Hybrids and Hybridization
McCarthy, Elizabeth , Berardi, Andrea , Lawhorn, Amber , Kurti, Amelda , Giovannoni, James , Smith, Stacey , LITT, AMY .
Floral color differences in Nicotiana allopolyploids: the genetic and biochemical basis.
Polyploidy has played an important role in the evolution of angiosperms. Allopolyploidy (polyploidy accompanied by interspecific hybridization) can result in genetic and epigenetic changes, transposable element activation, chromosomal rearrangements, and even transgressive phenotypes that fall outside the range found in the progenitors. Differences in floral phenotypes may attract different pollinators, which may facilitate allopolyploid establishment and reproductive isolation from its progenitors as well as subsequent species diversification following allopolyploidy. Here, we examine the genetic and biochemical basis of diverse and transgressive floral colors in Nicotiana (tobacco) allopolyploids. Nicotiana is an excellent system in which to study allopolyploidy because nearly half of its species are allotetraploids that arose at different points during the evolution of the genus. This age range, from synthetic allopolyploids made in the lab to natural allopolyploid species that range from 0.2 to 10 million years old, allows for investigation of both the immediate and long-term consequences of allopolyploidy and can provide insight into the progression of allopolyploid evolution over time. Nicotiana species display diversity in floral form and color, and many related allopolyploid species that share the same progenitors have divergent floral traits. Here, we investigate floral color differences among Nicotiana tabacum accessions as well as among synthetic lines that share the same progenitors as N. tabacum. We determine the underlying pigment composition of these floral colors and link them to differences in expression patterns of genes involved in the flavonoid biosynthetic pathway. The flavonoid biosynthetic pathway is a branched pathway that produces both brightly colored anthocyanins and colorless (to humans) flavonols, which are involved in determining floral color. Magenta N. tabacum flowers have increased cyanidin concentration, but lower flavonols than pale pink N. tabacum flowers. Synthetic lines also display differences in the intensity of pink coloration, and paler flowers have lower cyanidin concentration. The pale pink phenotype in both natural and synthetic accessions is correlated with a dramatic increase in the expression of the flavonoid biosynthetic genes that produce flavonols over the expression of those that generate anthocyanins. This suggests that competition between these enzymes for shared substrates may underlie differences in floral phenotype.
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1 - University of California, Riverside, Department of Botany and Plant Sciences, 900 University Ave., Riverside, CA, 92521, USA
2 - University of Bern, Institute of Plant Sciences, Altenbergrain 21, Bern, CH-3013, Switzerland
3 - Cornell University, USDA-ARS and Boyce Thompson Institute for Plant Research, Ithaca, NY, USA
4 - University Of Colorado-Boulder, School Of Biological Sciences, Campus Box 334, Boulder, CO, 80309-0334, USA
Presentation Type: Oral Paper
Candidate for Awards:None