Nbrbohb Is Required For Resistance To Phytophthora Pathogens In Nicotiana Benthamiana

Phytophthora is subordinate to oomycete, which causes destructive diseases on plant. And the diseases lead billions of dollars losses around the world.Oomycete is evolutionarily distant from ’true’ fungi, common fungicides applied in fungi are unavailable for controlling the diseases caused by oomycete. Therefore learning the mechanism of the interaction between plant and Phytophthora will help researchers find new controlling strategies. Reactive oxygen species (ROS) play a key role in plant defense responses; and plant respiratory burst oxidase homolog (Rboh) genes family encodekey enzymatic subunit of NADPH oxidases which is a major component in ROS production.Recently, the Rboh genes have been identified from different model plants.It was reported that the gp91phox homologues NbRbohAand NbRbohBgenes playedan important role in N. benthamiana H2O2 accumulation andits resistance to Phytophthora infestans. Here we analyzed the roles of the N. benthamiana NbRbohB gene in resistance to Phytophthora spp, including compatible (Phytophthora capsici) and incompatiable (Phytophthora sojae) pathogens. These results help us make a better understanding of the mechanism of NADPH oxidases in plant resistance.Obvious oxidative burst was observed in N. benthamiana leaves while infected with both compatible and incompatiable pathogens, in which P. capsici caused more rapidly response than P. sojae. And the RT-PCR results showed that transcriptionallevel of NbRbohB gene was up-regulated during the infection stages of two Phytophthora pathogens, indicating that this gene is involved in oxdative burst. Using the virus-induced gene silencing approache, we silenced the N. benthamiana NbRbohB gene, the results indicated that when NbRbohB gene was silenced in N. benthamiana, the ROS accumulation and callose deposition were impaired, and the silenced plants showed increased susceptible to P. capsici. Pre-treatment of the N. benthamiana leaves with NADPH oxidase inhibitor also reduced the resistance to P. capsici. In contrast, silencing of the NbRbohB gene did not result in susceptibility to the incompatible pathogenP. sojae although ROS accumulation and callose deposition were reduced.These results indicate that NbRbohB is important for plant resistance to compatible Phytophthorapathogens by producing ROS.Otherwise, NbRbohB gene silencing showed no influence to the N. benthamiana none-host resistance to incompatiblePhytophthora pathogens.