Functional analysis of the Arabidopsis thaliana meiotic proteins AtPCH2 and AtCHR24

摘要

In the past decade Arabidopsis thaliana has become an important system for studying meiosis in flowering plants. The identification of meiotic mutants has provided an important approach to studying plant meiosis. The availability of the Arabidopsis genome sequence together with developments in proteomics and bioinformatics provides an additional route for the identification of meiotic proteins and analysis of their functional interrelationships. This study has used a proteomics approach to identify a member of the SWI2/SNF2 chromatin remodelling gene family (Atchr24). Although a variety defects was observed in Atchr24 male meiocytes cytogenetic, at least two T-DNA insertion lines on this gene appear normal. Secondly, this research has also used a bioinformatics approach to identify a potential orthologue of Pch2/TRIP13 in Arabidopsis. PCH2 (Pachytene checkpoint 2) is a member of the AAA+ ATPase family of proteins. This study reveals that AtPCH2 plays an essential role in the controlled formation of meiotic crossovers (COs). Cytogenetic analysis of two Atpch2 T-DNA insertion lines revealed a high frequency of univalents at MI. The number of chiasmata (COs) is reduced to ~ 70% of wild-type (WT). Genetic analysis revealed that Atpch2 has significantly weaker CO interference than WT leading to a redistribution of COs along the chromosomes. The recombination defect is accompanied by incomplete chromosome synapsis. Immunolocalisation of the chromosome axis protein AtASY3 and cohesin, AtSYN1 appears normal. However in contrast to WT, AtASY1 co-localises with the synaptonemal protein AtZYP1 in ii ududAtpch2 rather than becoming depleted in regions of synapsis and the meiotic progression of Atpch2 is delayed during pachytene by ~5 hours. These observations suggest a defect in remodeling of the chromosome axes and highlight how this process is essential for normal CO control.ud