Plant & zo
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How to do both
Sometimes there are things by which you think; how? So are there for example gen-on switches in plants that turns on a gene when there are only few of them but turn off the same gene when they are with many. Contradictory you would say. The logical expectation would be that the more gen-on switchers there are the more, let’s say the brighter, the gen is turned on. One of these contradictory gene-on switches is WUS, and researchers have long wondered how WUS is managing this.
WUS works in the growth region of the stem. And is needed to keep the cells of the growth region from specializing. Only in this way can the growth region keeps delivering new cells for leave and stem growth. To prevent WUS doing its job to enthusiastically CLV3 is reducing the amount of WUS. WUS in turn is turn works to increase the amount of CLV3. In this way they keep each other, and the growth region in balance.
The amount of CLV3 is not only dependent on the amount of WUS, but also on the CLV3-gene activation-regions
But in large amounts WUS is actually turning off the CLV3-gene. American researchers now found out how WUS does this, this stimulating as well as slowing down CLV3 production. The key was in the DNA, in the so-called activation-regions that are laying in front of the CLV3-gene. CLV3 has five of those. When WUS binds one of these activation-regions then it is turning on the CLV3-gene. Binds a second WUS to the first WUS, then it the CLV3-gene is turned off again.
WUS, the researchers noted, does not bind for long. At low concentrations, a second WUS does not get a chance to bind to the first WUS, as it has left the activation-region already. Only when there is a large amount of WUS, then a second WUS can bind to the first. Only then WUS turns off the CLV3-gene.
This was not the whole story, the researchers discovered also that more WUS is needed to turn of the CLV3-gene when the activation-regions of the CLV3-gene are laying further apart. The activation-regions were working together. Therefore, the amount of CLV3 is not only dependent on the amount of WUS, but also on the CLV3-gene activation-regions. How many there are, how far apart they lay and how long the bind WUS. They all regulate the amount CLV3 available to keep WUS under control, and in turn the size of the growth region.
Literature
Kevin Rodriguez, Albert Do, Betul Senay-Aras, Mariano Perales, Mark Alber, Weitao Chen, G. Venugopala Reddy (2022) Concentration-dependent transcriptional switching through a collective action of cis-elements. Science Advances 8, eabo6157 DOI: 10.1126/sciadv.abo6157
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