Transcription activator-like effector nucleases (TALENs) are a powerful approach for targeted genome editing and have been proved to be effective in several organisms.In the present study,we reported that TALENs can induce somatic mutations in Nile tilapia,an important species for worldwide aquaculture,with reliably high efficiency.Six pairs of TALENs were constructed to target genes related to sex differentiation,including dmrt1,foxl2,cyp19a1a,gsdf,igf3 and nrob1b (dax1b),and all resulted in indel (insertion or deletion) mutations with maximum efficiencies of up to 81% at the targeted loci.Effects of dmrt1 and foxl2 mutation on gonadal differentiation were analyzed by histological and immunohistochemcal analyses.In Dmrt1 deficiency testes,phenotypes of significant testicular regression,including deformed efferent duct,degenerated spermatogonia or even a complete loss of germ cells,and proliferated steroidogenic cells,were observed.In addition,disruption of Dmrt1 in XY fish resulted in increased aromatase gene (cyp19a1a) expression,serum estradiol-17.and 11-ketotestosterone levels.On the contrary,deficiency of Foxl2 in XX fish exhibited varying degrees of oocyte degeneration,significantly decreased aromatase gene expression and serum estradiol-17 levels.Some Foxl2 deficiency fish even exhibited complete sex reversal with high expression level of 11 -hydroxylase (Cyp11b2).Furthermore,disruption of Cyp19a1a in XX fish led to partial sex reversal.Taken together,our data demonstrated that TALENs are an effective tool for targeted gene editing in tilapia genome.Foxl2 and Dmrt1 play antagonistic roles in sex differentiation in Nile tilapia via regulating aromatase gene expression and estrogen production.