Insect immune responses are precisely regulated to maintain immune balance.Although in locust immune responses and regulatory mechanisms have been well studied,to the best of our knowledge,there is no report on immune negative regulatory mechanisms.In this study,a full-length eDNA encoding Fas-associated factor 1 (LmFAF1) was cloned based on EST analysis of a transcriptome for Locusta migratoria manilensis (Meyen).Gene expression analysis,as determined by real-time quantitative PCR,showed that the presence of LmFAF1 transcripts during the whole development processes and in all tissues tested,but varied significantly after challenge with Gramnegative bacteria E.coli (DH5a),the diptericin gene (LmDpt) was rapidly induced,whereas the expression of LmFAF1 was reduced markedly.It is consistent with the observation that LmDpt was highly expressed when LmFAF1 is suppressed by RNA interference.In conclusion,these findings suggested that LmFAF1 may play a negative regulatory role in Imd immune signaling pathway of locust.