Fluctuating genes
There is a lot more noise than assumed in gene expression. Nevertheless, organisms still manage to develop complex organs. As American researchers show in Nature Communications.
When we think about gene expression, we assume that genes are activated at set locations for doing their job. And that when this is not the case things are spinning out of control. But at the same time researchers also see a lot of noise in gene expression. Think about FLC, the gene that prevents flower development, that is slowly turned off during winter. But it is not that all cells at the same time gradually produce less FLC, but that in more and more cells FLC is completely turned off.
In the new study researchers looked at how this works for genes that are regulated by the hormone auxin. Firstly, the researchers studied the expression of an auxin reporter gene. In young flower growth centres, the location where the reporter was turned on fluctuated. As if the reporter was still searching for its spot. In older flower growth centres, with more cells, the fluctuations were restricted to the four locations of the future sepals.
To be sure that they measured fluctuations of gene expression of the auxin reporter, and not of auxin itself, the researchers flooded the flower growth centres with auxin. But even with auxin present in all cells, the expression of the auxin reporter kept fluctuating.
The fluctuations are especially noticeable when there are only a handful of cells
Now, you can say, the auxin reporter fluctuates, but that is artificial, what about the actual genes. To find out the researchers fused the promoters of two auxin regulated genes each with two fluorescent proteins. In this way the researchers could see if the gene expression fluctuated not only by location, but also within the cell itself. As without noise the cell would produce equal amounts of each of the two fluorescent proteins.
But that is not what the researchers observed. Not only did the researchers see different locations light up than for the auxin reporter. But they noticed also fluctuations in the amounts of fluorescent protein. The through the plant regulated genes therefore also fluctuate. Although, this fluctuation was less than that was observed for the auxin reporter.
The fluctuations are especially noticeable when there are only a handful of cells. The more cells there are the less fluctuation there is. In addition, there are other dampening effects that prevent genes to fluctuate too much. But how the plant still manages with all that noise to form a similar forms time after time, that is something that the researchers don’t know yet.
Literature
Kong, S., Rusnak, B., Zhu, M. et al. Stochastic gene expression in auxin signaling in the floral meristem of Arabidopsis thaliana. Nat Commun 16, 4682 (2025). https://doi.org/10.1038/s41467-025-59943-4
Plant en Zo 