Lignocellulose is a major component of plant biomass. Its decomposition
is crucial for the terrestrial carbon cycle. Microorganisms are
considered as primary decomposers and evidence increases that some
invertebrates may also decompose lignocellulose. We investigated the
taxonomic distribution and evolutionary origins of GH45 cellulases in a
collection of soil invertebrate genomes and found that these genes are
common in springtails and oribatid mites. Phylogenetic analysis revealed
that cellulase genes were acquired early in the evolutionary history of
these groups. Domain architectures and predicted 3D enzyme structures
indicate that these cellulases are functional. Patterns of presence and
absence of these genes across different lineages prompt further
investigation into their evolutionary and ecological benefits. The
ubiquity of cellulase genes suggests that soil invertebrates may play a
role in lignocellulose decomposition, independently from microorganisms.
Understanding the ecological and evolutionary implications might be
crucial for understanding soil food webs and the carbon cycle.