Comparison Between Worker-and Queen Development Based On The Analysis Of Microbiome And Transcriptome In Bombus Terrestris

Caste determination is a phenomenon in which individuals of the same sex have different morphological,physiological and behavioral characteristics in social insects.In bumblebees,the queen and worker bees are both female,but their morphology are different.The causes of developmental changes in queen and worker bees are not yet clear.We explored the morphological changes of worker and queen bees during the larval development stage from two aspects:the gut microbes and gene expression in Bombus terrestris.The main results as follows:（1）Morphological changes of worker and queen bees in larvaeThrough biological observation and morphological measurement,we compared the morphological development and feeding times of worker and queen larvae at different ages.The results showed that the larval development of workers and queens was 9 days and 11 days respectively.There was no significant difference in weight and head capsule of 1-4 day-old larvae between workers and queens（p>0.05）,while the queen larvae were significantly larger than worker larvae at 5 day-old larvae（p<0.01）.Worker and queen larvae in 1-4 day-old larvae had lower feeding times,and there was no significant difference of feeding times between the workers and queens in 5-7 day-old larvae,and after 8 day-old larvae,the queen larvae received more feeding times than workers.（2）Analysis of microbiota during the development of worker and queen beesHere,we explored gut microbiota from four stages(early instar larvae:1st instar;mid instar larvae:5^thinstar;late instar larvae:9^thinstar;and adults:7^thday)of worker and queen bees using the full-length 16S r RNA sequencing technology.The results showed that the alpha diversity of the worker and queen bee was similar in early and mid instar larvae,but there was a significant difference in late larvae and adult,which was mainly reflected in 3 phyla and 2 genera,specifically Cyanobacteria,Proteobacteria,Firmicutes,Snodgrassella,and Lactobacillus,which may play a role in the development of worker and queen bees.（3）Analysis of gene expression during the development of worker and queen beesWe compared the differentially expressed genes（DEGs）between worker and queen bees at the larvae and adult stages.The number of DEGs showed a trend of increasing,then decreasing,and finally increasing again,with a higher number of DEGs at mid-stage larvae and adult bees.GO and KEGG enrichment analysis showed that more pathways were enriched in fat regulation,hormone regulation,protein digestion and absorption,and amino acid metabolism.In addition,candidate genes Kr-h1 and Vg were related to caste determination of worker and queen bees.Finally,the WGCNA analysis showed that a total of 107 candidate genes were related to larval weight.GO and KEGG enrichment showed that the candidate genes were mainly related to fat metabolism and hormone regulation.This study showed that the developmental characteristics were different in worker and queen larvae,with a developmental time of 9 days for worker larvae and 11 days for queens.The size of queens was significantly larger than that of workers at 5-day-old larvae,but there was no difference in feeding times.Microbiota showed that the richness and abundance were significant difference at 9-day-old larva between workers and queens.Transcriptome showed that the number of DEGs was most at the 5-day-old larvae between workers and queens.In addition,candidate genes Kr-h1 and Vg related to caste determination of worker and queen bees.The discovery of the differential bacteria and genes between worker and queen bees play an important role in studying the caste determination of bumblebees.