The Function And Molecular Mechanism Of Mir535-3p And Mir444b.2 Against Sheath Blight In Rice

Rice sheath blight is one of the most serious diseases on rice,and has a serious impact on the yield and quality of rice.With the amount of nitrogen fertilizer used in agricultural production increased,the promotion of short-stalked,multi-tiller and high-yield varieties,and the change of cultivation mode has caused the constant accumulation of Rhizoctonia solani in the field,and the degree of damage is increasing day by day.Because the occurrence of sheath blight is greatly affected by field climate,and the R.solani has a wide host range and strong saprophytic properties,and can survive in nature in the form of sclerotia and cause plant disease at all stages,which brings huge challenges to control.In this study,we constructed the knockout and overexpression materials about Osa-miR535-3p and Osa-miR444b.2,and analyzed the function of Osa-miR535-3p and Osa-miR444b.2 against R.solani;constructed a transcriptome sequencing library,and found hormone signal transduction genes,transcription factors and other important genes were up or down regulated significantly,further explore the defense response mechanism of rice sheath blight.The results of this study are as follows:1.After infected by R.solani,compared with wild-type plants,the disease severity of plants of Osa-miR535-3p knockout increased,while the overexpression plants was significantly reduced,showed certain resistance to R.solani,and the agronomic traits of rice were also significantly affected:after Osa-miR535-3p was overexpressed,the morphology of rice panicles changed significantly,and the number of secondary branches decrease,the panicles length becomes shorter,the plant height decreases,the number of tillers increase,and the thousand-grain weight decreases;but after knocking out Osa-miR535-3p,the number of secondary branches of the plant increases significantly,the ear length increases,and the number of tillers decreases.thousand-grain weight increased.2.After infected by R.solani,compared with wild-type plants,the disease degree of the plants is reduced after Osa-miR444b.2 knocked out inXu3,while the overexpression plants is heavier than wild type inYSBRl.It showed that increased the susceptibility to sheath blight.Similarly,Osa-miR444b.2 also has an impact on agronomic traits of rice:after overexpression it,the plant showed that the panicle length decreased,the plant height decreased,the number of tillers decreased,and the number of secondary branches decreased,thousand-grain weight increased.3.After preliminary determination of the phenotypes of transgenic plants infected by R.solani,this study used the Osa-miR535-3p and Osa-miR444b.2 knockout materials in Xudao and Osa-miR444b.2 overexpression materials in YSBR1 for R.solani infection and library construction.Nine transcriptome sequencing libraries were constructed from the leaf sheaths of infected parts at 0 hpi,8 hpi,and 16 hpi after infected by R.solani.The results showed that many differentially expressed genes are related to ethylene signaling,auxin signaling,abscisic acid signaling and other plant hormone signaling pathways.For example,Os01g64790,Os05g41760,Os03g20780,Os04g55520 are related to ethylene signaling pathway,Os03g18600,Os01g72910,Os02g33820 are related to abscisic acid signaling pathway;Os11g37970,Os12g36860,Os07g03730,Os12g36850,Os11g37950 are related to plant-pathogen interaction,and the levels of expression increased at 8 hpi and 16 hpi.In addition,the analysis results also showed that the expression of some transcription factors such as F-box and Myb also changed significantly,Os01g43650,Os08g38990,Os11g02530,Os09g25070 and other WRKY genes also up-regulated or down-regulated.indicating that these transcription factors also participate in the process of rice defense against sheath blight.Osa-miR535-3p and Osa-miR444b.2 participate in the process of rice response to R.solani infection and affect the agronomic traits of rice.The analysis found that some genes are involved in the process of rice sheath blight infection,such as auxin signal,ethylene signal,abscisic acid signal and other plant hormone signaling pathway,and transcription factors such as WRKY and F-box.These are provided support for further revealing the molecular mechanism of rice sheath blight resistance,and it also great significance for accelerating the breeding of rice sheath blight resistance varieties and improving the yield and quality of rice.