Meiotic Recombination and Pairing

Meiosis is the specialized cellular program by which a diploid germline cell gives rise to haploid gametes for reproduction. Its successful execution includes recognition and pairing of homologous maternal and paternal chromosomes (homologs) and establishment of inter-homolog recombinational interactions (crossover/chiasmata) that create the physical linkages required for their correct segregation. Errors in segregation lead to extra or missing chromosomes in gametes (aneuploidy), a major cause of human pregnancy failure and dozens of recurrent congenital disorders (such as trisomy 21), as well as sterility in animal and plants. Moreover, meiotic recombination is a major force of evolution: it can create new and advantageous genetic combinations, but it can also break down existing favorable ones. The frequency and distribution of crossovers dictate therefore, which traits are inherited together and which ones are re-assorted to produce new allelic combinations on which selection can act. However, the mechanisms responsible for crossover frequency and spatial patterning remain poorly understood. To investigate the players involved, we use genetics, genomics, molecular biology and high-resolution cytology approaches to identify the genetic factors responsible for chromosome segregation defects and the mechanisms controlling the number and the distribution of crossovers in two powerful cytological systems: the filamentous fungus Sordaria macrospora and the plant Arabidopsis thaliana.