Regulation of Isoprenoid Pheromone Biosynthesis in Bumblebee Males

Abstract

Males of the closely related species Bombus terrestris and Bombus lucorum attract conspecific females by completely different marking pheromones. MP of B. terrestris and B. lucorum pheromones contain mainly isoprenoid (ISP) compounds and fatty acid derivatives, respectively. Here, we studied the regulation of ISP biosynthesis in both bumblebees. RNA-seq and qRT-PCR analyses indicated that acetoacetyl-CoA thiolase (AACT), 3-hydroxy-3-methylglutaryl-CoA reductase (HMGR), and farnesyl diphosphate synthase (FPPS) transcripts are abundant in the B. terrestris labial gland. Maximal abundance of these transcripts correlated well with AACT enzymatic activity detected in the LG extracts. In contrast, transcript abundances of AACT, HMGR, and FPPS in B. lucorum were low, and AACT activity was not detected in LGs. These results suggest that transcriptional regulation plays a key role in the control of ISP biosynthetic gene expression and ISP pheromone biosynthesis in bumblebee males.

Exploring complex pheromone biosynthetic processes in the bumblebee male labial gland by RNA sequencing

“…The mRNA enrichment of several Bombus terrestris MP‐biosynthetic gene candidates in the LG in comparison to the FB, ie fatty acid desaturases (Buček et al ., ), lipase (Brabcová et al ., ), fatty acid synthase (Žáček et al ., ) and enzymes of terpene biosynthesis (Prchalová et al ., ), which was previously demonstrated by qRT‐PCR, is in good agreement with the herein analysed Bombus terrestris LG and FB RNA‐seq data sets. To further increase plausibility of the Bombus terrestris FB and LG transcriptomic data sets and to validate their comparison to publicly available Bombus terrestris transcriptomic data (Sadd et al ., ), we selected five genes representing various MP‐biosynthetic pathways and protein classes that we found were considerably enriched in the LG and measured their mRNA abundances in male FB, LG and QH using qRT‐PCR.…”

“…Employing the RNA‐seq data discussed in this paper, Prchalová et al . () identified a complete set of isoprenoid biosynthetic candidate genes: acetoacetyl‐CoA thiolase, 3‐hydroxy‐3‐methylglutaryl coenzyme A synthase, HMGR, mevalonate kinase, phosphomevalonate kinase, diphosphomevalonate decarboxylase, isopentenyl diphospate isomerase, bifunctional farnesyl diphosphate synthase capable of sequential biosynthesis of geranyl diphosphate and farnesyl diphosphate, and geranylgeranyl diphosphate synthase. In addition, the researchers confirmed the high LG‐expression of these enzymes by qRT‐PCR (Prchalová et al ., ).…”

“…The genes involved in biosynthesis of the isoprenoid backbone were identified in the Bombus terrestris labial gland (LG) and fat body (FB) by Prchalová et al . (). The colour‐coded expression values across tissues are based on log 2 ‐transformed reads per kilobase of exon model per million mapped reads (RPKM) values.…”

“…Sesquiterpene and diterpene derived compounds constituting the majority of MPs in Bombus terrestris and also in Bombus hortorum and Bombus pratorum (Kullenberg et al ., ) are produced de novo in the LG (Žáček et al ., ) via enzymes of the isoprenoid pathway (Prchalová et al ., ). de novo terpenoid pheromone biosynthesis has been extensively studied in male bark beetles (Coleoptera: Ips spp.…”

“…Established protocols for year‐round breeding of Bombus terrestris provides a continuous source of specimens of defined ages and physiological condition. This allows for the investigation of temporal changes in MP composition, along with other aspects of Bombus terrestris physiology and behaviour (Šobotník et al ., ; Žáček et al ., ; Jiroš et al ., ; Jarau et al ., ; Brabcová et al ., ; Buček et al ., ; Prchalová et al ., ).…”