Quantitative proteomic analyses reveal that RBBI3.3, a trypsin inhibitor protein, plays an important role in Magnaporthe oryzae infection in rice

Magnaporthe oryzae (M. oryzae) is the causative agent of rice blast, the most destructive rice disease in China. This study was designed to ascertain the molecular mechanisms of the response of rice to M. oryzae infection to facilitate the breeding of new high-quality and disease-resistant rice varieties using isobaric tags for relative and absolute quantification (iTRAQ) combined with a high-throughput mass spectrometry identification platform. M. oryzae infection models were constructed with the resistant rice cultivar Gumei2 and the non-resistant cultivar Lijiangxintuanheigu (LTH). The results showed that total of 1541 proteins were identified, among which 843 proteins were overlapping between the two biological replicates analyses. Seventy-one proteins were classified as fungi-responsive. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses revealed the important roles of these proteins in metabolic processes. Detailed phenotypic analyses revealed that the trypsin inhibitor RBBI3.3 was effective in inhibiting the initial formation of appressoria. Our quantitative proteomic study provides insights into the molecular mechanism underlying M. oryzae resistance in the incompatible rice Gumei2. The identification of RBBI3.3 as a key defense regulator highlights a new possibility for disease control.