Comparison of the mitochondrial genomes of three geographical strains of Apis laboriosa indicates high genetic diversity in the black giant honeybee (Hymenoptera: Apidae).

Apis laboriosa is the largest honeybee that lives mainly on cliff faces, with strong migratory ability. In this study, we firstly sequenced and assembled two complete mitochondrial genomes of A. laboriosa isolated from two distant locations in China (Chongqing and Shangri-La regions). Combined with the published mitochondrial genome of A. laboriosa from Nepal, comparative genomic analyses were conducted to gain insight into the genetic diversity of giant honeybees from different geographical distributions. The mitochondrial genomes of A. laboriosa from Chongqing and Shangri-La regions were 15,579 and 15,683 bp in length, respectively, both larger than that from Nepal with the length of 15,510 bp. Three mitochondrial genomes all harbor 37 common genes and present the same AT bias and the frequency of codon usage. However, the fragments including COX1, SSUrRNA, LSUrRNA, and the AT-rich region of the mitochondrial genome from Shangri-La region demonstrate distinctive insertions and deletions compared to those from Chongqing and Nepal regions. Phylogenetic trees of mitochondrial genomes show that A. laboriosa from Chongqing is most closely related to that from Nepal, rather than to Shangri-La. Genetic distance between Shangri-La and Chongqing or Nepal was even larger than that between the various subspecies of Apis mellifera. Overall, these results unmark that A. laboriosa in different geographical distributions can exhibit high genetic diversity at the mitochondrial genomic level, and therein, A. laboriosa from Shangri-La may be the subspecies. All these studies will contribute to our understanding of the geographical distribution and genetic differentiation of black giant honeybee in Asian region.

Genome and Evolutionary Analysis of Nosema ceranae: A Microsporidian Parasite of Honey Bees.

Microsporidia comprise a phylum of single cell, intracellular parasites and represent the earliest diverging branch in the fungal kingdom. The microsporidian parasite Nosema ceranae primarily infects honey bee gut epithelial cells, leading to impaired memory, suppressed host immune responses and colony collapse under certain circumstances. As the genome of N. ceranae is challenging to assembly due to very high genetic diversity and repetitive region, the genome was re-sequenced using long reads. We present a robust 8.8 Mbp genome assembly of 2,280 protein coding genes, including a high number of genes involved in transporting nutrients and energy, as well as drug resistance when compared with sister species Nosema apis. We also describe the loss of the critical protein Dicer in approximately half of the microsporidian species, giving new insights into the availability of RNA interference pathway in this group. Our results provided new insights into the pathogenesis of N. ceranae and a blueprint for treatment strategies that target this parasite without harming honey bees. The unique infectious apparatus polar filament and transportation pathway members can help to identify treatments to control this parasite.

[Pathogenicity and genetic divergence of two isolates of microsporidia Nosema bombycis].

Microsporidia Nosema bombycis is a fungal pathogen that causes epidemic pebrine disease in Bombyx mori. Two N. bombycis isolates were obtained from two areas in China and showed different pathogenicity after Spodoptera frugiperda Sf9 cell cultivation. The regions of rDNAs from different isolates were analyzed, suggesting no relationship between the genetic divergence and their geographic distributions. Further analysis showed that several copies of SSU rDNA units in N. bombycis were interrupted by a MITE-like transposon, indicating the complexity of genomic structure in Nosema bombycis.

[Advances of transposable element in genome of protozoa parasite].

Transposable elements are important factors to cause genetic variation and recombination, which are widely spread in eukaryotic organisms. Object to the increasing numbers of transposable elements in protozoa genome, this review focus on the types and genomic distributions of transposable elements in newly completed genome of protozoa parasite, mainly including Trypanosoma, Leishmania, microsporidia, Amoebozoa. The LINE and SINE elements are predominated in protozoa genome, followed by the DNA transposons and LTR retrotransposons. Several elements incline to insert in AT-rich region, suggesting the possible close relationship between the activity of transposable elements and AT content of genome. By the comparison of the divergence of transposable elements in microspordian genome, it was hypothesized that at least one loss event of transposable element had occurred during microsporidian genomic evolution. Finally, the prospects of trans-posable elements were discussed in the application of functional gene research of protozoa.

SilkPathDB: a comprehensive resource for the study of silkworm pathogens.

Silkworm pathogens have been heavily impeding the development of sericultural industry and play important roles in lepidopteran ecology, and some of which are used as biological insecticides. Rapid advances in studies on the omics of silkworm pathogens have produced a large amount of data, which need to be brought together centrally in a coherent and systematic manner. This will facilitate the reuse of these data for further analysis. We have collected genomic data for 86 silkworm pathogens from 4 taxa (fungi, microsporidia, bacteria and viruses) and from 4 lepidopteran hosts, and developed the open-access Silkworm Pathogen Database (SilkPathDB) to make this information readily available. The implementation of SilkPathDB involves integrating Drupal and GBrowse as a graphic interface for a Chado relational database which houses all of the datasets involved. The genomes have been assembled and annotated for comparative purposes and allow the search and analysis of homologous sequences, transposable elements, protein subcellular locations, including secreted proteins, and gene ontology. We believe that the SilkPathDB will aid researchers in the identification of silkworm parasites, understanding the mechanisms of silkworm infections, and the developmental ecology of silkworm parasites (gene expression) and their hosts. Database URL: http://silkpathdb.swu.edu.cn.