Centromeres

Cereal comparative mapping studies in the mid-1990’s suggested that centromeric sequences might be conserved across the cereal genomes.  We hypothesized that centromere sites would contain conserved centromere elements, and that centromeres may play a key role in the initial chromosome pairing process in meiosis. We confirmed this hypothesis by being the first to identify a conserved element (CCS1) found in all cereal centromeric regions (Aragon-Alcaide et al, 1996).

This facilitated the characterisation of the centromere regions of any cereal. Our analyses also revealed that cereal genome evolution involved the breakage and fusion of chromosomes at centromere sites.  We then studied centromere behaviour at meiosis, using cell biology approaches. In a series of publications culminating in the first Nature paper on wheat in over 10 years, we showed that in wheat (and rice), centromeres associate prior to meiosis, and that this pairing process enables chromosomes to be presorted for meiosis (Martinez-Perez et al, 2003, Aragon Alcaide et al, 1997, Martinez-Perez et al, 1999, Martinez-Perez et al, 2000, Martinez-Perez et al, 2001). These observations were eventually translated to the yeast model microbe.

In situ hybridization of CCS1 to wheat centromeres

 

 

Two consecutive sections through a wheat x rye anther in the absence of Ph1 prior to meiosis
Wheat centromeres are labelled green.  The images show that the 21 wheat centromeres have reduced to 7 centromere sites in every cell.  (See summary of centromere behaviour in “Meiosis gallery”).

John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK

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