Asynapsis and desynapsis in plants

Abstract

The pairing of chromosomes also known as synapsis is essential for facilitating crossing over and recombination of genes during prophase-I and segregation of homologous chromosomes during anaphase-I of meiosis. Mutations in genes controlling synapsis affect normal pairing of homologues during prophase-I are give rise to synaptic mutants. The first synaptic mutants were discovered in maize and since then have been reported in large number of plant species. These synaptic mutants show complete or partial lack of chromosome pairing during meiosis. Asynapsis is the complete failure of homologous chromosomes to pair or synapse during the first meiotic division, whereas, desynapsis is a condition where homologous chromosomes pair or synapse normally at the beginning of prophase, but later fail to maintain this association in the subsequent stages of meiosis and thus separate prematurely. Both asynapsis and desynapsis have been found to play significant role in origin of popyploids via formation of 2n gametes. The meiotic disturbance due to asynapsis and desynapsis also leads to the formation of various types of aneuploids.