Abstract Detail

Hybrids and Hybridization

Hussain, Sidra [1], Winter, David [2], Cox, Murray [1], Soltis, Douglas [3], Soltis, Pamela [4], Tate, Jennifer [5].

Evolution of Cytonuclear Coordination in Tragopogon (Asteraceae) Allopolyploids.

Allopolyploidy is considered one of the major pathways for plant species diversification. In allopolyploids, the duplicated and biparentally inherited nuclear genomes interact with only one set of maternally inherited cytoplasmic (mitochondrial and plastid) genomes, which results in an altered cytonuclear stoichiometry. In this project, we have employed RNA CaptureSeq to examine expression differences of cytonuclear complexes in Tragopogon miscellus allopolyploids along with their diploid parental species, Tragopogon dubius and Tragopogon pratensis, at different developmental stages. These are young, naturally occurring allopolyploids, that have formed multiple times, including reciprocally, hence they offer a window into the potential for repeated evolution of cytonuclear coordination. Using the parental T. dubius draft genome, we developed probes for ~300 loci involved in nuclear-mitochondrial and nuclear-plastid complexes as well as dual-targeted genes. In short- and long-liguled T. miscellus, ~85-92% duplicated nuclear genes/homeologs showed no difference in the total expression level compared to their parent species, at all growth stages. However, only 0.5-3% genes displayed non-additive expression patterns across all growth stages in both polyploid forms except for the mature-age growth stage, where most genes showed parental expression patterns. Among non-additive expression patterns, unbalanced expression level dominance toward the paternal parent, T. pratensis, was observed in long-liguled T. miscellus. Nevertheless, mixed patterns including unbalanced expression level dominance toward either T. pratensis or T. dubius, as well as balanced expression level dominance were found in all populations of short-liguled T. miscellus. In terms of homeolog expression bias, the average percentage of homeologs with biased vs unbiased expression in short- and long-liguled forms was ~51:49 and ~43:57 across all developmental stages, respectively. Among the loci that exhibited biased expression, an unbalanced homeolog expression bias toward T. pratensis was generally observed in both reciprocal forms, but with no maternal bias effect. Also, homeolog expression of ~41-52% of the loci showed parental legacy in populations of short-liguled T. miscellus compared to the long-liguled form, where ~53-55% homeologs in the polyploid displayed their parental expression patterns. Interestingly, a very small number of genes displayed directional homeolog bias as well as cross-specific maternal bias between both reciprocal forms. Furthermore, in terms of homeolog expression bias, homeologs involved in cytonuclear complexes demonstrated no directional bias with respect to developmental stages. These genes which showed either diverse patterns of homeolog expression bias or non-additive expression patterns are annotated to be part of different cytonuclear complexes rather than being enriched to a certain complex. The control genes, which are not involved in cytonuclear interactions, generally showed unbiased expression and followed their parents’ footsteps in case of both homeolog expression bias and total gene expression level. The existence of such flexible and diverse expression patterns in T. miscellus allopolyploids depict the complex role of allopolyploidization in co-regulating the cytonuclear genomes.

1 - Massey University, School of Natural Sciences, Private Bag 11222, Palmerston North, MWT, 4442, New Zealand
2 - Institute of Environmental Science and Research (ESR), Health and Environment, 34 Kenepuru Drive, Kenepuru, Porirua, 5022, New Zealand
3 - University Of Florida, Dept. of Biology, Gainesville, FL, 32611, USA
4 - University Of Florida, Florida Museum Of Natural History, Gainesville, FL, 32611.0, United States
5 - Massey University, School of Natural Sciences, Massey University, Private Bag 11222, Palmerston North, Palmerston North, 4442, New Zealand

Keywords:
allopolyploidy
Cytonuclear interactions
RNA CaptureSeq
Tragopogon miscellus.

Presentation Type: Oral Paper
Number: HH2005
Abstract ID:751
Candidate for Awards:Margaret Menzel Award