Competition between meiotic and apomictic pathways during ovule and seed development results in clonality

Abstract

SummaryMeiotic and apomictic reproductive pathways develop simultaneously in facultative aposporous species, and compete to form a seed as a final goal. This developmental competition was evaluated in tetraploid genotypes of Paspalum malacophyllum in order to understand the low level of sexuality in facultative apomictic populations.Cyto-embryology on ovules, flow cytometry on seeds and progeny tests by DNA fingerprinting were used to measure the relative incidence of each meiotic or apomictic pathway along four different stages of the plant's life cycle, namely the beginning and end of gametogenesis, seed formation and adult offspring.A high variation in the frequencies of sexual and apomictic pathways occurred at the first two stages. A trend of radical decline in realized sexuality was then observed. Sexual and apomictic seeds were produced, but the efficiency of the sexual pathway dropped drastically, and exclusively clonal offspring remained.Both reproductive pathways are unstable at the beginning of development, and only the apomictic one remains functional. Key factors reducing sexuality are the faster growth and parthenogenetic development in the aposporous pathway, and an (epi)genetically negative background related to the extensive gene de-regulation pattern responsible for apomixis. The effects of inbreeding depression during post-fertilization development may further decrease the frequency of effective sexuality.

Apomixis frequency under stress conditions in weeping lovegrass (Eragrostis curvula)

“…notatum and by Carman [34] in Boechera ; in Boechera , most ovules fail to produce seeds under stress conditions and most seeds are formed apomictically. Moreover, Hojsgaard et al [35] demonstrated that aposporous embryo sacs develop faster than sexual ones, as they skip meiosis. Thus, the key factor that leads to the reduction in the number of sexually produced progeny would be the faster growth of embryos derived by the aposporous pathway [35].…”

“…Moreover, Hojsgaard et al [35] demonstrated that aposporous embryo sacs develop faster than sexual ones, as they skip meiosis. Thus, the key factor that leads to the reduction in the number of sexually produced progeny would be the faster growth of embryos derived by the aposporous pathway [35]. In aposporous plants, apomixis and sexuality can coexist and compete in the same egg, generally reducing the frequency of sexually derived progeny [35].…”

“…Thus, the key factor that leads to the reduction in the number of sexually produced progeny would be the faster growth of embryos derived by the aposporous pathway [35]. In aposporous plants, apomixis and sexuality can coexist and compete in the same egg, generally reducing the frequency of sexually derived progeny [35]. In diplosporous plants, residual sexuality is less frequent, as the archespore cell must choose one developmental pathway.…”

Interspecific hybrids between Paspalum plicatulum and P. oteroi: a key tool for forage breeding

“…In other species of the genus, it was already observed a drastic decline of the real expression of sexuality when it was assessed at different stages of development, from megagametogenesis through mature ovules, mature seeds, and the subsequent progeny. It seems that there is some biological disadvantages of sexual embryo sacs or sexually formed seeds in relation to apomictic development (Rebozzio et al, 2011;Hojsgaard et al, 2013).…”

Review Apomixis in cassava: advances and challenges

“…It has been investigated in various crops, other than cassava (Manihot esculenta Crantz), since the 1940s by many authors (Gustafsson, 1946;Brown and Emery, 1958;Nygren, 1967;Nogler, 1984;Hanna and Bashaw, 1987;Asker and Jerling, 1992;Savidan, 1992;Grimanelli et al, 2001;Koltunow and Grossniklaus, 2003;Ozias-Akins, 2006;Yudakova, 2009;Tucker et al, 2012;Hojsgaard et al, 2013). It has been studied in 400 species within 300 genera and 40 plant families of Angiosperms (Carman, 1997;Singh et al, 2011).…”