Abstract Detail

Molecular Ecology

Senden, Esther [1], Joachim, Surm [2], Yamit, Bar-Lev [1], Sapir, Yuval [3].

The molecular basis of continuous flower colour variation in Oncocyclus irises.

Flower colour is considered to be an adaptive trait enabling the plant to interact with its environment, resulting in a dazzling variety of flower colours. While the mechanisms that create and maintain discrete colour variation among populations have been well studied, less attention has been paid to cases where colour variation is maintained within populations. Even more rare is within-population colour variation on a continuous scale. Questions concerning the biochemical and genetic basis that give rise to this particular colour variation and how this variation is maintained over time remain unanswered. Anthocyanins are the main pigment compounds responsible for flower colour variation and the genes underlying its biochemical pathway, the Anthocyanin Biosynthesis Pathway (ABP), are widely studied. Flower colour variation is usually driven by simple changes in the ABP genes controlling pigment synthesis. However, their evolutionary trajectory and the effect on the biochemistry of these pigments leading to continuous colour variation are poorly understood.
Here we study the Middle-Eastern populations of Oncocyclus irises. This group is unique in exhibiting flower colour variation on a continuous scale. We aim to understand how ABP gene expression influences pigment synthesis resulting in the continuous range of flower colours in these irises. Finally, to understand whether flower colour is under selection, we measure colour-associated fitness in natural populations over multiple years.
We found differential anthocyanin pigment composition, rather than differences in pigment concentration, to be important for the colour variation observed in these irises. These findings are supported by the expression patterns of two genes sitting at the ABP branchpoints, F3’H and F3’5’H, determining final pigment composition. There seems to be a slight fitness advantage towards darker pigmented flowers but no significant fitness effect was detected.
To our knowledge this is the first study exploring the evolution and maintenance of continuous flower colour variation in a non-model species, thereby taking into account the full path of natural selection on flower colour, from genotype to phenotype to fitness. Flower colour sits at the intersection of ecological interactions, genetics and evolution, and thus provides an excellent system to understand the causes of variation, and more importantly, what maintains or erodes it

1 - Botanic Garden Tel Aviv University, Haim Levanon 55, Tel Aviv, Israel, 6997801, Israel
2 - The Hebrew University of Jerusalem, Department of Ecology, Evolution and Behavior, Jerusalem 91904, Israel
3 - Tel Aviv University, Ramat Aviv, Tel Aviv, TA, 69978, Israel

Keywords:
Floral colour
anthocyanins
floral evolution
gene expression.

Presentation Type: Oral Paper
Session: ME1, Molecular Ecology
Location: /
Date: Tuesday, July 20th, 2021
Time: 4:15 PM(EDT)
Number: ME1006
Abstract ID:1121
Candidate for Awards:None