Epigenetic Control of Apomixis: A New Perspective of an Old Enigma

Abstract

Apomixis is an asexual mode of reproduction through seeds in plant which results in clonal multiplication of the maternal plant due to the absence of meiosis and fertilization of egg cell. It has been reported to occur in >300 plant species belonging to >35 angiosperm families. Apomixis has been common in polyploid grasses, and poorly represented in the crop species. If apomixis could be incorporated in crop plants, its impact on agriculture could be overwhelming because apomixis promises to maintain hybrid vigor in the progenies over the generations. However, engineering apomixis in crop plant is considered to be one of the greatest challenges mainly because of the limited knowledge about the genetic basis and regulatory mechanisms underlying the apomictic seed development. The genetic and molecular bases of apomixis is still intriguing from both developmental and evolutionary perspectives. Coexistence of apomixis and sexuality in an individual plant suggests that apomixis is reversibly superimposed upon sexuality. Epigenetic control of apomixis is an attractive and emerging theory being investigated with growing support from the studies on sexual plants wherein mutations in epigenetic pathway genes resulted into apomixis-like phenotypes. With the growing evidences for epigenetic variations as important regulator of stress-associated genes, and the evidence for upregulation of stress-associated metabolite (spermidine and polyamine) biosynthesis, epigenetics is likely to be in focus of future studies on apomixis. Therefore, apomixis could be introgressed into crop plants in future by switching-off the sexual pathway to an apomixis-like route by transferring the candidate gene(s). However, flexibility to switch apomixis/sexuality on and off would be necessary for crop breeding purposes.