Meiosis is essential for all sexually reproducing organisms and the studies described here will further our understanding of this process not only in maize but in all organisms. The mechanism of meiosis is a topic of major medical interest since inaccurate chromosome segregation (aneuploidy) during meiosis is causal in several congenital malformations, a major cause of premature termination of pregnancy, and of poor gamete production in humans. Our goal is to understand the mechanism of chromosome segregation during meiosis, particularly how homologous chromosomes pair and synapse. Maize is the only organism where there is a large collection of mutants that affect meiosis, and it is possible to do superb cytology. Entrance into meiotic prophase is under control of a cell cycle dependent switch, ameiotic 1 (am1) whose function is required to convert a mitotic to a meiotic cell cycle. The function of aml will be studied at a molecular, biochemical and cytological level. We will use expression microarrays to determine whether meiotic gene expression is altered in aml mutant alleles. Chromosome structure will be studied in absence of first division 1 (afd1) nuclei where RAD51 installation is very severely reduced. For various afdl alleles, we will correlate extent of RAD51 installation with extent of leptotene/zygotene chromosome remodeling. We will make anti-AFD1 antibody to immuno-purify AFD1 interacting proteins, and for localization of FD1 on meiotic chromosomes. We propose that RAD51 complexes are required for both the homology search and recombination. To analyze potential recombination defects in our 20-desynaptic mutants, we will use antibodies against key recombination pathway components such as SPO 11, RAD51, BLM or MSH4 and MLH1 to classify their position in the pairing/recombination pathway based on deficiencies in protein complex distribution. We will make double mutants between members of various classes of RAD51 loci deficient mutants to analyze potential epistatic interactions. We will further cytologically and molecularly characterize the three mutants poor homologous synapsis1 (phs1), desynapticCS (dsyCS), and segregation II (seglI) that are severely deficient in RAD51 foci and determine whether they are deficient in a step required to load RAD51 complexes onto chromosomes. We will clone dsyCS and seglI, using transposon-tagging strategies, characterize their function, and if time permits, clone other genes defective in later stages of the pairing/recombination pathway.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
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Genetics Study Section (GEN)
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Carter, Anthony D
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University of California Berkeley
Schools of Arts and Sciences
United States
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Golubovskaya, Inna N; Wang, C J Rachel; Timofejeva, Ljudmilla et al. (2011) Maize meiotic mutants with improper or non-homologous synapsis due to problems in pairing or synaptonemal complex formation. J Exp Bot 62:1533-44
Wang, Chung-Ju Rachel; Carlton, Peter M; Golubovskaya, Inna N et al. (2009) Interlock formation and coiling of meiotic chromosome axes during synapsis. Genetics 183:905-15
Gustafsson, Mats G L; Shao, Lin; Carlton, Peter M et al. (2008) Three-dimensional resolution doubling in wide-field fluorescence microscopy by structured illumination. Biophys J 94:4957-70
Golubovskaya, Inna N; Hamant, Olivier; Timofejeva, Ljuda et al. (2006) Alleles of afd1 dissect REC8 functions during meiotic prophase I. J Cell Sci 119:3306-15
Jin, Ye; Mancuso, Joel J; Uzawa, Satoru et al. (2005) The fission yeast homolog of the human transcription factor EAP30 blocks meiotic spindle pole body amplification. Dev Cell 9:63-73
Hamant, Olivier; Golubovskaya, Inna; Meeley, Robert et al. (2005) A REC8-dependent plant Shugoshin is required for maintenance of centromeric cohesion during meiosis and has no mitotic functions. Curr Biol 15:948-54
Franklin, Amie E; Golubovskaya, Inna N; Bass, Hank W et al. (2003) Improper chromosome synapsis is associated with elongated RAD51 structures in the maize desynaptic2 mutant. Chromosoma 112:17-25
Jin, Ye; Uzawa, Satoru; Cande, W Z (2002) Fission yeast mutants affecting telomere clustering and meiosis-specific spindle pole body integrity. Genetics 160:861-76
Bass, H W; Riera-Lizarazu, O; Ananiev, E V et al. (2000) Evidence for the coincident initiation of homolog pairing and synapsis during the telomere-clustering (bouquet) stage of meiotic prophase. J Cell Sci 113 ( Pt 6):1033-42
Kaszas, E; Cande, W Z (2000) Phosphorylation of histone H3 is correlated with changes in the maintenance of sister chromatid cohesion during meiosis in maize, rather than the condensation of the chromatin. J Cell Sci 113 ( Pt 18):3217-26

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