Ethylene and auxin are two key hormones for the somatic embryogenesis.However, the underlying molecular mechanisms that integrate these two hormones are poorly understood.Herein, the results of transcriptional profiling and expression analysis of ethylene biosynthetic genes indicate down-regulation of ethylene biosynthesis and response during Arabidopsis somatic embryogenesis.And the rate of ethylene biosynthesis in embryonic calli is gradually decreased during the formation of somatic embryos (SE).Treatment with the metabolic precursor of ethylene, 1-aminocyclopropane-l-carboxylic acid (ACC), inhibits the induction of SE.Similar phenotype can be shown in mutation at CONSTITUTIVE TRIPLE RESPONSE1 (CTR1), which causes a constitutive triple response of ethylene signaling.We also investigate the mechanisms of antagonistic ethylene effects on somatic embryogenesis.The effects of exogenous ACC or excessive ethylene signaling in tissues of ctrl mutants are mediated by disturbance of optimal auxin gradients through interference with auxin biosynthesis and polar auxin transport.Our results give a new sight on the function of ethylene on SE induction, and mutual regulation between ethylene and auxin during somatic embryogenesis in Arabidopsis