Deciphering the transcriptional regulation and spatiotemporal distribution of immunity response in barley to Pyrenophora graminea fungal invasion

Ahmed Ghannam, Houda Alek, Sanaa Doumani, Doureid Mansour, Mohamad I. E. Arabi

Barley leaf stripe disease, caused by the fungus Pyrenophora graminea (Pg), is a worldwide crop disease that results in significant loss of barley yield. The purpose of the present work was to use transcriptomic profiling to highlight barley genes and metabolic pathways affected or altered in response to Pg infection and consequently elucidate their involvement and contribution in resistance to leaf stripe. Our study examined and compared the transcriptomes of two barley genotypes using an established differential display reverse-transcription polymerase chain reaction (DDRT-PCR) strategy at 14 and 20 days post-inoculation (dpi). A total of 54 significantly modulated expressed sequence tags (ESTs) were identified. The analysis of gene expression changes during the course of infection with Pg suggested the involvement of 15 upregulated genes during the immunity response. By using network-based analyses, we could establish a significant correlation between genes expressed in response to Pg invasion. Microscopic analysis and quantitative PCR (qPCR) profiling of callose synthase and cellulose synthases revealed a direct involvement of cell wall reinforcement and callose deposition in the Pg-resistant phenotype. We have identified a number of candidate genes possibly involved in the host-pathogen interactions between barley and Pg fungus, 15 of which are specifically expressed in Pg-resistant plants. Collectively, our results suggest that the resistance to leaf stripe in barley proceeds through callose deposition and different oxidation processes.