Functional analysis of plant immune regulator OsPti1a in rice

An understanding of plant immune systems is important for crop breeding with enhanced disease resistance against pathogen infection. Previous studies reveal that plant has evolved two types of defense mechanisms, which are called “basal resistance” and “R‒gene mediated resistance”, for protecting thewrselves from pathogen attack. Recent studies suggest that both defense systems use a common pathway to activate defense responses, however, the downstream components in both pathways are still obscure. OsPto-interacting protein 1a (OsPti1a), which is a functional ortholog of tomato Pti1, negatively regulates both basal resistance and R‒gene mediated resistance in rice. ospti1a mutant shows lesion formation and accompanying defense responses without pathogen infection. OsPti1a is phosphorylated by upstream kinase oxidative signal inducible1 (OsOxi1) and the phosphorylation of OsPti1a has an important role in activating basal resistance against pathogen infection. Additionally, OsOxi1 is phosphorylated by upstream kinase 3‒phosphoinotiside-dependent protein kinase 1 (OsPdk1). OsPdk1 has an important role for activating basal resistance against compatible pathogen infection. Therefore, OsPdk1-OsOxi1-OsPti1a phosphorylation cascade regulates proper activation of basal resistance in rice. Interestingly, OsPti1a localizes at plasma membrane, and cellular localization of OsPti1a has an important function in suppvessing lesion formation. Especially, N‒terminal amino acid sequences of OsPti1a have a post-translational modification for binding to plasma membrane. Further, OsPti1a forms complexes with potentially plant immune related proteins at plasma membrane, suggesting that plasma membrane localized OsPti1a probably regulates plant immune complex through its phosphorylation during pathogen infection