* 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.