Effects of Bt induced immune sensitization on cotton bollworm(Helicoverpa armigera)in relation to the cecropin(HacD)expression
Antimicrobial peptides constitute a crucial aspect of insect humoral immunity,playing a vital role in combating exogenous pathogenic microorganisms.Understanding the spatial and temporal dynamics of antimicrobial peptide gene transcription,such as HacD in the cotton bollworm induced by Bacillus thuringiensis(Bt),is pivotal to elucidating the correlation between insect humoral immunity and the development of resistance to Bt in cotton bollworm.In this study,the sequence of HacD cDNA was obtained,its protein was translated,the transcriptional pattern of the HacD gene in cotton bollworm under Bt induction was studied by RT-qPCR.The results showed that the HacD cDNA of cotton bollworm was 189 bp in length,with a GC content of 48.15％,resulting in a peptide chain consisting of 63 amino acids.The relative transcript levels of HacD were significantly up-regulated in cotton bollworm larvae after Bt induction,with the highest level in fat body,followed by the hemolymph.After short-term Bt induction,the relative transcript levels of HacD genes were continuously up-regulated in both fat body and hemolymph,reached the highest level when induced for 24 h and 18 h,respectively,and then gradually declining.Furthermore,continuous induction to larvae led to a maintaining up-regulation of transcriptional levels of HacD genes across various developmental stages,including neonate larvae,the 5th-instar larvae,pupae,and adults in F0 generation.The transcript levels of HacD genes in Fi generation individuals came from F0 generation displayed a down-regulated trend compared to those in F0 generation,but all were higher than those in the control group.In summary,Bt can cause up-regulation of HacD gene transcription level in cotton boll worm.
Helicoverpa armigeraBacillus thuringiensisimmune sensitizationresistancececropinfat body
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