17:	Isolation and Characterization of SYN1 and SYN2, RAD21-Like Genes Essential for Meiosis and Mitosis in Arabidopsis.

Authors:	Dong, Fugui(A)Cai, Xue(A)Bai, Xuefang(A)Peirson, Brenda, N.(A)Makaroff, Christopher, A.(A)
Affiliations:	(A): Department of Chemistry and Biochemistry, Miami University
Presenter:	Makaroff, Christopher A., makaroca@muohio.edu

The proper condensation, pairing and segregation of chromosomes is central to mitosis and meiosis. A T-DNA tagged, male sterile mutant of Arabidopsis, syn1, which exhibits alterations in meiotic synapsis, has been characterized to identify genes/proteins associated with chromosome pairing in plants. Lines homozygous for syn1 are male- and female-sterile and show defects in chromosome condensation and pairing beginning at leptonema of meiosis I. Fragmentation of chromosomes is observed at metaphase I. SYN1 has been isolated and found to exhibit similarity to S. pombe RAD21 and RAD21-like proteins, which are required for chromosome condensation and sister chromatid cohesion during mitosis. Alternative promoters/splicing results in the production of two SYN1 transcripts. One transcript is expressed at low levels in most tissues, while the other is expressed only in prebolting buds. A second Arabidopsis RAD21-like gene SYN2 has been cloned and sequenced. It is approximately 16% identical to other RAD21 proteins with the highest sequence conservation found at the amino- and carboxy-termini (46% and 38%, respectively). SYN2 transcripts are present at low levels in all tissues, suggesting that it may be involved in chromosome condensation and cohesion during mitosis. Studies investigating the role of SYN1 and SYN2 in meiosis and mitosis, respectively will be presented.