Minisymposium 10: Cell Division

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Abs # M1002: PARTING DANCERS, a founding member of a novel gene family in plants, is required for the homologous recombination during meiotic prophase I in Arabidopsis

Presenter:	Wijeratne, Asela J.       Contact Presenter
Authors	Wijeratne, Asela J. (A) (B)  Chen, Changbin  (B)   Zhang, Wei  (B)   Timofejeva, Ljudmilla  (B) (C)  Copenhaver, Gregory P. (D)   Ma, Hong  (A) (B)
Affiliations:	(A): Intercollege Graduate Program in Plant Physiology, the Pennsylvania State University, University Park, PA 16802, USA (B): Department of Biology and the Huck Institutes of the Life Sciences, the Pennsylvania State University, University Park, PA 16802, USA (C): Department of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, Tallinn 19086 Estonia (D): Department of Biology, the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina 27599-3280, USA

Interactions of homologous chromosomes during meiotic prophase I play an important role for precise chromosome segregation into four gametes. These interactions include the pairing of two homologs, followed by the polymerization of the synaptonemal complex (synapsis) between the homologs. By the time the synaptonemal complexes disassemble (desynapsis), homolog recombination has completed, resulting in crossovers. Homologs attached to each other through crossover events are called bivalents and this attachment along with cohesion between sister chromatids ensures the correct segregation of homologs during anaphase I. In yeast, there are two genetically separable pathways for the formation of crossovers, interference sensitive and interference insensitive. Despite identification of several key genes that regulate the formation of crossover pathway intermediates, only few genes are known for the resolution of double Holliday junctions, the last key intermediate of interference sensitive crossover pathway. In recent years, Arabidopsis has emerged as an excellent model organism for studying meiotic process. The Arabidopsis mutant, parting dancers (ptd), which is defective in male meiosis, produced meiocytes with reduced number of crossovers at diakinesis stage of prophase I and the remaining crossovers showed a random distribution; therefore, the ptd mutant is defective in formation of interference sensitive crossovers. A genetic analysis indicated that PTD might function in a same pathway as the MSH4 and MER3/RCK genes, which are important for crossover formation in Arabidopsis. However, unlike mer3/rck, ptd contained normal level of synaptonemal complexes and late recombination nodules at pachytene stage, suggesting that ptd was defective in crossover formation at a slightly later stage compared to mer3/rck. Furthermore, PTD appeared to be the founding member of a gene family conserved in plants, but PTD showed a limited sequence similarity to ERCC1, which form a heterodimeric complex with an endonuclease, XPF. An analysis of recombination frequency in the ptd mutant using CFP and dsRED tagged markers will also be discussed. According to the results, in connection with the current model of homologous recombination in meiosis, PTD might promote the formation of crossovers in interference sensitive pathway possibly by regulating the resolution of double Holliday junction intermediates in favor of crossover formation.