Yellow vs purple
Often the flowers of one species are equal in colour. But sometimes not. Like a Tibetan Iris which can have either yellow or purple flowers. Now Chinese researchers show in BMC Plant biology that this is caused by mistakes in the colour gene F3H
Plants depend on the colour of their flowers. They use it to attract their favourite pollinators. When these stay away, plants have a big problem: they can’t procreate. To investigate the influence of flower colour in more detail the researchers analysed the Tibetan Iris.
The first thing the researchers studied was the ratio of pollen vs ovules. This can tell something about the success of flowers to attract pollinators. But in this case the researchers did not see a clear difference. The number of pollen in purple or yellow flowers did not vary. However, the yellow flowers had more ovules. But not enough to say that the ratio between pollen and ovules differ between yellow and purple flowers.
Yellow flowers can’t no longer make the purple pigment
Subsequently the researchers analysed why the flowers had different colours. For this the researchers analysed the pigments present in the flowers. Not surprising the purple flowers had more anthocyanins than the yellow flowers. Further analysis indicated that the most likely reason for this was a difference in expression of the anthocyanin producing gen F3H.
Closer study showed that in irises with yellow flowers this gene is full of mutations. Mutations that make the gene non-readable by the plant. With as result that the plant is not making any F3H protein. Without this protein the plant can’t make anthocyanin. And without anthocyanin no purple flowers.
As this shows, even without clear preference of pollinators for either yellow or purple flowers, in the long run yellow flowers still dominate over purple ones. Simply because they can’t no longer make the purple pigment.
Literature
Zhou, ZL., Wang, GY., Wang, XL. et al. Flower color polymorphism of a wild Iris on the Qinghai-Tibet plateau. BMC Plant Biol 23, 633 (2023). https://doi.org/10.1186/s12870-023-04642-9
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