Propylea japonica (Coleoptera: Coccinellidae) is a natural enemy insect with a wide range of predation in Chinese mainland and is commonly used in pest management.  However, its genetic pattern (i.e., genetic variation, genetic structure, and historical population dynamics) is still unclear, impeding the development of biological control of insect pests.  Population genetic research has the potential to optimize strategies at different stages of the biological control processes.  This study used 23 nuclear microsatellite sites and mitochondrial COI genes to investigate the population genetics of Propylea japonica based on 462 specimens collected from 30 sampling sites in China.  The microsatellite dataset showed a moderate level of genetic diversity, but the mitochondrial genes showed a high level of genetic diversity.  Populations from the Yellow River basin were more genetically diverse than those in the Yangtze River basin.  Propylea japonica has not yet formed a significant genealogical structure in China, but there was a population structure signal to some extent, which may be caused by frequent gene flow between populations.  The species has experienced population expansion after a bottleneck, potentially thanks to the tri-trophic plant–insect–natural enemy relationship.  Knowledge of population genetics is of importance in using predators to control pests.  Our study complements existing knowledge of an important natural predator in agroecosystems through estimating its genetic diversity and population differentiation and speculating about historical dynamics.

The growth and development of skeletal muscle also determine the meat production of yak, ultimately affecting the economic benefits.  Hence, improving growth performance is a top priority in the yak industry.  Skeletal muscle development is a complex process involving the regulation of several genes, including microRNAs (miRNAs).  However, the transcription of miRNAs in yak skeletal muscle during prenatal to postnatal stages is unknown.  We used small RNA sequencing (small RNA-Seq) to determine the global miRNAs of longissimus dorsi muscle from yak (the samples were collected from three fetuses and three adults).  Totally 264 differently expressed miRNAs (|log₂(fold change)|>1 and P-value≤0.05) were detected between the two groups.  Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that differently expressed miRNAs-targeted genes participated in pathways associated with muscle development, such as MAPK, PI3K-Akt, and Hippo signaling pathways, etc.  MiR-652, which was up-regulated in the fetal group, was transfected into C2C12 myoblasts to examine its role.  miR-652 promoted (P≤0.05) proliferation and differentiation, but inhibited (P≤0.001) apoptosis at early period.  Furthermore, miR-652 reduced (P≤0.001) the proportion of C2C12 myoblasts in the G1 phase while increasing (P≤0.01) the proportion of cells in the S and G2 phases.  Dual-luciferase reporter assays indicated that ISL1 served as a target of miR-652.  In general, these findings expand our understanding of yak skeletal muscle miRNAs, and suggested that miR-652 probably regulated myogenesis by regulating ISL1.