Recipe for a Busy Bee: MicroRNAs in Honey Bee Caste Determination

Abstract

Social caste determination in the honey bee is assumed to be determined by the dietary status of the young larvae and translated into physiological and epigenetic changes through nutrient-sensing pathways. We have employed Illumina/Solexa sequencing to examine the small RNA content in the bee larval food, and show that worker jelly is enriched in miRNA complexity and abundance relative to royal jelly. The miRNA levels in worker jelly were 7–215 fold higher than in royal jelly, and both jellies showed dynamic changes in miRNA content during the 4th to 6th day of larval development. Adding specific miRNAs to royal jelly elicited significant changes in queen larval mRNA expression and morphological characters of the emerging adult queen bee. We propose that miRNAs in the nurse bee secretions constitute an additional element in the regulatory control of caste determination in the honey bee.

Differential expression of miRNAs related to caste differentiation in the honey bee, Apis mellifera

“…We previously showed that miRNAs in jellies could influence the caste determination of worker and queen bee larvae (Guo et al 2013). Here, we have profiled the small RNAs of fourth to sixth day worker and queen larvae using deep sequencing and qRT-PCR to explore the mechanism of caste determination and found that 53 known miRNAs were expressed in the early and critical caste developmental stages of bees, a number of which were shown higher in either queen or worker larval bees than the others, respectively.…”

“…To analyze the miRNA expression levels at different developmental stages (day 4, day 5, day 6) in workers and queens, the ΔCT values for different developmental stages were calibrated against the respective CT value of the day 4 sample in queens. qPCR results are presented as the fold expression relative to the day 4 sample in queens as performed in other study (Guo et al 2013) unless otherwise stated.…”

“…After the third day of larval development, differences in nutritional or other environmental factors cause the development of workers and queen larvae to take distinct developmental paths (Dedej et al 1998;Evans and Wheeler 2001;Guo et al 2013;Kucharski et al 2008). Artificial queens rearing with worker larvae grafted from the fourth day or days later would develop significantly decreased number of ovarioles and basitarsal index (Dedej et al 1998) when compared to ones rearing from early stages, showing that the age around 3.5 days is committed to the development of honey bee as either worker or queen.…”

“…Zondag et al found that 28 % of known miRNAs could be expressed in the early embryo (24-30 h), and these miRNAs played roles in patterning segmentation (Zondag et al 2012). Shi et al and Guo et al demonstrated that miRNAs were present in bee jellies and these jelly miRNAs may play important functions in the caste development of bees (Guo et al 2013;Shi et al 2012). In addition, Shi et al compared the miRNA profiles between queen larvae and worker larvae at 4 days old (Apis mellifera ) and found that 37 miRNAs were differentially expressed between these two castes in this specific stage (Shi et al 2015).…”

Uptake and impact of natural diet-derived small RNA in invertebrates: Implications for ecology and agriculture

“…Similarly, bee-derived miRNAs may be transferred to larval honey bees via inoculation of royal jelly with miRNAs by adult nurse bees, leading to specific effects on gene expression during larval development. 71,72 In theory, packaging could also occur in a manner that has been selected for cross-kingdom communication. In addition, incidental inclusion of miRNA into exosomes or cell-free ribonucleoprotein complexes will occur during the processes of digestion.…”