INVESTIGATOR: Schnable, P. S.; Nikolau, B. J.

PERFORMING INSTITUTION:
AGRONOMY
IOWA STATE UNIVERSITY
AMES, IOWA 50011

CIS- AND TRANS-MODIFIERS OF MEIOTIC RECOMBINATION IN MAIZE

OBJECTIVES: The a1-sh2 interval of the maize genome will be used as a model to test the following hypotheses: 1) most recombination occurs in genes; 2) intergenic recombination clusters into hot spots; 3) cis-acting factors afusters into hot spots; 3) cis-acting factors affect the distribution of recombination events; 4) trans-acting factors affect the distribution of recombination events.

APPROACH: To identify DNA sequence polymorphisms and to define the locations of genes, a 50-kb portion of the a1-sh2 interval that is recombinationally hyperactive will be sequenced from both parents of a mapping population from which a large collection of recombination events have been isolated. The DNA sequence polymorphisms identified between the two parents will be used to physically map the recombination breakpoints relative to each other and genes within the a1-sh2 interval, and thereby test hypotheses 1 and 2. Previously, it has been demonstrated that cis factors in the a1-sh2 interval can influence the rate of recombination across this interval. To identify cis factors that influence rates of recombination, large numbers of recombinants are being isolated from a series of stocks that are heterozygous for unique configurations of the a1-sh2 interval. Subsequently, the recombination breakpoint associated with each recombinant will be physically mapped. Comparisons of the distributions of recombination breakpoints from each configuration of the a1-sh2 interval will test hypothesis 3. Previously three genetic backgrounds have been identified that differentially affect the rate of recombination across a sequence-identical a1-sh2 interval. Hypoence-identical a1-sh2 interval. Hypothesis 4 will be tested by physically mapping the recombination breakpoints associated with the over 100 recombinant chromosomes isolated from each of these three genetic backgrounds

NON-TECHNICAL SUMMARY: Meiotic recombination is a central mechanism by which genetic diversity is generated. Such genetic diversity is fundamental to evolution and to many of the strategies used to improve crop species. Considerable evidence indicates that meiotic recombination does not occur evenly throughout plant genomes; rather, recombination The 140-kb, multi-genic a1-sh2 interval from maize is being used as a model to determine the relative contributions of genic and non-genic recombination. Because this approach identifies recombination hot spots without making prior assumptions regarding their molecular nature, it will begin to test two hypotheses formulated to explain the fact that large regions of the genome experience very different rates of recombination. In addition, this research will utilize unique genetic stocks to separate the genetic effects of cis or trans modifiers of recombination. Stocks that carry unique configurations of the a1-sh2 interval will be used to characterize the effects of specific cis-acting factors on recombination rates. Finally, another set of genetic stocks that carry trans-acting modifiers that modulate rates of recombination across the a1-srates of recombination across the a1-sh2 interval, will be used to test the hypothesis that trans-acting modifiers can affect the distribution of recombination breakpoints

PROJ. CONTACT:

Name: Good, C.
Phone: 515-294-4544
Fax: 515-294-2909
Email: cgood@iastate.edu