关键词: 油茶地蜂, 基因组, 比较基因组, 系统发育, 寡糖代谢

Abstract:  【Aim】 Andrena camellia is one of the most critical pollinators of Camellia oleifera. The aim of this study is to construct a genome-wide map of A. camellia compared with the genomes of other honey bee species of the Apidae, so as to investigate the evolutionary proximity of A. camellia to other honey bee species of the Apidae. 【Methods】 Illumina and PacBio sequencing technologies and high-throughput chromosome conformation capture (Hi-C) technology were employed to sequence the genomes of wild female adults of A. camellia collected from the C. oleifera plantation in Yichun, Jiangxi Province. Genome assembly and annotation were performed using Hifiasm and BLASTP software, and the evolutionary relationships between A. camellia and 15 other species of the Apidae were analyzed by clustering via MEGA software based on protein homology sequences. Based on the single-copy gene families shared by 16 insect species, the divergence time of each species was accurately estimated using the MCMCtree programme in the PAML software package. Orthologous gene Ks density distributions and gene family positive selection analyses of five species including A. camellia were performed with KaKs_Calculator software.【Results】Sequencing results showed that the genome of A. camellia was 265.44 Mb in length and contained 12 pairs of chromosomes, and the chromosome was 265.10 Mb in length. Cluster analysis indicated that A. camellia formed a group with Dufourea novaeangliae, Megalopta genalis and Nomia melanderi of Halictidae and Colletes gigas of Colletidae. The lowest Ks peaks between the orthologous gene pairs of A. camellia and C. gigas also proved that A. camellia was more closely related to C. gigas, which is the dominant pollinating insect for C. oleifera pollination. Division between A. camellia, members of Halictidae, and C. gigas occurred about 97.9 (87.1-111.2) million years ago. In the genome of A. camellia, a number of genes under positive selection were identified that might be associated with its characteristic black body colour and fatty acid metabolism pathways. Some extended gene families in the genome of A. camellia were significantly enriched in the galactose metabolism pathway (ko00052) (enrichment factor=0.0148). 【Conclusion】 A high-quality chromosome-level genome map of A. camellia was successfully constructed and served as a reference geneome. The ability of A. camellia to metabolize toxic oligosaccharides may be closely related to the expanding gene family of A. camellia. These findings provide new insights into solving the problem of poisoning of honey bees while foraging nectar and pollen from C. oleifera.

Key words: Andrena camellia, genome, comparative genomes, phylogeny, oligosaccharide metabolism