The genetic breakdown of sporophytic self‐incompatibility in Tolpis coronopifolia (Asteraceae)

Abstract

Summary Angiosperm diversity has been shaped by mating system evolution, with the most common transition from outcrossing to self-fertilizing.To investigate the genetic basis of this transition, we performed crosses between two species endemic to the Canary Islands, the self-compatible (SC) species Tolpis coronopifolia and its self-incompatible (SI) relative T. santosii. We scored self-compatibility as self-seedset of recombinant plants within two F2 populations.To map and genetically characterize the breakdown of SI, we built a draft genome sequence of T. coronopifolia, genotyped F2 plants using multiplexed shotgun genotyping (MSG), and located MSG markers to the genome sequence. We identified a single quantitative trait locus (QTL) that explains nearly all variation in self-seedset in both F2 populations.To identify putative causal genetic variants within the QTL, we performed transcriptome sequencing on mature floral tissue from both SI and SC species, constructed a transcriptome for each species, and then located each predicted transcript to the T. coronopifolia genome sequence. We annotated each predicted gene within the QTL and found two strong candidates for SI breakdown. Each gene has a coding sequence insertion/deletion mutation within the SC species that produces a truncated protein. Homologues of each gene have been implicated in pollen development, pollen germination, and pollen tube growth in other species.

EbARC1, an E3 Ubiquitin Ligase Gene in Erigeron breviscapus, Confers Self-Incompatibility in Transgenic Arabidopsis thaliana

“…Previous studies have shown that many plant species in Asteraceae are SSI (e.g., Tolpis coronopifolia (Desf.) Biv., S. squalidus) [30,31], while a few are SC (L. sativa and cultivated sunflower). E. breviscapus is a medicinal plant of Asteraceae, which has a significant effect on the treatment of cardiovascular and cerebrovascular diseases [32].…”

Genetic insights into the modification of the pre-fertilization mechanisms during plant domestication

“…GSI has a common molecular basis across many plant families and is probably the ancestral condition for flowering plants (McClure, 2006). In contrast, SSI is present in at least 10 plant families and derives from at least 17 distinct evolutionary origins (Igic et al, 2008;Koseva et al, 2017). In SSI, S-specificity is determined by the genotype of the sporophyte that produced the pollen grain (Sehgal and Singh, 2018).…”

How rapidly do self‐compatible populations evolve selfing? Mating system estimation within recently evolved self‐compatible populations of Azorean Tolpis succulenta (Asteraceae)

“…The floral parts in plants from GRSC and GRBL are smaller than in SI T. succulenta (Crawford et al., 2019; L. Borges Silva & M. Moura, unpubl.) but the “selfing syndrome” (Cutter, 2019; Ornduff, 1969; Slotte et al., 2012) is not nearly as highly developed as in ostensibly more ancient transitions to predominant selfing in Macaronesian Tolpis (Crawford et al., 2008; Koseva et al., 2017; Soto‐Trejo et al., 2013).…”