Expression and functional analysis of TaASY1 during meiosis of bread wheat (Triticum aestivum).
BACKGROUND
Pairing and synapsis of homologous chromosomes is required for normal chromosome segregation and the exchange of genetic material via recombination during meiosis. Synapsis is complete at pachytene following the formation of a tri-partite proteinaceous structure known as the synaptonemal complex (SC). In yeast, HOP1 is essential for formation of the SC, and localises along chromosome axes during prophase I. Homologues in Arabidopsis (AtASY1), Brassica (BoASY1) and rice (OsPAIR2) have been isolated through analysis of mutants that display decreased fertility due to severely reduced synapsis of homologous chromosomes. Analysis of these genes has indicated that they play a similar role to HOP1 in pairing and formation of the SC through localisation to axial/lateral elements of the SC.


RESULTS
The full length wheat cDNA and genomic clone, TaASY1, has been isolated, sequenced and characterised. TaASY1 is located on chromosome Group 5 and the open reading frame displays significant nucleotide sequence identity to OsPAIR2 (84%) and AtASY1 (63%). Transcript and protein analysis showed that expression is largely restricted to meiotic tissue, with elevated levels during the stages of prophase I when pairing and synapsis of homologous chromosomes occur. Immunolocalisation using transmission electron microscopy showed TaASY1 interacts with chromatin that is associated with both axial elements before SC formation as well as lateral elements of formed SCs.


CONCLUSIONS
TaASY1 is a homologue of ScHOP1, AtASY1 and OsPAIR2 and is the first gene to be isolated from bread wheat that is involved in pairing and synapsis of homologous chromosomes.
Molecular Plant Breeding Cooperative Research Centre, School of Agriculture, Food & Wine, The University of Adelaide, Waite Campus, PMB1, Glen Osmond, South Australia, Australia. scott.boden@adelaide.edu.au <scott.boden@adelaide.edu.au>
Scott A
SA
Boden
Nadim
N
Shadiac
Elise J
EJ
Tucker
Peter
P
Langridge
Jason A
JA
Able
D000595:Amino Acid Sequence; D023902:Chromosome Pairing / Q000502:physiology; D032461:Chromosomes, Plant / Q000378:metabolism; D035264:Flowers / Q000235:genetics; D018506:Gene Expression Regulation, Plant; D049469:Meiotic Prophase I / Q000502:physiology*; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000502:physiology*; D016415:Sequence Alignment; D014908:Triticum / Q000166:cytology* / Q000235:genetics / Q000502:physiology; D015854:Up-Regulation
D010940:Plant Proteins