Comparative Transcriptomics Analysis Reveals Rusty Grain Beetle’s Aggregation Pheromone Biosynthesis Mechanism in Response to Starvation

TL;DR

This study identifies genes involved in the biosynthesis of aggregation pheromones in the rusty grain beetle under starvation stress.

Contribution

The study reveals specific genes and pathways involved in pheromone biosynthesis in response to starvation in the rusty grain beetle.

Findings

2665 genes were significantly differentially expressed, with 2029 down-regulated in starved beetles.

Genes related to the MVA and FAS pathways were identified as directly involved in pheromone biosynthesis.

Juvenile hormone and insulin-related genes were found to be depressed in starved beetles, suggesting roles in pheromone regulation.

Abstract

Pheromones, such as sex pheromones, aggregation pheromones, and alarm pheromones, are the basis for insect aggregation, mating, and other behaviors. Compared with the structures of sex pheromones, those of aggregation pheromones are more complex, especially in cucujoid grain beetles, which produce macrocyclic lactones as aggregation pheromones. So far, there is limited research studying the biosynthesis of macrocyclic lactones at the molecular level. Two aggregation pheromone components of the rusty grain beetle, Cryptolestes ferrugineus, have been identified to be biosynthesized via the mevalonate (MVA) pathway and fatty acid synthesis (FAS) pathway, with their productions affected by starvation. Therefore, we conducted a comparative transcriptomics analysis of hypothetical pheromone production sites in C. ferrugineus under starvation stress. Additionally, significantly enriched metabolic pathways and down-regulated genes directly involved in the biosynthesis and regulation of aggregation pheromones via the MVA and FAS pathways, respectively, were identified, as well as some juvenile hormone (JH)- and insulin-related genes, which are of great significance for elucidating the synthesis and regulatory mechanisms of cucujoid grain beetle pheromones.

Pheromones are the basis of insect aggregation, mating, and other behaviors. Cucujoid grain beetles produce macrocyclic lactones as aggregation pheromones, yet research on their biosynthesis at the molecular level remains limited. The rusty grain beetle, C. ferrugineus, is an important economic species in China. Although two aggregation pheromone components have been identified, their suspected biosynthesis via the MVA pathway and the FAS pathway lacks molecular elucidation. Previous evidence supports that starvation affects the production of aggregation pheromones. Therefore, we constructed comparative transcriptome libraries of pheromone production sites in C. ferrugineus under starvation stress and identified genes related to pheromone biosynthesis and hormone regulation. A total of 2665 genes were significantly differentially expressed, of which 2029 genes were down-regulated in starved beetles. Putative C. ferrugineus genes directly involved in pheromone biosynthesis were identified, as well as some genes related to the juvenile hormone (JH) pathway and the insulin pathway, both of which were depressed in the starved beetles, suggesting possible functions in pheromone biosynthesis and regulation. The identification of genes involved in macrolide lactone biosynthesis in vivo holds great significance, aiding in the elucidation of the synthesis and regulatory mechanisms of cucujoid grain beetle pheromones.

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