1. Key Laboratory of Agricultural Genetics and Breeding, Agro-biotech Research Center, Shanghai Academy of Agricultural Sciences, 2901 Beidi Road, Shanghai 201106, People's Republic of China, School of Life Science, Shanghai University, 99 Shangda Road, Shanghai 200436, People's Republic of China, and Department of Biological Science and Technology, Nanjing University, 22 Hankou Road, Nanjing 210093, People's Republic of China