Function of the rice gp91phox homologs OsrbohA and OsrbohE genes in ROS-dependent plant immune responses

Abstract

Reactive oxygen species (ROS) are proposed to function as diffusible signaling molecules in plant immune response. Rice respiratory burst oxidase homologs (Osrboh genes) are proposed to play a role in ROS generation. We examined a role in rice immune responses of four Osrboh homologs, OsrbohA, OsrbohB, OsrbohD, and OsrbohE. OsrbohA and OsrbohD transcripts were induced after inoculation with an incompatible N1141 strain of Acidovorax avenae, whereas OsrbohaB and OsrbohE mRNA levels did not obviously change even after inoculation with the incompatible strain. We examined the function of the Osrboh genes in ROS generation and in the plant immune response using RNAi-based knockdown in rice cells. OsrbohA and OsrbohE knockdown lines showed that rapid H 2 O 2 generation is caused by OsrbohA, whereas OsrbohE is involved in late H 2 O 2 production during the immune response. Hypersensitive cell death was decreased only in the OsrbohA knockdown line. We further demonstrated that among immune related genes, the induction of EL2 and LOX genes is controlled by ROS generated by OsrbohE, whereas expression of Cht-1 gene is regulated by both OsrbohA and OsrbohE. These results indicate that the ROS molecules generated by OsrbohA and OsrbohE regulate different signaling pathways in the plant immune response. the Arabidopsis genome (Foreman et al. 2003). Of these rboh in Arabidopsis, AtrbohD and AtrbohF were shown to be necessary for ROS generation in the plant immune responses (Torres et al. 2002). Furthermore, NtbohD from Nicotiana tabacum and NbrbohA and NbrbohB from N. benthamiana were required for ROS accumulation and resistance (Simon-Plas et al. 2002;Yoshioka et al. 2003), suggesting that individual isoforms have different functions and participate in multiple distinct signaling pathways.Acidovorax avenae is a Gram-negative bacterium that causes a seedling disease characterized by the formation of brown stripes on the sheaths of infected plants (Kadota et al. 1991). A. avenae can infect a wide range of monocotyledonous plants, including rice, oats, Italian millet, and maize. However, individual strains of the pathogen can infect only one or a few host species (Nishiyama et al. 1979;Kadota et al. 1991;Kadota et al. 1996). We recently reported that several immune responses, such as H 2 O 2 generation, hypersensitive cell death accompanied by clear 180-bp nucleosomal DNA laddering, and immune-related genes were induced when cultured rice cells were inoculated with a riceincompatible strain of A. avenae. These responses were completely abolished when a rice-compatible strain of A. avenae was used as the inoculating pathogen (Che et al. 1999;Tanaka et al. 2001;Iwano et al. 2002;Tanaka et al. 2003;Fujiwara et al. 2004). To identify the specific elicitor related to the induction of these immune responses in cultured rice cells, a strain-specific antibody was raised against the incompatible strain (N1141) and then absorbed by the compatible strain (H8301). The specific antibody detected flagellin protein, a component of t...

Calcium-Dependent Protein Kinases Regulate the Production of Reactive Oxygen Species by Potato NADPH Oxidase

“…RBOH was first isolated from rice (Oryza sativa) as a homolog of gp91 phox (Groom et al, 1996) and then identified in various plant species (Keller et al, 1998;Torres et al, 1998;Amicucci et al, 1999;Yoshioka et al, 2001Yoshioka et al, , 2003Yoshie et al, 2005). Earlier work has shown that RBOH is a main component in ROS production during biotic and abiotic stresses.…”

Production Sites of Reactive Oxygen Species (ROS) in Organelles from Plant Cells

“…Thus, the integral plasma membrane protein is composed of six transmembrane domains (TMD-1 to TMD-6) connected by five loops (loops A-E) where TMD-3 and TMD-5 contain pairs of His residues required to bind two heme groups, C-terminal FAD and NADPH hydrophilic domains, and two N-terminal calcium-binding (EF-hand) motifs and some phosphorylation target sites (Yoshie et al 2005;Marino et al 2012) (Fig. 3).…”

Involvement of mitogen-activated protein kinase in the induction of StrbohC and StrbohD genes in response to pathogen signals in potato

“…Group III contains NbrbohB, StrbohB, NtrbohD, AtrbohD and AtrbohF whose transcription is induced by biotic stress (Desikan et al 1998;Yoshioka et al 2001Yoshioka et al , 2003Simon-Plas et al 2002;Kwak et al 2003). Group IV contains defense-related OsrbohE, but the gene is not induced by pathogen attack (Yoshie et al 2005). Both StrbohC and StrbohD were classified into Group III, a cluster containing many of inducible genes.…”

“…Group II includes NbrbohA, StrbohA and Lerboh1, which are constitutively expressed in tobacco, potato and tomato plants, respectively. This group also contains rice OsrbohA and OsrbohD, which are induced by a pathogen (Yoshie et al 2005). Group III contains NbrbohB, StrbohB, NtrbohD, AtrbohD and AtrbohF whose transcription is induced by biotic stress (Desikan et al 1998;Yoshioka et al 2001Yoshioka et al , 2003Simon-Plas et al 2002;Kwak et al 2003).…”

“…Several lines of evidence indicate that NADPH oxidase may play a pivotal role in defense responses. Homologs of gp91 phox (respiratory burst oxidase homolog [rboh]), which is the catalytic subunit of phagocyte NADPH oxidase, have been isolated from several higher plants (Groom et al 1996;Keller et al 1998;Torres et al 1998;Amicucci et al 1999;Yoshioka et al 2001;Yoshie et al 2005). The silencing genes NbrbohA and NbrbohB in Nicotiana benthamiana leaves decreased ROS production in response to treatment with INF1 elicitor and to infection by an avirulent race of Phytophthora infestans and disrupted resistance to the pathogen .…”