Parallel meta-transcriptome analysis reveals degradation of plant
secondary metabolites by beetles and their gut symbionts
Abstract
Switching to a new host plant is a driving force for divergence and
speciation in herbivorous insects. This process of incorporating a novel
host plant into the diet may require a number of adaptations in the
insect herbivores that allow them to consume host plant tissue that may
contain toxic secondary chemicals. As a result, herbivorous insects are
predicted to have evolved efficient ways to detoxify major plant
defenses and increase fitness by either relying on their own genomes or
by recruiting other organisms such as microbial gut symbionts. In the
present study we used parallel meta-transcriptomic analyses of
Altica flea beetles and their gut symbionts to explore the
contributions of beetle detoxification mechanisms versus detoxification
by their gut consortium. We compared the gut meta-transcriptomes of two
sympatric Altica species that feed exclusively on different host
plant species as well as their F1 hybrids that were fed one of the two
host plant species. These comparisons revealed that gene expression
patterns of Altica are dependent on both beetle species identity
and diet. The community structure of gut symbionts was also dependent on
the identity of the beetle species, and the gene expression patterns of
the gut symbionts were significantly correlated with beetle species and
plant diet. Some of the enriched genes identified in the beetles and gut
symbionts are involved in the degradation of secondary metabolites
produced by plants, suggesting that Altica flea beetles may use
their gut microbiota to help them feed on and adapt to their host
plants.