructivum, C. orbiculare [104], and tobacco blue mold fungus [105] have been identified in dicotyledonous or monocotyledonous plants.…”

RXLR-Mediated Entry of Phytophthora sojae Effector Avr1b into Soybean Cells Does Not Require Pathogen-Encoded Machinery

“…Many disease resistance genes that protect against fungal and oomycete pathogens also encode NBS-LRR proteins with a predicted intracellular location. Fungal resistance genes include the L, M, N, and P families of flax against flax rust (Lawrence et al, 1995;Anderson et al, 1997;Dodds et al, 2001aDodds et al, , 2001b, the rice (Oryza sativa) genes Pib (Wang et al, 1999), Pi-ta (Bryan et al, 2000), and Pi9 (Qu et al, 2006) against Magnaporthe grisea, the Mla resistance gene of barley (Hordeum vulgare) against the powdery mildew pathogen Blumeria graminis f. sp hordei (Halterman et al, 2001), the wheat (Triticum aestivum) Lr1 (Cloutier et al, 2007) and Lr10 (Feuillet et al, 2003) genes against leaf rust, and four alleles of the wheat Pm3 gene against powdery mildew (Yahiaoui et al, 2004;Srichumpa et al, 2005).…”