Characterization Of Two Component System MoSLN1 And MoSKN7 In Development And Pathogenicity Of Magnaporthe Oryzae

The ascomycete Magnaporthe oryzae, the causal agent of rice blast disease, is the most destructive pathogen of cultivated rice worldwide. Each year rice blast causes losses of between 10 and 30% of the rice harvest. Recently, control measures like the use of resistant cultivars and application of fungicides have not allowed complete eradication of the disease. However, the availability of the genome sequences of both rice and the fungal pathogen have not only accelerated the discovery of pathogenesis related genes but also help research to find novel targets of chemical control and provide new sight and good idea for designing comprehensive management of Magnaporthe oryzae.Two-component systems (TCSs) regulate a wide variety of cellular processes, such as cell motility, cell cycle control, development, antibiotic resistance, and microbial and fungal pathogenesis, as well as respond to hormonal stimuli and environmental stress, in bacteria, fungi, slime molds, and plants. The basic two-component system involves a sensor kinase, or HPK, as well as an RR; most eukaryotic TCSs include three components:a hybrid-type histidine kinase, a His-containing phosphotransfer protein, and a response regulator.In Saccharomyces cerevisiae, a Slnl-Ypdl-Sskl osmolarity-response pathway is essential to controls adaptive responses to high osmolarity. This phosphorelay system is initiated by the autophosphorylation of Slnl, then to a intermediary protein Ypdl and finally to response regulator Sskl. Phosphorylated Sskl is incapable of activating the Ssk2 and Ssk22 MAPKKKs and thus inhibits signaling via the HOG1 MAPK cascade. Another RR protein, Skn7, is involed in oxidative stress response in yeast.We characterized a two component system histidine kinase MoSlnl, a homolog of Slnlp in Saccharomyces cerevisiae. MoSlnl is a protein encodes 1202 amino acid with a signal peptide, a highly conserved histidine kinase domain and a histidine kinase-like ATPases. Disruption of MoSLNl resulted in hypersensitivity to various stresses, reduced sensitivity to cell wall perturbing agent Calcofluor white, and loss of pathogenicity, mainly due to a penetration defect. Additionally, we showed that MoSLNl is involved in oxidative signaling through modulation of intra-and extracellular peroxidase activities. These results indicate that MoSLNl functions as a pathogenicity factor that plays a role in responses to osmotic stress, the cell wall integrity, and the activity of peroxidases. A RR gene in Magnaporthe oryzae, MoSKN7, which encodes a 672 amino acid protein, possesses a HSF domain which is a heat shock factor and a REC domain contains a phosphoacceptor site that is phosphorylated by histidine kinase homologues. Targeted gene deletion of MoSKN7 resulted in the change of the mutant colony melenization and sensitivity to H2O2. These results suggest that MoSLN1 is involed in pathogenicity independent on MoSKN7 in Magnaporthe oryzae, although MoSKN7 is the downstream regulator of MoSLN1.