3.6 | The significant expansion of actin family in
Ascariasis and positive selection genes (PSGs) in B. schroederi
The migration of roundworms is the main cause of VLM (Fig. 4a). Actin
polymerization is controlled by intracellular signals that are mediated
by small GTPases of the Rho family (RhoA , Rac1 , andCdc42 ; Fig. 4c). We observed a very significant expansion of the
actin family in the B. schroederi genome (Fig. 3d). Surprisingly,
the three upstream regulators of actin (Rac1 , ROCK andMLCK ), were under strong positive selection
(P <0.01). ROCK phosphorylates the LIM-kinase
which then phosphorylates cofilin to promote rho-induced actin
cytoskeleton reorganization(Maekawa & M., 1999). These finding suggest
a possible effect on myosin-actin interaction. Using the branch-site
model implemented in PAML, 475 genes in the B. schroederi genome
were found to be under strong positive selection compared with other
three roundworms (Supplementary Data 3a). Compared with three
roundworms, the acetylcholine receptor subunit alpha-type deg-3
(P=6.5×10-3), which is an important drug target(Jones,
Davis, Hodgkin, & Sattelle, 2007), was shown to be under strong
positive selection in the B. schroederi genome (Supplementary
Data 3a).