Ovule development in Arabidopsis: progress and challenge.

Female gametophyte, the central core of the ovule, is a simple seven-celled reproductive structure. Its stereotyped ontogeny provides a traceable model system to study mechanisms controlling cell growth, cell division, cell fate, pattern formation, and perhaps the function of essential genes in plants. An auxin concentration gradient was demonstrated for the first time in the embryo sac to control gametic cell fate. Mutant analysis also indicates a role of RNA processing in the mitotic progression of the gametophytic generation and cell fate determination in the embryo sac. Combined studies of genetics and transcriptome analysis revealed recently that epigenetic pathways play a critical role in female gametophyte development. In addition, the discovery that a large number of small secreted cysteine-rich proteins are enriched in embryo sac is of special interest. Except these insights and progresses, challenge ahead is to reveal the signaling pathways and their interactions that lead to the patterning of the female gametophyte. Copyright Â