Submitted to: Plant and Animal Genome Conference Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 1/15/2005
Publication Date: 1/15/2005
Citation: Caldo, R.A., Nettleton, D., Wise, R.P. 2005. Induction of basal defense differentiates rapid and delayed host-specific barley resistance to powdery mildew. Plant and Animal Genome XIII Conference Proceedings. P665.
Technical Abstract: Non-self recognition is an indispensable system in plants to prevent microbial attack. Perception of pathogen-derived general elicitors triggers basal defense, while direct or indirect recognition of avirulence gene product triggers host-specific defense. In barley, powdery mildew resistance is controlled by Mla genes and characterized into rapid, intermediate, and slow infection phenotypes. In this study, we analyzed the mRNA expression of basal-defense related genes in barley lines containing powdery mildew resistance genes (Mla1, Mla6, and Mla12) and their mutants. In rapid resistance controlled by Mla1 and Mla6, there was a steady hyper-accumulation of basal defense-related transcripts from 0 to 16 hai. However, in delayed resistance controlled by Mla12, an early hyper-induction of the selected transcripts from 0 to 8 hai was observed, but with suppression of the mRNA accumulation at 16 hai. This result suggests that basal defense needs to be suppressed to allow the formation of haustoria in the infected cells in delayed resistance, which may cause the plant to trigger cell death in the surrounding cells to inhibit further growth of the fungal pathogen. Thus, modulation of transcript accumulation of the basal defense-related genes at the early stages of infection differentiates the mechanisms of Mla-specified rapid and delayed resistance to powdery mildew.