Two different CC-NBS-LRR genes are required for Lr10-mediated leaf rust resistance in tetraploid and hexaploid wheat.
Comparative 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.
Loutre
Caroline
C
Institute of Plant Biology, University of Zurich, Zollikerstrasse 107, 8008 Zürich, Switzerland.
Wicker
Thomas
T
Travella
Silvia
S
Galli
Paolo
P
Scofield
Steve
S
Fahima
Tzion
T
Feuillet
Catherine
C
Keller
Beat
B
D000483:Alleles; D000595:Amino Acid Sequence; D018744:DNA, Plant / Q000235:genetics; D020868:Gene Silencing; D017343:Genes, Plant; D014644:Genetic Variation; D007113:Immunity, Innate; D008969:Molecular Sequence Data; D010935:Plant Diseases / Q000235:genetics*; D011123:Polyploidy; D012641:Selection, Genetic; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014908:Triticum / Q000235:genetics* / Q000378:metabolism
D018744:DNA, Plant