Fig. 4

a Expression profiles of protease m1 zinc metalloprotease transcripts in five strains with different deltamethrin resistance levels. The results were shown as the mean ± S.E. Significant differences indicated by *(P < 0.05) and **(P < 0.01) were compared with the Lab-DS strain. b The relationship between protease m1 zinc metalloprotease transcriptional levels and deltamethrin resistance of Culex pipiens pallens. The Y-axis was the ratio of the gene expression in Lab-DR mosquitoes compared with that in Lab-DS mosquitoes, r = −0.97, P < 0.05