Objectives: Our purpose is dissecting the working principle of Jasmonate(JA)signaling pathway in fiber earlier development.Methods: Ovule culture system was used to prove that a suitable concentration of JA could promote cotton fiberinitiation.A new cotton geneGhJAZ2(repressor in JA pathway)containing a highly conserved TIFY motif and a C-terminal Jas domain was cloned and transferred into YZ1(Gossypiumhirsutum).ThenY2H and BIFC were used to find the interacting proteins with GhJAZ2,molecular and geneticexperiments were performed to prove the function of GhJAZ2in JA pathway in detail.Results: Ovule culture experimentprovedthat the ovules exhibited increased initiation in medium supplemented with 0.001 μM JA.Gene expression analysis showed that GhJAZ2 was preferentially expressed in the root,hypocotyl,flower and ovule one day before anthesis.Overexpression of GhJAZ2 inhibited both lint and fuzz fiber initiation and reduced the fiber length.Yeast two-hybrid and BIFC assays showed that GhJAZ2 interacted with the R2R3-MYB transcription factorsGhMYB25-like and GhGL1,the bHLH transcription factorGhMYC2,the WD repeat protein GhWD40 and the unknown protein GhJI1.Among these transcription factors,previous studies showed that down-regulation of GhMYB25-like led to a fiberless phenotype in cotton seeds.Molecular and genetic evidence showed that the GhJAZ2 protein reduced fiber initiation in the overexpressing lines by interacting with GhMYB25-like and suppressing GhMYB25-like activity.Conclusions:GhJAZ2 is the key repressor in the JA pathway and inhibits lint and fuzz fiber initiation by repressing the transcriptional activation of GhMYB25-like.