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First published online September 2, 2003
doi: 10.1242/10.1242/dev.00692

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The globby1-1 (glo1-1) mutation disrupts nuclear and cell division in the developing maize seed causing alterations in endosperm cell fate and tissue differentiation

Liliana M. Costa1, Jose F. Gutierrez-Marcos1, Thomas P. Brutnell2, Andrew J. Greenland3 and Hugh G. Dickinson1,*

1 Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK
2 Boyce Thompson Institute for Plant Research, Tower Road, Ithaca, NY 14853, USA
3 Syngenta, Jealott's Hill, Bracknell RG12 6EY, UK



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  		Fig. 1. The glo1-1 kernel phenotype. (A) Ear segregating for glo1-1 mutant kernels (arrow). (B) Germinal faces of a mature wild-type (far left) and three glo1-1 kernels, showing a range of typical mutant phenotypes. (C) glo1-1 uncovered by TB-1La (white arrow). (D) Longitudinal section through a wild-type kernel (far left), kernel with hypoploid (glo1-1/ glo1-1/–) endosperm and hyperploid (glo1-1/+/+) embryo (arrow, middle left), kernel with hypoploid (+/+/–) endosperm and hyperploid (+/+/+) embryo (middle right), and kernel with hyperploid (glo1-1/ glo1-1/+ /+) endosperm and hypoploid (glo1-1/–) embryo (arrow, far right).

 


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  		Fig. 2. Effects of the glo1-1 mutation on early endosperm development. Developing endosperm in (A,C,E) wild-type and (B,D,F) glo1-1 mutants. (A) Wild-type syncytium. (B) Abnormal accumulation of nuclei in glo1-1 basal syncytium (arrow). (C) Wild-type cellularising endosperm with first cell layer formed. (D) glo1-1 endosperm showing abnormal cellularisation in the basal region (arrow). Fully cellular (E) wild-type endosperm and (F) glo1-1 endosperm with constrictions around the apical region (arrow) and abnormal basal endosperm morphology. en, endosperm; nu, nucellus; p, pericarp; z, zygote. Scale bars: 50 µm.

 


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  		Fig. 3. Effects of glo1-1 on embryo and endosperm morphology. Transition-stage embryo in (A) wild-type and (B) glo1-1, showing small, dense cytoplasmic cells (circle) located in the defective suspensor (s). Endosperms (8 dap) in (C,E,G) wild-type and (F,H-J) glo1-1. (C) Wild-type basal endosperm transfer layer (BETL; betl in figure). (D) Two large cells (designated with arrowhead) interrupt the arrangement of the glo1-1 BETL. (E) Wild-type starchy endosperm (SE; se in figure). (F) Disorganised SE in glo1-1 often containing clusters of small cells and enlarged cells. (G) Wild-type aleurone (al). (H,J) Aleurone development in glo1-1: (H) two aleurone layers, (I) abnormal proliferation of aleurone in the glo1-1 apical endosperm and (J) lack of a regular aleurone layer. Additionally, cell wall stubs (arrows) and multinucleate cells (asterisks) were observed in glo1-1 embryos (data not shown) and endosperms (D,F,I,J). Circles highlight areas of interest. e, embryo-proper; esr, embryo surrounding region; pc, placento-chalazal region. Scale bars: 50 µm in A-D,G,H,J; 100 µm in E,F,I.

 


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  		Fig. 4. TEM of glo1-1 endosperms. (A) Endoplasmic reticulum (er) is regularly associated with cell walls (cw) in the wild-type. (B-F) glo1-1 endosperms. (B) Cell walls are often thickened and incomplete in glo1-1. (C) Cell wall stub located in central cytoplasm (cy). (D) Cell with three nuclei (n). (E) Poor cell-cell adhesion (arrow) and multivesicular bodies (mvb). (F) Disrupted starchy endosperm (se) with an aleurone-like cell (al) adjacent to the lacuna (l). Scale bars: 200 nm in A-C,E; 1 µm in D; 10 µm in F.

 


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  		Fig. 5. Effects of glo1-1 on basal endosperm-specific gene expression. mRNA in situ analysis using (A-C) ZmESR and (D,E) a BETL-specific marker (J.F.G.-M., unpublished). (A-C) ZmESR expression (shown in purple, arrows) in (A) 7 dap wild-type endosperm, and in glo1-1 endosperms at (B) 7 dap and (C) 10 dap. BETL-specific gene expression in 10 dap (D) wild-type BETL and (E) glo1-1 basal endosperm, where expression is confined to a single cell (arrow). pBET1-GUS expression (pink) in (F) wild-type and (G) glo1-1 endosperms at 14 dap. Scale bars: 100 µm.

 


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  		Fig. 6. Aleurone cell abnormalities in glo1-1. pVP1-GUS analysis in 10 dap wild-type (A) and glo1-1 endosperms (B-E). GUS expression (pink) highlighting the (A) wild-type aleurone, and (B) glo1-1 aleurone and some cells in the SE (arrows). GUS staining also in glo1-1 basal transfer region (C-E) and in peripheral cells of ectopic cysts (D,E). Scale bars: 100 µm.

 


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  		Fig. 7. Proposed model for BETL specification in wild-type and glo1-1 syncytial endosperms. BETL specification of basal nuclei most probably occurs via positional information by unknown cue(s) either ascending from the maternal tissue (red circles), or already present in the syncytium (green circles), or derived from both. Given the abnormal arrangement of glo1-1 basal nuclei, perhaps not all of them would perceive the positional information to assume BETL identity (blue), hence some nuclei would remain undifferentiated (yellow). Furthermore, we speculate that BETL specification is a determined event (see Discussion); hence, subsequent daughter cells would develop in a lineage-dependent fashion. Broken line indicates endosperm-maternal tissue interface.

 

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© The Company of Biologists Ltd 2003