The Research On OsWOX11 Regulated By OsEIL1 Involving In The Emergence Of Rice Crown Roots

The root system is an important part of vascular plant for growth and development.The root system of monocotyledonous plants represented by rice is mainly composed of primary root,crown roots and lateral roots.The primary root of rice stop growing at the seedling stage,and the crown roots are mainly used for water and nutrient absorption and plant fixation in the subsequent growth and development stages.The crown roots of rice develop from the crown root primordiums formed by initial cell division and differentiation,breaking through the epidermis,and the formation of the crown root primordiums are regulated by many factors.As an important plant hormone,ethylene plays an important role in physiological processes such as cell division,tissue differentiation,seed germination,fruit ripening,and adversity stress.Plant-specific WOX family transcription factors play an important role in plant embryogenesis,vascular differentiation,and root tip meristem maintenance.Among them,OsWOX11 can regulate rice crown roots development.This study found that exogenous application of ethylene can increase the number of crown roots of different varieties of wild-type rice,while the treatment of ethylene signal inhibitor 1-MCP inhibited the development of rice crown roots;the mutation of key components of ethylene signaling OsEIN2 and OsEIL1 had significantly fewer crown roots than wild-type mutants,and blocked the promotion of ethylene on the number of crown roots;the emergence of osein2 and oseil1 crown root primordia was observed relatively late in the paraffin section of their stem base,and they appear to be insensitive to ethylene,indicating that ethylene promotes the occurrence of rice crown root primordia through its signaling pathway.The WOX family transcription factor OsWOX11 plays an important role in the development of rice crown roots.Knockout of OsWOX11 made the number of crown roots significantly lower than that of the wild type,and the emergence of crown root primordia was relatively late.Meanwhile knockout of OsWOX11 blocked the promotion of ethylene treatment.While overexpression of OsWOX11 increase the number of crown roots and the emergence of crown root primordia was advance.Ethylene treatment for 3h significantily promoted the expression of OsWOX11 in the wild type,but in osein2 and oseil1,the expression of OsWOX11 decreased and was not regulated by ethylene,while its expression in EIN2-OX and EIL1-OX increased significantly.Electrophoretic mobility shift assay(EMSA)proved that OsEIL1 can directly interact with the EBS(EIL1 binding site)element on the OsWOX11 promoter.Transient expression experiments in tobacco and rice protoplasts also proved that OsEIL1 can bind to OsWOX11 promoter and activate its expression.Genetic analysis showed that the crown roots development of WOX11-CRS/eil1 was severely defective,and the paraffin section at the base of the stem showed that the crown root primordiums were seriously late,and the phenotype was more similar with WOX11-CRS.The crown roots number of WOX11-CRS/EIL1-OX is also suppressed,and the emergence of crown root primordias is consistent with that of WOX11-CRS,indicating that OsEIL1 is located upstream to regulate the transcription of OsWOX11,thereby affecting the occurrence of rice crown root primordia.The soil resistance experienced by rice in the process of rooting gradually increases,so we use different concentrations of phytagel to simulate the gradually increasing soil resistance.The results showed that the number of crown roots of seedlings grown in 0.8% phytagel was significantly increased compared with that of seedlings at 0.2% concentration.The paraffin section at the base of the stem also showed that the high concentration of phytagel made rice crown root primordium emerge earlier.The q PCR result found that increasing phytagel concentration can promote the expression of OsWOX11.By measuring the ethylene content,it was found that as the concentration of phytagel increased,the ethylene release of rice seedlings would also increase.Therefore,we conclude that the increased soil resistance during the rooting process of rice seedlings promotes the production of ethylene,and ethylene activates the expression of the downstream gene OsWOX11 through the key component of its signaling pathway,OsEIL1,and promotes the early emergence of crown roots.