Isolation and Expression of an NBS-LRR Protein-encoding Resistance Gene Candidate that Segregates with a Rust Resistance Gene in Sunflower

Abstract

Sunflower rust caused by Puccinia helianthi is considered to be a major disease of sunflower because it causes significant yield losses. RACE-PCR was used to isolate a full-length cDNA of resistance gene candidate (RGC) 260, which segregated with the Radv resistance gene conferring resistance to rust. The predicted protein of this RGC is 1340 amino acids long and belongs to the CC-NBS-LRR subfamily of plant resistance genes. To verify that RGC260 belongs to a functional group of resistance genes, the transcript accumulation of the RGC was detected using real-time PCR following infection of plants with P. helianthi and Plasmopara halstedii, the two major pathogens of sunflower. The expression profile of this RGC revealed that its expression was specifically induced during an incompatible interaction between sunflower and P. helianthi. Expression profiles of defense genes and component signaling genes proposed the nature of this pathosystem as a gene-for-gene interaction. These results suggest that RGC260 may play a critical role in protecting sunflower cells against P. helianthi.