When genomes collide: aberrant seed development following maize interploidy crosses.
OBJECTIVE
The results of wide- or interploidy crosses in angiosperms are unpredictable and often lead to seed abortion. The consequences of reciprocal interploidy crosses have been explored in maize in detail, focusing on alterations to tissue domains in the maize endosperm, and changes in endosperm-specific gene expression.


METHODS
Following reciprocal interploidy crosses between diploid and tetraploid maize lines, development of endosperm domains was studied using GUS reporter lines, and gene expression in resulting kernels was investigated using semi-quantitative RT-PCR on endosperms isolated at different stages of development.


RESULTS
Reciprocal interploidy crosses result in very small, largely infertile seeds with defective endosperms. Seeds with maternal genomic excess are smaller than those with paternal genomic excess, their endosperms cellularize earlier and they accumulate significant quantities of starch. Endosperms from the reciprocal cross undergo an extended period of cell proliferation, and accumulate little starch. Analysis of reporter lines and gene expression studies confirm that functional domains of the endosperm are severely disrupted, and are modified differently according to the direction of the interploidy cross.


CONCLUSIONS
Interploidy crosses affect factors which regulate the balance between cell proliferation and cell differentiation within the endosperm. In particular, unbalanced crosses in maize affect transfer cell differentiation, and lead to the temporal deregulation of the ontogenic programme of endosperm development.
Pennington
Paul D
PD
Department of Plant Sciences, South Parks Road, Oxford OX1 3RB, UK.
Costa
Liliana M
LM
Gutierrez-Marcos
Jose F
JF
Greenland
Andy J
AJ
Dickinson
Hugh G
HG
D003433:Crosses, Genetic; D017930:Genes, Reporter; D018745:Genome, Plant; D011003:Ploidies; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012639:Seeds / Q000254:growth & development*; D013213:Starch / Q000378:metabolism; D003313:Zea mays / Q000196:embryology* / Q000235:genetics
D013213:Starch