Modularity and evolutionary constraints in a baculovirus gene regulatory network

Area of Science:

• Virology
• Systems Biology
• Genomics

Background:

• Understanding complex biological systems requires insight into regulatory network structures.
• Viral life cycles offer unique models for studying host-parasite network dynamics.
• The Anticarsia gemmatalis multiple nucleopolyhedrovirus (AgMNPV) genome contains 152 open reading frames (ORFs).

Purpose of the Study:

• To analyze the ordered cascade of AgMNPV gene expression.
• To elucidate the structure and characteristics of the AgMNPV gene regulatory network (GRN).

Main Methods:

• Analysis of gene expression patterns across viral life cycle stages.
• Construction and topological analysis of the AgMNPV transcription GRN for 149 ORFs.
• Comparative analysis of gene expression, genetic diversity, and genome organization with related baculoviruses.

Main Results:

• Observed earlier gene expression onset, particularly for DNA replication genes, compared to other baculoviruses.
• Identified a modular GRN topology with five distinct communities, compartmentalizing functionally related genes.
• Found conserved gene arrangement in overlapping transcripts among related baculoviruses, indicating genome organization principles.
• Demonstrated that core conserved functions exhibit expression synchronicity and reduced genetic diversity, correlating with GRN importance.

Conclusions:

• The AgMNPV GRN, despite its reduced scale, exhibits modularity and key characteristics similar to complex cellular organisms.
• Modularity appears to be a fundamental feature of biological gene regulatory networks.
• Gene expression patterns and network topology provide insights into evolutionary constraints and genome organization in viruses.