Juvenile hormone (JH) contributes to the regulation of larval molting and metamorphosis in insects. Herein, we comprehensively identified 55 genes involved in JH biosynthesis, metabolism and signaling in the silkworm (Bombyx mori) as well as 35 in Drosophila melanogaster, 35 in Anopheles gambiae, 36 in Apis mellifera, 47 in Tribolium castaneum, and 44 in Danaus plexippus. Comparative analysis showed that each gene involved in the early steps of the mevalonate (MVA) pathway, in the neuropeptide regulation of JH biosynthesis, or in JH signaling is a single copy in B. mori and other surveyed insects, indicating that these JH-related pathways or steps are likely conserved in all surveyed insects. However, each gene participating in the isoprenoid branch of JH biosynthesis and JH metabolism, together with the FPPS genes for catalyzing the final step of the MVA pathway of JH biosynthesis, exhibited an obvious duplication in Lepidoptera, including B. mori and D. plexippus. Microarray and real-time RT-PCR analysis revealed that different copies of several JH-related genes presented expression changes that correlated with the dynamics of JH titer during larval growth and metamorphosis. Taken together, the findings suggest that duplication-derived copy variation of JH-related genes might be evolutionarily associated with the variation of JH types between Lepidoptera and other insect orders. In conclusion, our results provide useful clues for further functional analysis of JH-related genes in B. mori and other insects.

The MYF5 gene is first inducibly expressed in muscle cell during embryonic muscle development and plays an important role in regulating the differentiation of skeletal muscle precursors. In this study we used PCR-RFLP to investigate two pig (Sus scrofa) populations (n = 302) for two MYF5 gene polymorphisms, a previously unreported novel Met-Leu shift single nucleotide polymorphism (SNP) MYF5/Hsp92II located on exon 1 and the previously identified intron 1 MYF5/HinfI SNP. Haplotype and association analysis showed that haplotypes of the two SNPs were significantly associated with drip loss rate (DLR, p < 0.05), water holding capacity (WHC, p < 0.05), biceps femoris meat color value (MCV2, p < 0.05), biceps femoris marbling score (MM2, p < 0.01), longissimus dorsi intramuscular fat percentage (IMF, p < 0.01) and longissimus dorsi Water moisture content (WM, p < 0.01) in the population 2. However, further studies are needed to confirm these preliminary results.