Study On Promotion Of Ethylene In Rice Crown Root Initiation

Ethylene,one of the phytohormones,has been revealed to perform key regulation in plant growth and development including seed germination,root development,flowering,fruit mature,senescence of leaf and flower,programmed cell death and stress toleration.Root is a vegetative organ,functioning in plant fixation,water and nutrition absorption.The root system of dicotyledons is composed of primary root and lateral root,while monocotyledons such as rice contains the primary root and crown root.During the early development of rice seeding,the primary root will gradually cease elongation,and then die.Simultaneously,the generation of crown root is enhanced to perform root function,indicating that the crown root plays an important role in plant growth and development.Crown root development is affected by various plant hormones,but the regulation of ethylene in this process is unclear.Increasing studies have shown that the development of rice crown root is from the formation of initial cells.Through cell differentiation,the initial cells of epidermis and endothelium are first generated,then via cell division,epidermis and endothelium are formed,subsequently the formation of basic tissues and crown root primordia.Finally,crown root primordia grow to form crown roots.WOX family genes can regulate plant growth and development in different species,for instance,OsWOX11 could regulate crown root development.In this experiment,we treament rice seedlings with different concentration of ethylene,found that ethylene can promote crown root initiation,and the number of root with ethylene concentration increases,the length of crown roots decreases,wild type rice seedling crown root primordium development also with ethylene concentration increases,these experiments can show that ethylene make rice root number increased through promoting rice root primordia;the number of rice root in oseil1 and osein2 was significantly reduced compared with its wild type,and the crown roots did not increase significantly after ethylene treatment,show that the ethylene insensitive phenotype,the crown root primordium development significantly worse than wild type.EIL1-OX and EIN2-OX number of crown root under normal conditions will be significantly more than the wild type,this experiment results show that ethylene promote the initiation of crown root is implemented through the its signal pathway.Previous reports have shown that OsWOX11 can regulate the initiation of rice crown root primordium and crown root elongation.So,does ethylene regulate the formation of rice crown root primordium through OsWOX11,or does it regulate rice crown root primordium through OsEIL1? To demonstrate this inference,we used In situ hybridization to demonstrate that OsEIL1 and OsWOX11 are expressed in crown root primordium.And only in the wild type ethylene induced OsWOX11 expression.OsWOX11 expression was decreased in oseil1 and osein2 materials but increased in EIL1-OX and EIN2-OX materials.Chromatin immunoprecipitation(ChIP)experiments also demonstrated that OsEIL1 interacts directly with OsWOX11 promoters at specific locations.The oswox11 material also showed that the number of crown roots was less than that of the wild type,the development of crown root primordia was worse than that of the wild type,and the crown roots showed a phenotype that was not promoted by ethylene.Ethylene regulates the function of OsWOX11 throughits signal pathway component OsEIL1.Genetic analysis also showed that the crown roots phenotype of oseil1 oswox11 was similar to oswox11.These results indicate that OsEIL1 regulates the expression of OsWOX11 at the transcription level,thereby affecting the development of crown root initiation.