Abstract Detail

Hybrids and Hybridization

Kinser, Taliesin [1], Smith, Ronald [2], Lawrence , Amelia H [3], Smith, Gregory [2], Puzey, Joshua [4].

Endosperm development of the triploid bridge to a Mimulus allohexaploid: insights into genomic imprinting .

The endosperm of angiosperms has not only provided essential advantages related to their success, but also is perhaps their most epigenetically intriguing tissue. This transient ephemeral tissue acts as a conduit of nutrients and hormones between the maternal plant and developing embryo and does not provide a genetic contribution to the next generation, even though it is sexual and thus contains both maternal and paternal genomes. The genomic and epigenomic balance between maternal and paternal genomes is critical to proper development of the endosperm (and thus the seed), and is defined by genomic imprinting.
Genomic imprinting is an epigenetic phenomenon where the expression of certain genes is predominantly contributed by one parent and not the other and only occurs in angiosperms and viviparous mammals. Perturbation of imprinting can be fatal to the developing seeds and typically occurs from dosage imbalances or divergent imprinting patterns that can occur rapidly between closely related species. Inter-ploidy and inter-species hybridizations are a common method to study imprinting patterns and their driving genomic and evolutionary mechanisms. Both types of hybridization events can lead to similar endosperm abnormalities which traditionally are associated to similar underlying mechanisms. The most widely attributed evolutionary theory to these studies is the kin (or parental) conflict model, which predicts that sexual conflict arises through contrasting mating strategies of parental alleles, eventually establishing imprinted states. While there is evidence supporting this theory, not all studies provide such support, and there is still very little known about the processes, particularly evolutionary, behind genomic imprinting in angiosperms.
We investigated a recent, naturally occurring, asymmetric hybridization system between two species of Mimulus (Phrymaceae): the diploid, M. guttatus, and tetraploid, M. luteus. Thus, this hybridization is both inter-ploidy and inter-species. We have studied histology, germination rates, transcriptomes, and methylomes of parent seeds and seeds from reciprocal hybrid crosses. Here, we report the developmental abnormalities driving germination rates in hybrid seeds. We also show differing imprinting patterns between the two species and how these patterns reveal Dobzhansky-Muller like incompatibilities in their hybrids. We examine subgenome-specific imprinting patterns, how they relate to broader epigenetic patterns, and their implications to the establishment of allopolyploids. Finally, we find unique imprinting patterns in this system, and we discuss our findings in a broader context related to evolutionary drivers underlying genomic imprinting.

1 - College of William & Mary, 540 Landrum Dr., Williamsburg, Virginia, 23185, United States
2 - College of William and Mary, Applied Science, Williamsburg, VA, USA
3 - College of William & Mary, Biology, 540 Landrum Dr., 110 Sadler Center, Williamsburg, Virginia, 23185, United States
4 - College Of William And Mary, Biology Dept., 540 Landrum Dr., Williamsburg, VA, 23185, United States

Keywords:
genomic imprinting
hybridization barrier
Mimulus
Endosperm
allopolyploidy
subgenomes
RNA-Seq
bisulfite sequencing
histology.

Presentation Type: Oral Paper
Session: 10, Hybrids and Hybridization
Location: 101/Mayo Civic Center
Date: Monday, July 23rd, 2018
Time: 2:00 PM
Number: 10003
Abstract ID:562
Candidate for Awards:Margaret Menzel Award