关键词: 棉铃虫, 草地贪夜蛾, 原肌球蛋白, RNAi, 存活率, 体重, 取食量

Abstract: 【Aim】 This study aims to conduct tissue expression profile and RNAi effect analyses of tropomyosin gene of Helicoverpa armigera HaTm-1,  previously identified through transcriptome screening, so as to explore the feasibility and theoretical basis of HaTm-1 as a broad-spectrum RNA biopesticide target for lepidopteran pests. 【Methods】 The cDNA sequence of HaTm-1 of H. armigerawas cloned using PCR and analyzed through bioinformatics. RT-qPCR was used to detect the expression levels of HaTm-1 in different tissues of the 4th instar larvae, including cuticle, fat body, midgut, brain, testis and Malpighian tubules, as well as in the cuticle of the 2nd-5th instar larvae of H. armigera. RNAi of HaTm-1 was performed by spraying dsHaTm-1 on the 1st instar larvae of H. armigera and Spodoptera frugiperda. The expression levels ofHaTm-1 of H. armigera and HaTm-1 of S. frugiperda, and the larval weight and larval survival rate of these species were subsequently measured. dsHaTm-1 was injected into the 4th instar larvae of H. armigera, and the larval weight, pupal weight, relative growth rate, relative metabolic rate and food intake were detected. 【Results】 The full-length cDNA of HaTm-1 of H. armigera was 855 bp (GenBank accession no.: XP021201113.1). HaTm-1 had the amino acid sequence identity of over 90% with homologous proteins in multiple species. Tm-1s of H. armigera and S. frugiperda converged on the same clade, suggesting a close relationship between them. HaTm-1 was specifically and highly expressed in the cuticle of the 4th instar larvae of H. armigera and was also expressed in the cuticle at different larval instars, with peak expression occurring in the cuticle of the 5th instar larva. There was a decrease in the expression level of HaTm-1 by 55.73% and 50.85% at 12 and 24 h, respectively, a significantly reduced larval survival rate by 43.33% at 168 h， and decrease in the larval weight by 17.67%, 14.65% and 18.90% at 72, 120 and 168 h, respectively, after spraying dsHaTm-1 to the 1st instar larvae of H. armigera, as compared with those in the dsEGFP control group. The expression level of SfTm-1 decreased by 44.72% and 39.65% at 12 and 24 h, respectively, after spraying dsHaTm-1 on the 1st instar larvae of S. frugiperda as compared with those of the dsEGFP control group. The larval survival rate was observed to be 60% at 144 h after spraying dsHaTm-1 on the 1st instar larvae of S. frugiperda. The larval weight decreased by 13.00% and 28.11% at 72 and 120 h， respectively, after spraying dsHaTm-1 on the 1st instar larvae of S. frugiperda as compared with those of the dsEGFP control group. The expression level of HaTm-1 was significantly reduced by 55.66% at 24 h, the larval weight was decreased by 50.34% and 54.91%, respectively, at 72 and 120 h， the pupal weight was reduced by 13.14%, the relative growth rate was decreased by 14.00%, the relative metabolic rate was decreased by 15.66% and the food intake was decreased by 14.50%, after injecting the 4th instar larvae of H. armigera with dsHaTm-1 as compared with those of the dsEGFP control group. These alterations in feeding and digestion processes ultimately resulted in larval death. 【Conclusion】 The interference of HaTm-1 expression is vital to the feeding and digestion processes in H. armigera. This study underscores the potential of tropomyosin as a broad-spectrum target for RNA biopesticides, offering valuable insights for its practical application.

Key words: Helicoverpa armigera, Spodoptera frugiperda; tropomyosin, RNAi, survival rate, body weight, food intake