The composition and function of the honeydew secreted by Ericerus pela as deduced from metabolome and transcriptome data

Author of the article:ZHAO ZunLing；YU Shu-Hui；ZHOU Wen-Wu；ZHU ZengRong；GUO ZhongJian；YANG Pu

Author's Workplace：1. Research Institute of Resource Insects, Chinese Academy of Forestry, Key Laboratory of Cultivating and Utilization of Resource Insects of State Forestry Administration, Kunming 650224, China; 2. School of Agronomy and Life Sciences, Kunming University, Kunming 650224, China; 3. Institute of Insect Sciences, Zhejiang University, Hangzhou 310058, China; 4. Institute of Life Sciences, Jiangsu University, Zhenjiang 212000, China

Key Words：Ericerus pela; honeydew; transcriptome analysis; metabolomics analysis; gene family contraction

Abstract：[Objectives]  Female Ericerus pela can secrete a considerable amount of honeydew during the incubation period. We previously found that this honeydew was prone to contamination by certain fungi. However, the biological significance of the honeydew secreted by female E. pela is still largely unclear. This study aimed to understand the composition of the honeydew secreted by E. pela, and provide an overview of gene expression in female adults during this period. We hope the results will lead to a deeper understanding of the biological significance of honeydew secretion by E. pela. [Methods]  The transcriptome of incubating female E. pela period was sequenced and the metabolome of the honeydew secreted by females was analyzed. [Results]  The single greatest component of honeydew was maltitol, followed by galactositol, trehalose, triose and other sugars. Honeydew also contained a small amount of various amino acids, fats, vitamins, and other metabolites or secondary metabolites. Combining the transcriptome and metabolomic data revealed that the main pathways were “metabolic”, “carbon” and “biosynthesis of amino acids”. The gene family related to ‘N-glycan biosynthesis’, and another containing the gene Q96JB1 with the corresponding metabolites citrate, orotate and L-glutamate, were contracted. [Conclusion]  The main components of the honeydew secreted by E. pela are not beneficial for parasitic biological control agents or for mutualism with other insects. Some gene families related to the components of honeydew have been contracted. These results show that the honeydew secreted by E. pela contains unnecessary metabolites, or may be harmful to female E. pela.