| microRNAs (miRNAs) are a class of endogenous noncoding RNAs about23nucleotides in length that serve important functions in eukaryotes by posttranscriptional gene regulation. They are one of the main aspects of epigenetics field. The honey bee (Apis mellifera) is a key model for highly social species, and its complex social behavior can be interpreted theoretically as changes in gene regulation, in which miRNAs are thought to be involved. Caste differentiation in the female honey bee is one of the most intriguing epigenetics phenomena. This developmental switch depends not on the genomic differences between the queens and workers but on the differential expression of entire suites of the genes involved in the larval fate between the queens and workers.Taking advantage of the SOLiDTM sequencing system, we identified the repertoire of miRNAs in honey bee, as well as candidate functional miRNAs/mRNAs during caste differentiation of female honey bee. The contents and major results are listed as follows.1. Identification of the repertoire of miRNAs in the honey bee. A total of267novel honey bee miRNAs were identified from a mixed small RNA library constructed by different developmental stages of queen, drone and worker by sequencing. Cross-species analyses showed81novel miRNAs have homologues in other insects, suggesting that they have similar functions. The results of this study enriched the types and numbers of honey bee miRNAs, which provide a basis for studies of miRNAs involved in development, differentiation, disease and other biological phenomena in honey bee, and for miRNAs identification and function studies in other insects or animals.2. Comparision of mRNAs between full-sister queen-(QL) and worker-destined larvae (WL). The mRNA libraries of fourth-instar queen larvae (QL4), fourth-instar worker larvae (WL4), fifth-instar queen larvae (QL5) and fifth-instar worker larvae (WL5) were constructed. As a result,7,952,7,993,7,971, and8,023genes were assembled respectively after sequencing. More than4,500differentially expressed genes (DEGs) between the castes were obtained. Over70%of the DEGs in each instar were more highly expressed in QL than in WL, possibly suggesting that the transcriptional activity of QL genes were higher than WL genes’ during differentiation. The same gene set is active (but differentially expressed) in both castes, which in turn results in dimorphic females. These results could contribute to an in-depth study of the candidate genes during honey bee caste differentiation, and improve our current understanding of the polyphenisms in insects.3. Comparison of miRNAs between full-sister queen-(QL) and worker-destined larvae (WL). Small RNA libraries of QL4, WL4, QL5and WL5were constructed. As a result,92、96、91and95known honey bee miRNAs, as well as35、61、74and111novel miRNAs were obtained respectively. The expression of ame-mir-14ame-mir-750、ame-mir-279c、ame-bantam were in top5in all libraries, suggesting that these miRNAs might be essential during L4and L5development for female honey bee. Twenty-eight known honey bee miRNAs were specifically or preferentially expressed,23of them were not found in other species yet, alternatively, these miRNAs might specifically expressed in honeybee. We also predicted targets for known honey bee miRNAs. Results suggested that ame-mir-14might play a role in immune system, especially for WL; The ame-mir-2796might regulate worker labor division by involving in neuronal development and differentiation, through its host gene, PLC-epsilon gene. The ame-mir-34and ame-mir-317might play a role in brain development in honey bee. Results also provide a basis for studies of miRNAs involved in development or differentiation in honey bee larva even whole honey bee life, and supply a cue for studies of miRNA effects on polyphenisms in other insects or animals. |
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