* Corresponding Authors:
School of Biological Sciences, University of Hong Kong, Pokfulam, Hong
Kong (email: jinwu@hku.hk and
leeckf@hku.hk; phone: +852
2299-0655)
This manuscript is original and has not been published elsewhere, nor is
it currently under consideration for publication elsewhere. We have no
conflicts of interest to disclose and do not involve ethical issue of
human and animals.