Involved in defense responses (PubMed:19696351, PubMed:26740780). Contributes to slowing defense responses toward Magnaporthe oryzae (PubMed:19696351). By Magnaporthe oryzae. The pi21 allele confers an improved non-race-specific blast resistance toward Magnaporthe oryzae (PubMed:19696351). Reduced salicylic acid (SA) responses (e.g. WRKY45 expression) but increased systemic acquired response (SAR, e.g. PR1b and PBZ1 accumulation), jasmonic acid (JA, e.g. JAmyb expression) and abscisic acid (ABA, e.g. SalT expression) responses in response to M.oryzae spores (PubMed:26740780).