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Identifying determinants of hybridisation barriers in Arabidopsis

Reference	BB/D001234/1
Principal Investigator / Supervisor	Professor Roderick Scott
Co-Investigators / Co-Supervisors
Institution	University of Bath
Department	Biology and Biochemistry
Funding type	Research
Value (£)	185,098
Status	Completed
Type	Research Grant
Start date	01/11/2005
End date	31/10/2008
Duration	36 months

Abstract

The transfer of desirable traits from wild relatives to crop plants is often complicated by the operation of various types of hybridisation barrier. Post-fertilisation barriers are frequently associated with abnormal development of the endosperm, which leads to seed abortion. We have shown that in Arabidopsis species this type of barrier is due to genomic imprinting. Others have suggested imprinting also accounts for triploid block in which crosses between diploid and tetraploid plants of the same species fail due to abnormal endosperm development. We established that several ecotypes of Arabidopsis operate tetraploid rather than triploid block, and that this is indeed due to imprinting. Recently we discovered that the Columbia ecotype in contrast operates triploid block and therefore contains a modifier of imprinting, which we have mapped to chromosome 2. Here we propose to fine map and identify the modifier locus using STAIR lines. Since few ecotypes have been tested we will also survey a panel of ecotypes for triploid block to establish whether the behaviour of Columbia is aberrant. This will require the generation of tetraploids using colchicine doubling. We will then determine the action of the modifier gene(s) in Arabidopsis ecotypes that operate triploid or tetraploid block, and finally attempt to correlate expression of known imprinted genes in different ecotyopes with crossing behaviour. This information will be useful in understanding the nature of the post-fertilization type of hybridization barrier, and offer a means to improve crop breeding.

Summary

Conventional plant improvement often uses hybridisation to transfer desirable traits from one species or variety to another. However, such crosses may fail due to the operation of a post-fertilisation hybridisation barrier associated with abnormal development of the endosperm, a part of the seed that nourishes the embryo. We have shown that in Arabidopsis species this type of barrier is due to genomic imprinting, an mechanism that affects certain genes in the endosperm so that they are expressed from chromosomes inherited from only one parent. Other researchers have suggested imprinting also accounts for the phenomenon of triploid block in which crosses between diploid and tetraploid plants of the same species fail due to abnormal endosperm development, and therefore do not produce the expected triploid plants. We established that several common populations(ecotypes) of Arabidopsis operate tetraploid rather than triploid block, and that this is indeed due to imprinting. Recently we discovered that the widely used Columbia ecotype in contrast operates triploid block and therefore contains a modifier of imprinting which we have mapped to one of the 5 chromosomes of Arabidopsis. Here we propose to identify the modifier locus. This should allow us to determine how it functions. Since few ecotypes have been tested we will also survey more ecotypes for triploid block to establish whether the behaviour of Columbia is in fact unusual. We will then determine the action of the modifier gene(s) in Arabidopsis plants that operate triploid or tetraploid block, and finally attempt to correlate expression of imprinted genes in different ecotypes with their crossing behaviour. This information will be useful in understanding the nature of the post-fertilisation type of hybridisation barrier, and offer a means to improve crop breeding.

Committee	Closed Committee - Plant & Microbial Sciences (PMS)
Research Topics	Plant Science
Research Priority	X – Research Priority information not available
Research Initiative	X - not in an Initiative
Funding Scheme	X – not Funded via a specific Funding Scheme

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