Abstract
Lignocellulose, as the key structural component of plant biomass, is of
recalcitrant structure and is difficult to degrade. Meanwhile, the
improper handling of plant residues is accelerating the process of
global warming. Interestingly, we noticed that the xylophagous beetle,
Trypoxylus dichotomus has a significant ability to decompose
lignocellulosic biomass. However, no study has been conducted to
elucidate the digestion mechanism from a genome-wide aspect for this
beetle. Based on sequencing and assembling, the draft genome size of
T. dichotomus is 636.27 Mb, with 95.37% scaffolds anchored onto
10 chromosomes. The phylogenetic results indicated that T.
dichotomus and its closely related scarabaeid species Onthophagus
taurus split from each other in the early Cretaceous. Furthermore, two
digestive gene families (Trypsin and Enoyl-(Acyl carrier protein)
reductase) have experienced significant expansion, accounting for the
high degradation efficiency of lignocellulose. Additionally, the
collinearity analysis revealed that chromosome breakages and
rearrangements occur in the evolution of T. dichotomus due to
chromosomes 6 and 8 of T. dichotomus being intersected with
chromosomes 2 and 10 of Tribolium castaneum respectively. As
suggested by the larval intestinal transcriptome comparative analyses,
the digestive ability of midgut is much stronger than that of hindgut,
even though susceptible to different food habits. This study reported
the well-assembled and annotated genome of this rhinoceros beetle,
providing genomic and transcriptomic bases for further understanding the
functional mechanism and evolutionary history of lignocellulolytic
digestion of the beetle.