Abstract
Recombination establishes the chiasmata that physically link pairs of homologous chromosomes in meiosis, ensuring their balanced segregation at the first meiotic division and generating genetic variation. The visible manifestation of genetic crossing-overs, chiasmata are the result of an intricate and tightly regulated process involving induction of DNA double-strand breaks and their repair through invasion of a homologous template DNA duplex, catalysed by RAD51 and DMC1 in most eukaryotes. We describe here a RAD51-GFP fusion protein that retains the ability to assemble at DNA breaks but has lost its DNA break repair capacity. This protein fully complements the meiotic chromosomal fragmentation and sterility of Arabidopsis rad51, but not rad51 dmc1 mutants. Even though DMC1 is the only active meiotic strand transfer protein in the absence of RAD51 catalytic activity, no effect on genetic map distance was observed in complemented rad51 plants. The presence of inactive RAD51 nucleofilaments is thus able to fully support meiotic DSB repair and normal levels of crossing-over by DMC1. Our data demonstrate that RAD51 plays a supporting role for DMC1 in meiotic recombination in the flowering plant, Arabidopsis.
Highlights
Meiosis is the specialised cell division essential for sexual reproduction that halves the chromosome number in the production of gametes
Meiotic recombination is initiated by programmed DNA double strand breaks (DSBs), which are resected to generate 39 singlestranded DNA overhangs that are bound by specialised recombinases
We describe here a RAD51-Green Fluorescent Protein (GFP) fusion protein that has lost its DNA break repair capacity but retains the ability to assemble at DNA breaks in the plant, Arabidopsis - fully complementing the meiotic chromosomal fragmentation and sterility of rad51 mutants, and this depends upon DMC1
Summary
Meiosis is the specialised cell division essential for sexual reproduction that halves the chromosome number in the production of gametes. It is characterised by one round of DNA replication followed by two successive divisions, resulting in the production of 4 haploid nuclei from a single mother cell. In contrast to the mitotic cell divisions of development and growth, meiosis necessitates the recognition and coordinated segregation of pairs of homologous chromosomes, a function ensured by meiotic recombination in the majority of studied eukaryotes (reviews by [1,2]). The crucial invasion step of meiotic recombination requires the co-operation of the RAD51 and DMC1 recombinases. DMC1 is only required in meiosis while RAD51 is essential for both mitotic and meiotic recombination [8,9,10,11]
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