Identification, characterization and putative function of HvRin4, a barley homolog of Arabidopsis Rin4

RIN4 is a signaling molecule that plays a key role in disease resistance responses in plants. Barley RIN4 (HvRIN4) was first identified as an interactor of the stem rust resistance protein RPG1 in a yeast two-hybrid system. Therefore, we isolated, characterized and studied HvRIN4 role in barley. Yeast two hybrid analysis, employing several deletion mutants of HvRIN4 revealed that the C-terminal end and a partial deletion of N-terminal end of HvRIN4 are important for interacting with RPG1. HvRIN4 interactions with RPG1 mutated proteins, which inactivate autophosphorylation, suggested that autophosphorylation or the amino acids required for autophosphorylation of RPG1 are essential for interaction.

► HvRin4 was isolated from barley and structurally characterized.
► HvRin4 expression is up-regulated by stem rust infection, independent of Rpg1 and pathogen virulence.
► C-terminal and part of N-terminal of HvRIN4 are important for interaction with RPG1.
► Mutations that inactivate RPG1 autophosphorylation fail to interact with HvRIN4 suggesting that phosphorylation is required.
► Mutations in two kinase domains of RPG1 that lead to susceptibility against stem rust, also fail to interact with HvRIN4.