Cell-to-cell communication between Arabidopsis female gametes
Jian-Jun Wu, Xiong-Bo Peng, Wen-Wei Li, Rui-He, Hai-Ping Xin, Meng-Xiang Sun^*

College of Life Science, Wuhan University, Wuhan, China, 430072.
^*Corresponding Author：Tel: (+8627) 68756170; E-mail: mxsun@whu.edu.cn

Abstract
Gametic specification is a key step in fertilization and embryogenesis. Cell-to-cell communication in embryo sacs is thought to regulate the development of female gametes in flowering plants, but the details remain poorly understood. Here, we report a novel gene, GAMETE CELL DEFECTIVE 1 (GCD1) that expressed at high levels in gametophytes and is essential for final maturation of the female gametes. Using Arabidopsis gcd1 mutants, we found that final maturation of the egg and central cells is not required for double fertilization but is necessary for embryogenesis initiation and endosperm development. Furthermore, a previously unrecognized, mitochondrion-dependent signal originating from central and egg cells reciprocally promotes maturation of the partner (egg or central) cell. This signal controls the final maturation of egg and central cells necessary for embryogenesis initiation and early endosperm development. Our findings confirm that cell-to-cell communication is important in functional specification of female gametic cells and demonstrate the critical role of female gametic maturation in seed setting.

Key Words: cell-to-cell communication; gamete; embryogenesis; endosperm; Arabidopsis