Evolution of distinct expression patterns for engrailed paralogues in higher crustaceans (Malacostraca)

Area of Science:

• Developmental Biology
• Evolutionary Biology
• Genetics

Background:

• The segment-polarity gene engrailed is highly conserved in arthropods.
• Its expression domain is typically in the posterior segment portion.

Purpose of the Study:

• To investigate the expression patterns of engrailed homologues in crustaceans.
• To compare these patterns with those in insects.

Main Methods:

• Utilized pan-specific antibodies Mab4D9 and Mab4F11.
• Cloned partial cDNAs of two engrailed genes (Ps-en1, Ps-en2) from Porcellio scaber.
• Performed whole-mount in situ hybridization for gene expression analysis.
• Conducted phylogenetic analysis of engrailed sequences.

Main Results:

• Mab4D9 and Mab4F11 showed distinct expression patterns in crustaceans (Porcellio scaber, Procambarus clarkii) compared to insects.
• Mab4D9 detected signals in posterior segments, appendages, trunk, and CNS.
• Mab4F11 detected signals primarily in CNS and peripheral nervous system (PNS) neurons.
• Two engrailed genes (Ps-en1, Ps-en2) exhibited distinct expression patterns in late embryogenesis.
• Ps-en1 expressed in CNS and epidermis; Ps-en2 in lateral aspects and limbs.
• Phylogenetic analysis suggests relationships between crustacean and insect engrailed genes.

Conclusions:

• Crustacean engrailed gene expression differs from insects, suggesting evolutionary divergence.
• The presence of multiple engrailed paralogues (Ps-en1, Ps-en2) in crustaceans contributes to expression diversity.
• Phylogenetic data supports evolutionary links between specific engrailed genes in crustaceans and insects.