Blushing flowers
Some flowers shift colour after pollination. In this way they signal to pollinators here is nothing more to get. Now Chinese and American researches discovered which gene is regulating this in Lotus species.
The flowers of Lotus japonicus and Lotus filicaulis are both yellow. Only one of those, L. filicaulis, colours a blushing orange-red after pollination. Steering the pollinators to the yellow not-pollinated flowers. Resulting in a higher pollination efficiency. But how the plants exactly regulate their colour change was still unknown.
To find out the researchers first studied which metabolites were involved. They found that both the yellow and the orange-red was coming from anthocyanins.
Gen activator PAP1 lets L. filicaulis blush after pollination
Subsequently the researchers studied the genes responsible for the production of anthocyanins. They noticed that after pollination some of the anthocyanin production genes that were turned on in L. filicaulis did not turn on in L. japonicus. In addition the researchers checked if the anthocyanin production genes of L. japonicus produced functional enzymes. Here they found no problems.
Because there was nothing wrong with the production of anthocyanin in L. japonicus, the researchers studied the gene that activate the anthocyanin production genes. One of these, PAP1, stood out. This gene was more activated after pollination. Not only in L. filicaulis but also in L. japonicus, although at a slightly lower intensity. It did not completely explain why the production of anthocyanins did not start after pollination in L. japonicus.
To be sure that they had the correct gene, the researchers turned PAP1 off in L. filicaulis. The flowers of PAP1 missing plants did not blush after pollination. Showing that PAP1 was indeed activating the anthocyanin production after pollination.
A mutation hinders the translation of the PAP1 gene in L. japonicus
Leaving the question of why the PAP1 gene was not doing its job in L. japonicus. To investigate this the researchers studied the nucleotide order of PAP1. Thereby the found two differences at the start of the gene. The first difference, a C versus a G, did not appear to do anything. The second difference, a T versus a G did. It was laying in the ATG start codon.
The AGG in L. japonicus means that the plant was not translating the gene correctly into its protein. This could have different reasons. It can be that the protein translation starts later, resulting in that the protein could not regulate other genes anymore. Or it could be, as the researchers suspect, that the gene is translated into its protein, but at verry inefficiently so.
Whatever the reason, in the end it means that less anthocyanin producing enzymes are working in L. japonicus. As a result L. japonicus cannot blush after pollination.
Literature
Gao, R., Li, Y., Shan, X., Wang, Y., Yang, S., Ma, S., Xia, Z., Zheng, H., Wei, C., Tong, L., Qin, J., Gao, X. and Cronk, Q. (2024), A single nucleotide polymorphism affects protein translation and leads to post-anthesis color change variation in closely related Lotus species. Plant J. https://doi.org/10.1111/tpj.17188
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