Activation of CYCD7;1 in the central cell and early endosperm overcomes cell-cycle arrest in the Arabidopsis female gametophyte, and promotes early endosperm and embryo development.
In angiosperms, double fertilization of the egg and central cell of the megagametophyte leads to the development of the embryo and endosperm, respectively. Control of cell cycle progression in the megagametophyte is essential for successful fertilization and development. Central cell-targeted expression of the D-type cyclin CYCD7;1 (end CYCD7;1) using the imprinted FWA promoter overcomes cycle arrest of the central cell in the Arabidopsis female gametophyte in the unfertilized ovule, leading to multinucleate central cells at high frequency. Unlike FERTILIZATION-INDEPENDENT SEED (fis) mutants, but similar to lethal RETINOBLASTOMA-RELATED (rbr) mutants, no seed coat development is triggered. Unlike the case with loss of rbr, post-fertilization end CYCD7;1 in the endosperm enhances the number of nuclei during syncytial endosperm development and induces the partial abortion of developing seeds, associated with the enhanced size of the surviving seeds. The frequency of lethality was less than the frequency of multinucleate central cells, indicating that these aspects are not causally linked. These larger seeds contain larger embryos composed of more cells of wild-type size, surrounded by a seed coat composed of more cells. Seedlings arising from these larger seeds displayed faster seedling establishment and early growth. Similarly, two different embryo-lethal mutants also conferred enlarged seed size in surviving siblings, consistent with seed size increase being a general response to sibling lethality, although the cellular mechanisms were found to be distinct. Our data suggest that tight control of CYCD activity in the central cell and in the developing endosperm is required for optimal seed formation.
Cardiff School Biosciences, Cardiff University, Sir Martin Evans building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
Emily
E
Sornay
Cardiff School Biosciences, Cardiff University, Sir Martin Evans building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.|Institut Jean-Pierre Bourgin, INRA Centre de Versailles-Grignon, Route de Saint-Cyr, 78026, Versailles, Cedex, France.
Céline
C
Forzani
Cardiff School Biosciences, Cardiff University, Sir Martin Evans building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.|Facultad de Ingenieria, Universidad de Ibagué, Calle Barrio Ambalá, Ibagué, 730002, Colombia.
Manuel
M
Forero-Vargas
Cardiff School Biosciences, Cardiff University, Sir Martin Evans building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
Walter
W
Dewitte
Cardiff School Biosciences, Cardiff University, Sir Martin Evans building, Museum Avenue, Cardiff, CF10 3AX, Wales, UK.
James A H
JA
Murray
D017360:Arabidopsis / Q000196:embryology* / Q000235:genetics*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D059447:Cell Cycle Checkpoints / Q000235:genetics / Q000502:physiology; D056625:Endosperm / Q000196:embryology / Q000378:metabolism; D018506:Gene Expression Regulation, Plant; D056771:Ovule / Q000196:embryology / Q000235:genetics; D012639:Seeds / Q000235:genetics / Q000378:metabolism
D029681:Arabidopsis Proteins
Arabidopsis; D-type cyclins; cell cycle; central cell; endosperm; seed size