Sequential loss of genetic variation in flea beetle Agasicles hygrophila (Coleoptera: Chrysomelidae) following introduction into China

Identification and Evaluation of Reference Genes for Quantitative PCR Normalization in Alligator Weed Flea Beetle (Coleoptera: Chrysomelidae)

Stably expressed reference genes are critical internal standards for the quantification of gene transcription levels using quantitative real-time PCR. Housekeeping genes are commonly used as reference genes but their expressions were variable depending on experimental conditions in many insect species studied. Here we report the identification and evaluation of 10 housekeeping genes in alligator weed flea beetle, Agasicles hygrophila Selman & Vogt (Coleoptera: Chrysomelidae), a biocontrol agent of alligator weed. The 10 housekeeping genes are: beta-actin (Actin), ribosomal protein L13A (PRL13a), succinate dehydrogenase complex subunit A (SDHA), ribosomal protein S20 (RPS20), ribosomal protein S13 (RPS13), glyceraldehyde phosphate dehydrogenase (GAPDH), TATA-box-binding protein (TBP), ribosomal protein L32 (RPL32), tubulin alpha-1 chain (TUBULIN), and elongation factor-1 alpha (ELF). Five programs, geNorm, NormFinder, BestKeeper, ΔCt method, and RefFinder, were used to evaluate the expression stability of the 10 genes among various A. hygrophila body parts and with different nutrient types (starvation, diet types). The expression stability analysis showed that RPS32 and RPL13a were reliable reference genes for the study of gene transcription in different body parts; Actin and RPL13a were optimal reference genes for different nutrient types. The selections of reference genes were validated using a CarE gene (GeneBank No: KX353552). The results of this study provide useful bases for studies of gene expression in various aspects relating to A. hygrophila.

The complete mitochondrial genome of the flea beetle Agasicles hygrophila

To provide molecular markers for population genetic analysis of the flea beetle Agasicles hygrophila, we determined its mitochondrial genome (mitogenome) for the first time. The mitogenome of A. hygrophila was 15 917 bp in length with an AT content of 75.15%. It had the typical set of 13 protein-coding genes (PCGs), 22 tRNA genes, two rRNA genes, and an AT-rich control region. Compared with the ancestral mitogenome of insects, no gene rearrangement occurred in A. hygrophila. Incomplete stop codons were present in PCGs of A. hygrophila. All tRNA genes except for trnS(AGN) could form the typical clover-leaf secondary structures. The phylogenetic analysis indicated that A. hygrophila was close to other species belonging to the same family of Chrysomelidae.