Desynapsis and spontaneous trisomy in jute (Corchorus olitorius L.)

Meiosis-driven genome variation in plants

Meiosis includes two successive divisions of the nucleus with one round of DNA replication and leads to the formation of gametes with half of the chromosomes of the mother cell during sexual reproduction. It provides a cytological basis for gametogenesis and nheritance in eukaryotes. Meiotic cell division is a complex and dynamic process that involves a number of molecular and cellular events, such as DNA and chromosome replication, chromosome pairing, synapsis and recombination, chromosome segregation, and cytokinesis. Meiosis maintains genome stability and integrity over sexual life cycles. On the other hand, meiosis generates genome variations in several ways. Variant meiotic recombination resulting from specific genome structures induces deletions, duplications, and other rearrangements within the genic and non-genic genomic regions and has been considered a major driving force for gene and genome evolution in nature. Meiotic abnormalities in chromosome segregation lead to chromosomally imbalanced gametes and aneuploidy. Meiotic restitution due to failure of the first or second meiotic division gives rise to unreduced gametes, which triggers polyploidization and genome expansion. This paper reviews research regarding meiosis-driven genome variation, including deletion and duplication of genomic regions, aneuploidy, and polyploidization, and discusses the effect of related meiotic events on genome variation and evolution in plants. Knowledge of various meiosis-driven genome variations provides insight into genome evolution and genetic variability in plants and facilitates plant genome research.

Mutant genes affecting higher plant meiosis

That meiosis is conditioned by a large number of genes majority of which are present in a dominant state, is evidenced by the detection of numerous monogenic recessive mutant genes which affect the premeiotic, meiotic and post-meiotic course of events. These genes are site- and stage-specific, and a few are sex specific. Of these, the most prevalent are the mutant genes affecting male meiosis and causing male sterility (ms genes) and those inhibiting synapsis and chiasma formation (synaptic genes) and leading to gametic sterility. Majority of the mutant genes affect the entire chromosomal complement but a few influence only specific chromosomes of a complement so that the chromosomes behave differentially within a genome of the same species. Some mutant genes alter chromosome form and function, others modify integrity, degree of spiralization, movement and migration of chromosomes. Their cytogenetic behaviour, genetic significance and breeding utility are described and discussed.