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Title: Regulation of Arabidopsisembryo and Endosperm Development by the Polypeptide Signaling Molecule CLE8

item FIUME, E - University Of California
item Fletcher, Jennifer

Submitted to: The Plant Cell
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2012
Publication Date: 3/16/2012
Citation: Fiume, E., Fletcher, J.C. 2012. Regulation of Arabidopsisembryo and Endosperm Development by the Polypeptide Signaling Molecule CLE8. The Plant Cell. 24:1000-12.

Interpretive Summary: The plant seed is a major source of nutrition for humans and therefore is of tremendous agricultural value. Normal seed formation requires the coordinated development of the plant embryo and the surrounding nutritional endosperm tissue, but very little is known about the molecules that communicate developmental information between these tissues in the growing seed. The Arabidopsis CLE8 gene encodes a small protein that is exported from the cells in which it is produced and sends a signal to neighboring cells to affect their behavior. We have found that CLE8 is made specifically in embryo and endosperm cells during early seed formation. We have determined that CLE8 functions to control aspects of early embryo cell division and patterning as well as endosperm growth. We also demonstrated that CLE8 turns on the expression of the WOX8 transcription factor gene, and that these two molecules promote seed growth and overall seed size. Our research shows that CLE8 genes plays an essential role in coordinating the early development of the seed, and reveals the existence of a seed-specific signaling pathway as a potential target for manipulation to benefit agriculture.

Technical Abstract: The plant seed is a major nutritional source for humans as well as an essential embryo development and dispersal unit. To ensure proper seed formation, fine spatial and temporal coordination between the embryo, endosperm, and maternal seed components must be achieved. However, the intercellular signaling pathways that direct the synchronous development of these tissues are poorly understood. Here we show that the Arabidopsis thaliana peptide ligand CLAVATA3/EMBRYO SURROUNDING REGION-RELATED8 (CLE8) is exclusively expressed in young embryos and endosperm, and that it acts cell and non-cell autonomously to regulate basal embryo cell division patterns, endosperm proliferation, and the timing of endosperm differentiation. CLE8 positively regulates expression of the transcription factor gene WUSCHEL-LIKE HOMEOBOX8 (WOX8), and together CLE8 and WOX8 form a signaling module that promotes seed growth and overall seed size. These results demonstrate that seed development is coordinated by a secreted peptide ligand that plays a key early role in orchestrating cell patterning and proliferation in the embryo and endosperm.