Trehalose is the primary circulating sugar in insects, has long been regarded as a metabolic substrate required for energy production during high-demand physiological stages such as flight and metamorphosis.
This study reveals that E2F/Dp, a transcription factor complex, links trehalose metabolism to muscle development by regulating genes involved in cell-cycle progression and developmental tissue formation.
Metamorphosis is among the most energy-intensive and tightly coordinated phases in an insect’s life. During this transition, larval tissues are dismantled and rebuilt into adult structures, including highly organised flight muscles essential for survival. While the role of hormones and developmental genes in this process is well established, the contribution of metabolism, particularly how energy availability influences muscle formation, has remained unclear.
A recent study at CSIR-NCL by Dr Rakesh Joshi and his team on the cotton bollworm moth, Helicoverpa armigera, now provides important insight into this connection. The work demonstrates that trehalose metabolism does far more than supply energy during metamorphosis; it actively regulates the genetic machinery required for muscle development.
Trehalose is the primary circulating sugar in insects, functioning as a major energy reservoir. During development, trehalose is converted into glucose, which enters glycolysis, the central pathway responsible for cellular energy production. To investigate the significance of this pathway, researchers disrupted genes involved in trehalose synthesis, specifically trehalose 6-phosphate synthase/phosphatase (TPS/TPP), along with paramyosin (Prm), a structural muscle protein.
Insects with impaired trehalose metabolism failed to complete normal eclosion and displayed fragmented, poorly organised muscle fibres. Microscopic analysis revealed disorganized muscle architecture, indicating that disruption of metabolic balance directly affects muscle formation during metamorphosis.
To understand the underlying biochemical changes, the researchers performed metabolic profiling. They observed broad depletion of glycolytic intermediates and key cellular cofactors, indicating a major reduction in energy production. Simultaneously, AMP levels increased significantly, indicating cellular energy stress. Together, these findings showed that trehalose-derived glucose flux is essential for sustaining glycolysis and maintaining energetic homeostasis during insect development.
Beyond metabolism, the study showed an unexpected link between cellular energetics and gene regulation. Transcriptomic analysis showed significant downregulation of the transcription factor complex E2F/Dp, accompanied by reduced expression of cyclins and cyclin-dependent kinases involved in cell-cycle control. This suggest that energy stress caused by impaired trehalose metabolism disrupts transcription necessary for proper developmental progression.
Further investigation showed that repression of E2F/Dp reduced the expression of several genes essential for muscle development , including Myocyte enhancer factor (Mef2), paramyosin (Prm) and myosin heavy chain (MHC). As these proteins are critical for muscle assembly and contractile function, their reduced expression explains the defective muscle phenotype observed in the silenced insects.
The computational analyses, including gene regulatory network and promoter binding site analysis, identified E2F-binding motifs within promoters of both trehalose metabolism genes and myogenic genes. This highlights a coordinated metabolic-transcriptional regulatory system, where nutrient availability and energy balance directly influence developmental gene expression.
To further validate this relationship, the researchers supplemented the insects’ diet with trehalose. Remarkably, trehalose feeding partially restored metabolic balance and rescued the expression of several myogenic genes and TFs, even in TPS/TPP- and E2F/Dp-silenced insects. The recovery of muscle-related transcription strongly supports the role of trehalose metabolism as a central regulatory node linking energy metabolism with developmental signaling.
The study provides new insights into insect physiology by demonstrating that metabolism is not merely a passive support system for development. Instead, metabolic pathways actively communicate with transcriptional networks to determine whether sufficient energy resources are available for tissue formation and differentiation.
Beyond its developmental significance, the work may also hold relevance for agricultural science. As Helicoverpa armigera is a major crop pest, understanding vulnerabilities in its metabolic and developmental pathways could potentially contribute to future pest management strategies targeting insect growth and metamorphosis.
The findings highlight an emerging theme in biology: metabolism and gene regulation are deeply interconnected. By uncovering how trehalose metabolism governs transcriptional control of muscle development, this study provides a molecular framework linking energy homeostasis, cell-cycle regulation and tissue development during metamorphosis
Trehalose metabolism regulates transcriptional control of muscle development in lepidopteran insects
Sharada Mohite, Tanaji Devkate, Prashant Kalaskar, Prashant Singh, Abhishek Subramanian, Rakesh Shamsunder Joshi