Characterization of rice and maize CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5 in plant immunity

Rice and maize are two of the world’s most productive crops. Their production is often severely threatened by devastating pathogens. As a key negative immune regulator, CONSTITUTIVE EXPRESSER OF PATHOGENESIS-RELATED GENES 5 (CPR5) has been characterized well in dicots but not in monocots. Here we took advantage of Arabidopsis cpr5 mutants to explore the functional conservation of its counterparts from the monocots rice and maize. A single copy of the CPR5 gene is present in the Arabidopsis genome, while two copies of it are identified in the genomes of both rice and maize. Like the Arabidopsis CPR5 protein, all those from rice and maize have an RNA recognition motif in the N-terminal region and five transmembrane domains in the C-terminal region. The 35S promoter-driven coding DNA sequences of four CPR5 genes from rice and maize were introduced into an Arabidopsis cpr5 mutant. The results showed that cpr5 -induced immunity and programmed cell death were fully suppessed by these genes, indicating that the function of CPR5 proteins are conserved between dicots and monocots. Intriguingly, we showed that mutations of the CPR5 gene on chromosome I but not the other on chromosome II confer resistance to rice yellow mottle virus in African rice, suggesting that these two copies of rice CPR5 proteins have a distinctive role in immunity. These findings will provide a basis for application of CPR5 to improve disease resistance in monocot crops.