Rice Hypersensitive Induced Reaction Protein 1 (OsHIR1) associates with plasma membrane and triggers hypersensitive cell death

Abstract

BackgroundIn plants, HIR (Hypersensitive Induced Reaction) proteins, members of the PID (Proliferation, Ion and Death) superfamily, have been shown to play a part in the development of spontaneous hypersensitive response lesions in leaves, in reaction to pathogen attacks. The levels of HIR proteins were shown to correlate with localized host cell deaths and defense responses in maize and barley. However, not much was known about the HIR proteins in rice. Since rice is an important cereal crop consumed by more than 50% of the populations in Asia and Africa, it is crucial to understand the mechanisms of disease responses in this plant. We previously identified the rice HIR1 (OsHIR1) as an interacting partner of the OsLRR1 (rice Leucine-Rich Repeat protein 1). Here we show that OsHIR1 triggers hypersensitive cell death and its localization to the plasma membrane is enhanced by OsLRR1.ResultThrough electron microscopy studies using wild type rice plants, OsHIR1 was found to mainly localize to the plasma membrane, with a minor portion localized to the tonoplast. Moreover, the plasma membrane localization of OsHIR1 was enhanced in transgenic rice plants overexpressing its interacting protein partner, OsLRR1. Co-localization of OsHIR1 and OsLRR1 to the plasma membrane was confirmed by double-labeling electron microscopy. Pathogen inoculation studies using transgenic Arabidopsis thaliana expressing either OsHIR1 or OsLRR1 showed that both transgenic lines exhibited increased resistance toward the bacterial pathogen Pseudomonas syringae pv. tomato DC3000. However, OsHIR1 transgenic plants produced more extensive spontaneous hypersensitive response lesions and contained lower titers of the invading pathogen, when compared to OsLRR1 transgenic plants.ConclusionThe OsHIR1 protein is mainly localized to the plasma membrane, and its subcellular localization in that compartment is enhanced by OsLRR1. The expression of OsHIR1 may sensitize the plant so that it is more prone to HR and hence can react more promptly to limit the invading pathogens' spread from the infection sites.

Overexpression of BAX INHIBITOR-1 Links Plasma Membrane Microdomain Proteins to Stress

“…S2). Several members of this plant-specific subclass have been characterized as localized to PM microdomains and responsive to disease and osmotic stresses (Nohzadeh Malakshah et al, 2007;Jung et al, 2008;Yu et al, 2008;Zhou et al, 2009Zhou et al, , 2010Choi et al, 2011;Qi et al, 2011).…”

Functional roles of the pepper leucine-rich repeat protein and its interactions with pathogenesis-related and hypersensitive-induced proteins in plant cell death and immunity

“…Overexpression of AtHIR1 and AtHIR2, and rice OsHIR1 in Arabidopsis enhances resistance to virulent P. syringae pv. tomato infection, but an enhanced susceptibility to necrotrophic pathogens could not be excluded (Zhou et al 2010;Qi et al 2011). By contrast, CaHIR1 silencing distinctly disrupts hypersensitive and susceptible cell death in pepper plants ).…”

“…HIR genes have been identified in plant cell death and defense responses to biotic and abiotic stresses in several plant species, including tobacco, maize, barley, rice, wheat, pepper, soybean, and Arabidopsis (Karrer et al 1998;Nadimpalli et al 2000;Rostoks et al 2003;Jung and Hwang 2007;Yu et al 2008;Zhou et al 2009Zhou et al , 2010Qi et al 2011;Xiang et al 2015). The three maize HIR genes Zm-hir1, Zm-hir2, and Zm-hir3 share strong sequence homology with NG1 (Nadimpalli et al 2000).…”

“…Rice OsHIR1 is induced in rice leaves by Xanthomonas oryzae pv. oryzae infection (Zhou et al 2010). Defense responses activated by the OsHIR1-OsLRR1 protein complex are well documented in rice plants during X. oryzae pv.…”

“…Rice OsLRR1 interacts with OsHIR1, which is localized at the plasma membrane (Zhou et al 2009). OsHIR1 triggers hypersensitive cell death, and its localization to the plasma membrane is enhanced by OsLRR1 (Zhou et al 2010), which suggests that OsLRR1 acts as a positive regulator for OsHIR1 function.…”