Correspondence:
Xiao-Lin Chu or Quan-Guo Zhang, College of Life Sciences, Beijing Normal University, Beijing 100875, P. R. China; Tel: +86 10 58802308; Fax: +86 10 58809899; Email:chuxl@mail.bnu.edu.cn, orzhangqg@bnu.edu.cn
Author contributions: XLC, AB and QGZ designed the study. XLC performed the experiment. XLC and QGZ analysed the data. All authors wrote the manuscript.
Data accessibility statement: All data and R code used in the analysis will be made available on Figshare (https://doi.org/10.6084/m9.figshare.19552216).