Rpr1, a gene required for Rpg1-dependent resistance to stem rust in barley

Area of Science:

• Plant Science
• Genetics
• Molecular Biology

Background:

• Stem rust, caused by Puccinia graminis f. sp. tritici, poses a significant threat to barley production.
• The Rpg1 gene provides resistance to many stem rust pathotypes in barley.
• A mutant susceptible to stem rust pathotype Pgt-MCC was identified in barley cv. Morex, which carries Rpg1.

Purpose of the Study:

• To identify and characterize the genetic basis of susceptibility in the rpr1 mutant.
• To investigate the role of Rpr1 in Rpg1-mediated stem rust resistance.
• To understand the molecular mechanisms underlying Rpg1 function.

Main Methods:

• Genetic analysis and Rpg1 mRNA/protein expression analysis.
• Genome-wide expression profiling using the Affymetrix Barley1 GeneChip.
• Genomic PCR, RT-PCR, and Southern analyses to identify gene deletions.

Main Results:

• A mutation, designated Rpr1 (Required for P. graminis resistance), was identified as a suppressor of Rpg1.
• Rpr1 is not required for Rpg5- and rpg4-mediated resistance, indicating pathway specificity.
• Three genes (Contig4901_s_at, HU03D17U_s_at, Contig7061_s_at) were deleted in the rpr1 mutant and mapped to chromosome 4(4H) bin 5.

Conclusions:

• The loss of stem rust resistance in the rpr1 mutant is likely due to the deletion of one or more of the identified genes.
• Rpr1 plays a crucial role specifically in the Rpg1-mediated stem rust resistance pathway.
• Further investigation is needed to confirm the exact gene(s) responsible for the susceptible phenotype within the deleted region.