The evolutionary origin of animal cellulose synthase

Area of Science:

• Biochemistry
• Evolutionary Biology
• Marine Biology

Background:

• Urochordates are unique among animals for producing cellulose, a structural polysaccharide typically found in plants and bacteria.
• Cellulose biosynthesis occurs within complex multi-enzyme structures, with cellulose synthase as the core catalytic component.

Purpose of the Study:

• To identify and characterize the cellulose synthase gene in the urochordate Ciona intestinalis.
• To investigate the evolutionary origin of cellulose synthesis in animals, specifically exploring the possibility of horizontal gene transfer.

Main Methods:

• Bioinformatic analysis to identify homologs of cellulose synthase genes.
• Gene cloning and characterization of the Ciona intestinalis cellulose synthase gene (Ci-CesA).
• Whole-mount in situ hybridization to determine the spatiotemporal expression of Ci-CesA during embryonic development.

Main Results:

• A novel gene, Ci-CesA, was identified in Ciona intestinalis, featuring a fusion of cellulose synthase and cellulase domains with no known animal homologs.
• Evidence suggests a lateral gene transfer of a bacterial cellulose synthase gene into the urochordate lineage, potentially occurring over 530 million years ago.
• Ci-CesA expression in Ciona intestinalis embryos was observed in patterns consistent with in vivo cellulose synthesis.

Conclusions:

• Urochordates likely utilize a laterally acquired gene for cellulose synthesis, representing an analogous process to that found in other taxa.
• The discovery of Ci-CesA provides insights into the unique evolutionary path of cellulose production in the animal kingdom.
• This finding highlights the dynamic nature of gene evolution and the significant impact of horizontal gene transfer.