Mechanism Of Phytochrome B In Regulating Rice Sheath Blight Resistance

Rice sheath blight is a serious crop disease caused by Rhizoctonia solani AG1-IA.Due to the complex classification,wide host range and rapid spread of its pathogenic bacteria,rice sheath blight is difficult to control and can cause up to 45% yield loss.The use of fungicides is still the main strategy to control sheath blight at present,but the excessive use of chemicals can cause destructive effects on the environment,and the most ideal varieties of sheath blight have not yet been found,so screening and breeding resistant varieties has become a major challenges in disease control.This paper takes Phytochrome B in the rice phytochrome family as the research object,and provides new ideas for the study of its regulation mechanism of rice sheath blight resistance through experimental methods such as pathology and molecular biology.The following are the research results:1.Rice Phytochrome B negatively regulates rice sheath blightThrough the Ds insertion mutant population,it was found that osphyB is insensitive to rice sheath blight.Therefore,the rice phytochrome Phytochrome B was selected as the research object to preliminarily explore the mechanism of its regulation of sheath blight.Firstly,q RT-PCR test was carried out in 4 different time periods after wild-type inoculation of R.sheath blight AG1-IA to detect the expression of OsPhyB.The results showed that the expression of OsPhyB was affected by rice sheath blight.In order to further verify the disease resistance function of OsPhyB,in vitro and living leaf sheathing experiments were carried out.The results showed that the osphyB mutant was more resistant to disease than the wild type,and OsPhyB OX was more susceptible than the wild type.In conclusion,OsPhyB negatively regulated rice sheath blight.After shading and light-treated wild-type rice seedlings were inoculated with live leaf sheaths,it was found that the shading seedlings had less disease,and the amount of OsPhyB protein entering the nucleus under shading conditions was reduced,which was equivalent to simulating the osphyB mutant form,inhibiting the function of OsPhyB,thereby improving the Resistance of rice to sheath blight.2.Functional identification of the phytochrome-interacting factor OsPILsTo preliminarily explore the mechanism of OsPhyB regulating rice sheath blight resistance,firstly,the downstream interacting proteins of OsPhyB,OsPIL14 and OsPIL15,were screened.Assuming that OsPIL protein accumulation is involved in regulating resistance after osphyB mutation in rice as reported in Arabidopsis thaliana,OsPIL over expressing plants should be more disease resistant compared to wild type.However,the inoculation test showed that OsPIL14,15 OX plants were susceptible to disease compared with wild-type controls,and OsPIL15 RD plants were disease resistant compared to wild-type controls.No results consistent with the hypothesis were obtained,suggesting that the resistance of osphyB mutants to rice sheath blight cannot be explained by PIL function.3.OsPhyB-OsVOZ2 interaction in regulating rice sheath blight resistanceAccording to literature review,VOZ protein is one of the largest transcription factor families in plants and plays a key role in plant immunity.In the model plant Arabidopsis thaliana,VOZ specifically functions downstream of PhyB in the flowering pathway,PhyB interacts with VOZ1/2,and the VOZ protein in the nucleus is phytochrome-dependent under far-red and dark conditions way to degrade.In order to further explore the disease resistance mechanism of osphyB,the interaction between PhyB and VOZ2 protein in rice was first confirmed by Y2 H,Bi FC and Co-IP.We speculate that a similar degradation mechanism exists in rice as in Arabidopsis,and the osvoz2 T-DNA mutant should be more susceptible than wild-type.Further phenotypic verification showed that the osvoz2 T-DNA mutant was susceptible to the disease compared to the wild-type control,and the results were consistent with the guess.Therefore,it can be speculated that OsPhyB-OsVOZ2 forms an interaction network to regulate rice sheath blight resistance.In this paper,experimental methods such as pathology and molecular biology were used to clarify that the rice Phytochrome B negatively regulates rice sheath blight.It is further speculated that OsPhyB-OsVOZ2 may form an interaction network to regulate rice sheath blight,which provides a new idea for the molecular mechanism of resistance of osphyB mutants.