Molecular Mechanism Of Ethylene And Gibberellin In Regulating Rice Primary Root Growth

Rice is an important monocotyledonous crop worldwide,improving rice root structure is important for increasing rice yield and stress resistance.Primary root is initiates during embryogenesis and develops shorty after germination,playing a vital role in the early seeding growth and survival.However,the molecular mechanism of primary root development is poorly understood.In this study,we analyzed the transcriptome expression profiling of primary roots of rice seedlings in different growth and development stages,and found that ethylene and gibberellin play an important role in regulating the growth and development of primary roots.Observing root apical meristem size indicating that ethylene inhibits and gibberellin promotes cell proliferation in the root meristem.Moreover,exogenous addition of gibberellin released the inhibition of ethylene on primary root growth.Determination of reactive oxygen species(ROS)content in primary roots found that ethylene inhibited and gibberellin promoted the accumulation of ROS in primary roots.Analysis of transcriptome expression profiling showed that OsGA2ox3,which have been identified and characterized to function in gibberellin catabolic pathway,was down regulated in oseil1.Further by ChIP and EMSA experiments demonstrated that OsEILl directly binds to the OsGA2ox3 promoter to activate its expression,thereby reducing endogenous gibberellin contents.Thus,our study reveals a model for the interaction of ethylene and gibberellin to regulate primary root development in rice,namely,OsEIL1 transcriptionally regulates OsGA2ox3 to reduce the endogenous gibberellin contents,which affects the accumulation of ROS in the primary roots of rice seedlings,and finally causes the primary roots to stop growing.