Hexaploid wheat- Triticum aestivum 2n= 6x= 42 1 2 3 4 5 6 7

A

B

D

abcd

abcd

abcd

Very large chromosomeswith similar gene orders

7A7A

abcd

Homoeologues

abcd

7B 7B

abcd

7D 7D

The Ph1 locus (a dominant locus) restricts pairing to homologuesRiley and Chapman (1958) Nature

The Ph1 locus stabilises wheat,ensuring high fertility

Importance of Ph1 in Breeding

Wheat-rye hybrid

Ph1+

Ph1-

Ph1 stops wheat and wild species chromosomes pairing

A single wheat carrying a deletion of Ph1 locus (ph1b- 70Mb in size) used in breeding- is heavily rearranged

Can we from understanding Ph1 locus, temporary switch Ph1 off in hybrids of elite wheat varieties crossed with wild species?

Wild species of wheat carry important traits fordisease resistance, salt, cold and drought tolerance

A A

B bb

a a

B

homologues homoeologues

Different expression patterns

Homologues and homoeologues replicated at different times as remodelling is slowed- thus will be in different conformations for meiosisAll chromosomes

replicated together

Homoeologuesremodelledtogether

Homologuesprematureremodelling

Ph1+Cdk2 rate limitingremodellingslows

Ph1+

Ph1-

Ph1 story

Ph1 locus is aCdk2-like gene complexCdk2 in humans remodels chromatin for replication

Ph1-Cdk2

Abundant

Drug strategy-needle in haystack?

• How do you activate cdk?

• Inhibit phosphatases which deactivate cdks- increase cdk activity?

Phosphatase inhibitors cause premature condensation and rapid progression through meiotic prophase I in humans and mouse

• Can we inhibit phosphatases to modulate pairing in hybrids?

Can we improve the exploitation the introgression process?

Application?

Ph1+

Wheat x rye hybrid