3.5 | Expanded or contracted gene families related to the adaptation of B. schroederi
To better understand the adaptation to the specific habitat and intestinal environment of the giant panda, we analyzed the expanded and contracted genes in B. schroederi compared with three roundworms (A. suum , P. univalens and T. canis) .
We identified expanded gene families with functions involved in striated muscle contraction (GO:0006941), nematode larval development (GO:0002119), larval feeding behavior (GO:0030536), chitin metabolic process (GO:0006030) and actin cytoskeleton organization (GO:0030036). The most significantly enriched GO term was the straight muscle contraction, which was largely due to the highly significant expansion of the actin family (Fig. 3a, 3d). KEGG enrichment showed that the number of genes involved in metabolic pathways, including drug metabolism (metabolism of xenobiotics by cytochrome P450, ko00980;P <0.01) and autoimmunity (ko05130, ko05100;P <0.01), exhibited significant changes (Fig. 3a). We observed an expansion of the gene family involved in positive regulation of eating behavior (Fig. 3b). Finally, we found that B. schroederi has 654 unique annotated proteins, which were mainly enriched in the synthesis and recycling pathways of essential amino acids especially the degradation of valine, leucine and isoleucine (ko00280, P <0.01; Fig. 3c).