Complete mitochondrial genome sequence of the eri-silkworm, Samia cynthia ricini (Lepidoptera: Saturniidae)

The Samia cynthia ricini (Lepidoptera: Saturniidae: Bombycoidea), which is a commercial silk-producing insect has presumably been originated in India and is distributed in India, China, and Japan. Recently, the eri-silkworm is year-roundly reared in Korea for a diverse purpose. In this report, we present the complete mitochondrial genome of the species and compared the sequence mainly to Bombycoidea. The 15,384-bp long S. c. ricini mitochondrial genome was amplified and sequenced from 26 short overlapping fragments using 3 long overlapping fragments as temperate (COI ~ ND4, ND5 ~ lrRNA, and lrRNA ~ COI). Primers, designed from several lepidopteran mitochondrial genomes for universal purpose for Lepidoptera successfully amplified for both long and short fragments. The genome is composed of 37 genes: 13 PCGs, two rRNA genes, and 22 tRNA genes, and one major non-coding region termed the A+T-rich region. Arrangement of the genome is identical to those of other lepidopteran mitochondrial genome, but this differs from the common arrangement found in a diverse insect order, by the movement of tRNA^Met to a position 5’-upstream of tRNA^Ile. Overall the genome contains slightly lower AT content in whole genome, PCGs, rRNAs, and tRNAs than any other species of Bombycoidea. Unlikely previous report on the start codon for COI gene in Lepidoptera S. c. ricini COI gene appears to start with typical ATT codon located between tRNA^Tyr and the beginning region of COI gene. The 22 tRNAs that are interspersed throughout the mitogenome ranged in length from 62 to 71 bp. All tRNAs but tRNA^Ser(AGN) were shown to be folded into the expected cloverleaf secondary structures.