Study On The Regulation Of Rice Karrikins Signaling Pathway On Interaction Between Rice And Magnaporthe Oryzae

Plants can specifically recognize and distinguish between pathogenic and beneficial bacteria,thus activating the correct response in time.In recent years,the molecular mechanism of plant recognition of immune and symbiotic signals has been revealed,but little is known about how plants distinguish immune and symbiotic signals.It has been shown that the Karrikins(KAR_S)signaling pathway is necessary for the colonization of arbuscular mycorrhizal fungi in rice.However,whether this pathway is involved the interaction between pathogenic fungi(Magnaporthe oryzae)and rice is still lacking.To explore whether Karrikins signaling pathway is involved in both immune response and symbiotic response in plants,we investigated the infection of M.oryzae in of Karrikins signaling mutants in rice.Rice Karrikins signaling mutants d14l(KARs receptor),d14(SLs receptor),Ossmax1(Karrikins signaling repressor),Ossmax1 d14l,Ossmax1 d14 mutants and OsSMAX1m-OE transgenic plants were used as materials.The results showed that Ossmax1,Ossmax1 d14,and Ossmax1 d14l had less number of lesions than those of wild type,suggesting that OsSMAX1 loss of function improved the resistance of rice blast.Accordingly,the expression of PR1a induced by M.oryzae was significantly increased in Ossmax1,Ossmax1 d14 and Ossmax1 d14l.In addition,Ossmax1 mutant inhibited the expansion of the mycelia infected by M.oryzae by observing the rice leaf sheath infection process of a GFP-expressed M.oryzae(Zhong10).DAB staining showed that the level of reactive oxygen species increased in Ossmax1 mutants,suggesting that increased of production of reactive oxygen species(ROS)or deceased scavenging of ROS in Ossmax1 may prevent the infection of M.oryzae.The results of RNA-seq indicated that the high expression of disease resistance related genes in Ossmax1 mutant might be responsible for disease resistance in Ossmax1 rice.These results suggested that the Karrikins signaling pathway regulates the interaction between rice and M.oryzae.OsSMAX1 negatively regulates the expression of key genes DMI3 and IPD3 in the common symbiosis signaling pathway(CSSP).To further studied the mechanism of OsSMAX1 affecting susceptibility of rice to M.oryzae.It showed that the castor,dmi3 and ipd3 mutants showed similar infection phenotypes as WT,indicating that CSSP may not be involved in the interaction between rice and M.oryzae.The expression of OsERF67 and OsERF68,homologous genes of Mt ERF19 in rice,were increased in the Karrikin signaling mutant.We ound that the loss of function mutant of OsERF67 showed disease resistance to M.oryzae.It is possible that Karrikins signaling pathway may promote the infection process of M.oryzae by inhibiting the plant immune response through OsERF67.In summary,we found that OsSMAX1,an repressor of Karrikins signaling pathway,may be a key gene that regulates both symbiosis and immune response in rice.The Karrikins signaling pathway may regulate rice blast resistance by modulating expression of OsSMAX1downstream genes.This study revealed that the Karrikins signaling pathway may mediate the cross-talk between plant symbiosis and immune response in rice.To understand the molecular mechanism of Karrikkins signaling pathway involved in the interaction between rice with symbolistic or with pathogenic fungi would provide insight for the development of rice disease-resistant varieties.