Genetic Dissection of Apomixis in Dandelions Identifies a Dominant Parthenogenesis Locus and Highlights the Complexity of Autonomous Endosperm Formation

Abstract

Apomixis in the common dandelion (Taraxacum officinale) consists of three developmental components: diplospory (apomeiosis), parthenogenesis, and autonomous endosperm development. The genetic basis of diplospory, which is inherited as a single dominant factor, has been previously elucidated. To uncover the genetic basis of the remaining components, a cross between a diploid sexual seed parent and a triploid apomictic pollen donor was made. The resulting 95 triploid progeny plants were genotyped with co-dominant simple-sequence repeat (SSR) markers and phenotyped for apomixis as a whole and for the individual apomixis components using Nomarski Differential Interference Contrast (DIC) microscopy of cleared ovules and seed flow cytometry. From this, a new SSR marker allele was discovered that was closely linked to parthenogenesis and unlinked to diplospory. The segregation of apomixis as a whole does not differ significantly from a three-locus model, with diplospory and parthenogenesis segregating as unlinked dominant loci. Autonomous endosperm is regularly present without parthenogenesis, suggesting that the parthenogenesis locus does not also control endosperm formation. However, the high recovery of autonomous endosperm is inconsistent with this phenotype segregating as the third dominant locus. These results highlight the genetic complexity underlying apomixis in the dandelion and underline the challenge of introducing autonomous apomixis into sexual crops.

A PARTHENOGENESIS allele from apomictic dandelion can induce egg cell division without fertilization in lettuce

“…The i34 LOP mutant still made autonomous endosperm (Fig. 1b), which is consistent with the observation that autonomous endosperm is independent of parthenogenesis 24 . Pollination of i34 with a diploid sexual led to tetraploid offspring (Fig.…”

Mendelian segregation for parthenogenetic embryo development at the diploid level in the flowering plant Erigeron

“…The presence of the locus initiates development of both the egg cell and fusion nucleus in the absence of fertilization. This dual function is consistent with previous observations in Erigeron (Noyes et al, 2007) and also for aposporous Hieracium (Koltunow et al, 2011; but see Henderson et al, 2017; Van Dijk et al, 2020). Both are members of the Asteraceae wherein apomicts with autonomous endosperm formation may be common.…”

Skipping sex: A nonrecombinant genomic assemblage of complementary reproductive modules

“…Therefore, functional shifts in components of sexual reproduction can be linked to genomic regions behaving as supergenes (in which even individual genes can be identified) rather than to complete haplomes. [78,[104][105][106][107][108][109] The above-stated conditions and the developmental and molecular…”