【目的】 鉴定小地老虎Agrotis ipsilon保幼激素酸甲基转移酶（Juvenile hormone acid O-methyltransferase）AiJHAMT2基因，解析其序列特征，并明确其生物学功能。【方法】 利用同源检索技术从小地老虎转录组中鉴定AiJHAMT2的cDNA序列，使用生物信息学软件分析其序列特征，通过RNA干扰技术沉默AiJHAMT2，分析小地老虎幼虫保幼激素滴度、存活率、体长、体重、化蛹率和羽化率的变化。【结果】 AiJHAMT2的开放阅读框为855 bp，其编码的蛋白质具有昆虫JHAMT的典型特征，包括S-腺苷甲硫氨酸结合域以及11个能够与底物发生互作的氨基酸残基。AiJHAMT2基因位于小地老虎12号染色体，在基因组上的长度为5 673 bp，包含4个外显子和3个内含子。系统进化分析结果表明AiJHAMT2与东方粘虫Mythimna separata MsJHAMT2进化关系最近。向小地老虎3龄幼虫注射靶向AiJHAMT2的双链RNA能够有效沉默该基因，注射后24和48 h时，AiJHAMT2表达水平与对照组相比分别显著下降了74.0%（P=0.026）和76.6%（P=0.008），而AiJHAMT1表达水平在注射后48 h时显著上升至对照组的2.21倍（P=0.009）。沉默AiJHAMT2后，幼虫保幼激素滴度显著下降了46.4%（P=0.020），幼虫存活率、体长、体重和化蛹率分别显著降低了28.1%（P<0.001）、31.7%（P=0.007）、36.3%（P=0.002）和35.2%（P<0.001），但沉默AiJHAMT2未对小地老虎羽化率产生显著影响（P=0.252）。【结论】 沉默AiJHAMT2显著降低小地老虎幼虫存活率并阻碍其生长和化蛹，表明该基因具有作为RNA干扰靶标用于小地老虎防治的潜力。

 [Aim]  To identify the AiJHAMT2 gene in Agrotis ipsilon, analyze its sequence characteristics and clarify of its biological functions. [Methods]  The cDNA sequence of AiJHAMT2 was identified from the A. ipsilon transcriptome using a homology search method. The sequence characteristics of AiJHAMT2 were analyzed using bioinformatic software. AiJHAMT2 was silenced with RNA interference technology and subsequent changes in juvenile hormone (JH) titer, larval survival rate, body length, body weight, and pupation, and emergence rates, were assessed. [Results]  AiJHAMT2 contained an open reading frame of 855 bp. The protein encoded by AiJHAMT2 possessed features typical of other insect JHAMTs, including a S-adenosyl methionine-binding motif and 11 conserved substrate-interacting residues. The AiJHAMT2 gene was localized on chromosome 12, and its genomic sequence spans 5 673 bp, comprising four exons and three introns. Phylogenetic analysis revealed that AiJHAMT2 is most closely related to Mythimna separata MsJHAMT2. Injection with double-stranded RNA (dsRNA) targeting AiJHAMT2 effectively silenced the gene in 3rd instar larvae. Expression of AiJHAMT2 significantly decreased by 74.0% (P=0.026) and 76.6% (P=0.008), respectively, 24 and 48 h post-injection compared to the control group, whereas expression of AiJHAMT1 significantly increased by 2.21-fold compared to the control group 48 h post-injection (P=0.009). Silencing AiJHAMT2 significant reduced the JH titer of larvae by 46.4% (P=0.020). This also significantly reduced larval survival rate, body length, body weight, and pupation rate by 28.1% (P<0.001), 31.7% (P=0.007), 36.3% (P=0.002), and 35.2% (P<0.001), respectively. However, silencing AiJHAMT2 had no significant effect on the emergence rate (P=0.252). [Conclusion]  Silencing AiJHAMT2 significantly reduced larval survival rate and impaired larval growth and pupation, demonstrating that this gene is a potential RNAi target for controlling A. ipsilon.