Abstract Detail



Functional Genetics/Genomics

Ramsey, Adam [1], Mandel, Jennifer [2].

Mitochondrial and plastid genetic variation and phenotypic differentiation in wild carrot, Daucus carota.

Strict uniparental inheritance of organelles and the germline bottleneck experienced by organellar genomes are suggested to limit within individual organellar genetic diversity. This results in homoplasmy, in which all mitochondrial or plastid genomes in an individual are identical. However, uniparental inheritance is not as strict as once believed, and studies have shown that different organellar genomes can be maintained through the germline bottleneck. When biparental inheritance of organelles (even rare instances) occurs between parents with sufficiently different mitochondrial or plastid genomes, a mixture of genomes is created in the offspring, i.e., heteroplasmy. Maternal inheritance of heteroplasmy has been documented in a variety of animals (e.g., Drosophila, mice, and humans) and plants (e.g., Arabidopsis and Silene), so the suggested germline bottleneck is insufficient at maintaining homoplasmy. Nevertheless, heteroplasmy is often regarded as disadvantageous. In humans, heteroplasmy has been associated with several types of mitochondrial diseases, and it is postulated to disrupt cytonuclear interactions. Yet studies have shown that recombination between heteroplasmic variants can rescue incompatibilities between organellar and nuclear genomes, as shown in Nicotiana and Drosophila. Given the prevalence of heteroplasmy within populations and species and across a variety of eukaryotes, questions of its evolutionary importance remain. Here, we present data from a study investigating the phenotypic differentiation and potential fitness effects of heteroplasmy in Daucus carota subsp. carota L., or wild carrot. We assayed heteroplasmy in both organellar genomes of 525 wild carrot individuals, grown from seed collected from five locations each of the native, naturalized, and invasive ranges of wild carrot. Plants were grown in greenhouse conditions at the University of Memphis in Memphis, TN, from September 2015 to November 2018, and fitness characteristics, including growth rates, number of leaves at bolting, total number of umbels, and pollen viability, were recorded. We present data on the occurrence and levels of mitochondrial and plastid heteroplasmy and overall phenotypic differentiation and fitness characteristics by geographic region of origin. Finally, we analyze these measures in terms of the presence/absence and levels of heteroplasmy within each of the mitochondrial and plastid genomes and determine if heteroplasmy of both organellar genomes together are correlated with fitness characteristics.


1 - University Of Memphis, Biological Sciences, 239 Ellington Hall, 3700 Walker Avenue, Memphis, TN, 38152, United States
2 - University Of Memphis, Biological Sciences, 3744 Walker Ave, 339 Ellington Hall, Memphis, TN, 38152, United States

Keywords:
heteroplasmy
paternal leakage
cytonuclear interactions
fitness.

Presentation Type: Oral Paper
Number: 0009
Abstract ID:1007
Candidate for Awards:Margaret Menzel Award


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