Large genetic screens for gynogenesis and androgenesis haploid inducers in Arabidopsis thaliana failed to identify mutants

Abstract

Gynogenesis is a process in which the embryo genome originates exclusively from female origin, following embryogenesis stimulation by a male gamete. In contrast, androgenesis is the development of embryos that contain only the male nuclear genetic background. Both phenomena are of great interest in plant breeding as haploidization is an efficient tool to reduce the length of breeding schemes to create varieties. Although few inducer lines have been described, the genetic control of these phenomena is poorly understood. We developed genetic screens to identify mutations that would induce gynogenesis or androgenesis in Arabidopsis thaliana. The ability of mutant pollen to induce either gynogenesis or androgenesis was tested by crossing mutagenized plants as males. Seedlings from these crosses were screened with recessive phenotypic markers, one genetically controlled by the female genome and another by the male genome. Positive and negative controls confirmed the unambiguous detection of both gynogenesis and androgenesis events. This strategy was applied to 1,666 EMS-mutagenised lines and 47 distant Arabidopsis strains. While an internal control suggested that the mutagenesis reached saturation, no gynogenesis or androgenesis inducer was found. However, spontaneous gynogenesis was observed at a frequency of 1/10,800. Altogether, these results suggest that no simple EMS-induced mutation in the male genome is able to induce gynogenesis or androgenesis in Arabidopsis.

State-of-the-art and novel developments of in vivo haploid technologies

“…This principle may be applied in crops too, as targeted protein degradation by the 26S-proteasome was successfully demonstrated in Nicotiana tabacum (Baudisch et al 2018 ). The identification of genes other than CENH3 which could be used to trigger the formation of haploids is challenging, as a large genetic screen for haploidy inducers in A. thaliana has failed to identify any suitable mutants (Portemer et al 2015 ).…”

Genome and transcriptome architecture of allopolyploid okra (Abelmoschus esculentus)

“…Such natural haploids, of which a dwarf form of cotton ( Gossypium ) was discovered in 1920 as the first haploid angiosperm with half the normal chromosome complement (Dunwell, 2010), are assumed to result from asexual egg cell (gynogenetic) reproduction (Noumova, 2008). We took advantage of the fact that the diploid hybrid cultivar has a green recessive petiole female parent and a red dominant petiole male (Figure S1) (Portemer et al ., 2015). Offspring with the green petiole trait lacks the dominant paternal allele and hence can be used as a diagnostic marker for identifying haploid offspring.…”

The HEM Lines: A New Library of Homozygous Arabidopsis thaliana EMS Mutants and its Potential to Detect Meiotic Phenotypes

“…The first generation plants (M1) were selfed and the next generation (M2) was crossed to a haploid inducing strain (the CENH3 Tailswap line) to obtain haploid descendants ( Ravi and Chan, 2010 ). M3 haploid plants were visually identified due to the absence of trichomes conferred by the gl1 mutation ( Portemer et al, 2015 ) and reproduced by self-fertilization, which spontaneously produced diploid seeds (M4). Using this approach, we expected to obtain virtually completely homozygous mutant lines.…”

“…To generate the single seed descent (SSD) collection, we applied ethyl methanesulfonate (EMS) to wild type A. thaliana accession Col-0 as described in ( Portemer et al, 2015 ). Seeds were incubated for 17 h at room temperature with gentle agitation in 5 mL of 0.3% (v/v) EMS.…”