Prospects and limits of the flow cytometric seed screen – insights from Potentilla sensu lato (Potentilleae, Rosaceae)

Abstract

The flow cytometric seed screen allows for identification of reproductive modes of seed formation and inference of the ploidy of contributing gametes. However, the lack of a mathematical formalization to infer male/female genomic contributions, and the prerequisite of a binucleate female contribution to the endosperm limits its applicability.We evaluated this assumption combining a DNA-based progeny survey with a comparison of the cytology of reproductive pathways co-occurring within single individuals representing 14 Potentilleae species from six phylogenetic lineages.A numerical framework valid for sexual and pseudogamous taxa was developed, enabling quantification of female and male genomes contributing to embryo and endosperm independent of gametophyte origins, numbers of sperm involved and ploidy of parents. The inference strongly depended on accurate peak index estimation. The endosperm of Potentilleae species received a binucleate female contribution in five evolutionary lineages whereas endosperm formation remained uncertain in the Tormentillae. A modified flow cytometric seed screen protocol was developed to cope with low endosperm contents.Evolutionary conservation of a binucleate female contribution to the endosperm suggested wide applicability of flow cytometric seed screen – at least in the Potentilleae. However, alternative progeny surveys and precise embryo/endosperm ploidy estimates are required for a comprehensive understanding of the cytology of seed formation.

Correlations of polyploidy and apomixis with elevation and associated environmental gradients in an alpine plant

“…A remarkably high proportion of tetraploid individuals formed seeds which are, to a varying degree, based on sexual pathways. Facultative apomixis is quite typical for plants reproducing via apospory because apomictic and sexual development run initially in parallel (Asker and Jerling, 1992; Krahulcová et al ., 2004; Dobeš et al , 2013; Klatt et al , 2016). Apospory was observed in R. kuepferi by Burnier et al (2009).…”

“…Like many other facultative apomicts, a single plant can produce both sexual and apomictic seeds within the same flower (Aliyu et al , 2010; Dobeš et al , 2013). To quantify the main mode of reproduction, we determined ploidies of both endosperm and embryo per single seed for each individual.…”

“…Ratios of es: em ploidies were calculated to determine whether a seed has been produced sexually (3:2 ratio) or via apomixis (3:1, 2.5:1, 2:1 ratio). Interpretation of all plausible pathways for development and fertilization of seeds of R. kuepferi (Table 1) have been adopted from the studies by Matzk et al (2000), Talent and Dickinson (2007), Cosendai and Hörandl (2010) and Dobeš et al (2013), and provided the basis for our classification; terminology for designation of ploidy levels follows Greilhuber et al (2005). A threshold of 1.65 es:em ratio was set to discriminate between sexual (lower values) and asexual (higher values) cases.…”

“…However, no study has so far quantitatively compared the proportions of facultative sexual reproduction within and among populations at different elevations and in different parts of the distribution range. Moreover, the full range of pathways of seed formation possible in apomictic plants (Matzk et al , 2000; Dobeš et al , 2013), had never been assessed before in R. kuepferi . For instance, it was so far unknown to which extent tetraploid obligate sexuals or diploid apomicts would contribute to the distribution patterns.…”

Reproductive differentiation into sexual and apomictic polyploid cytotypes in Potentilla puberula (Potentilleae, Rosaceae)

“…The method differentiates between the meiotic and the apomeiotic formation of the embryo sac, the parthenogenetic and zygotic origin of the embryo, and the autonomous vs. pseudogamous development of the endosperm. Recently, FCSS has been extended to calculate male and female genomic contributions to the embryo and endosperm, respectively, in sexual and pseudogamous apomicts (Dobeš et al , 2013). Calculation of the genomic contribution is based on the assumption that endosperms receive a bi-nucleate female contribution, a prerequisite which first can be proven based on cyto-embryological evidence and (molecular marker-aided) progeny surveys (cf.…”