Deciphering the working of a protein
Proteins are the workers of a cell. But how these workers do their job is often unknown. Still researchers can make educated guesses based on how a protein looks, and where and when it is present in a cell and organism. But to really get to know what a protein does there is no other option than to study its parts in detail. Work that keeps lots of researchers occupied. As it did the Dutch researchers that studied how SCZ works, a protein that is needed for the correct growth of roots.
Plants that do not have any SCZ do not have any growth centres in their roots. Moreover, their root cap is unorganised, they have an extra layer of cells, and their root hairs don’t grow from the cells on the outer layer of the root, but from a deeper layer within. Al together lots of things going wrong. The question is what is the job of SCZ?
To find this out, the researchers analysed which part of SCZ is needed to rescue plants without any SCZ. In this regard, they made mutations in specific parts of the SCZ protein and inserted this protein into plants without SCZ. Studying the resulted plant showed that the DNA binding domain and the organizing domain where required for the rescue of plants without SCZ.
The DNA binding domain is giving SCZ its specificity
Based on these results and existing knowledge the researchers studied if SCZ is involved in either repressing or promoting the reading of genes. They did this by adding the active part of a known gene promotor or gene repressor to SCZ. Subsequently the researchers analysed which of these SCZ forms could rescue the roots of plants that did not have any SCZ. This occurred for the gene repressing addition, but not for the gene promoting addition. Suggesting that SCZ is a gene repressor.
Lastly the researchers studied which part of the SCZ protein is needed for specific gene-repression. This they did through swapping the DNA binding domain and organisation domain with those of a closely related protein. This showed that the DNA binding domain, not the organisation domain is giving SCZ its specificity.
Through the detailed studying of each part of SCZ the researchers discovered that SCZ is a gene repressor which is getting its specificity from its DNA binding domain. Now the next challenge is finding out which genes are repressed by SCZ.
Literature
Renan Pardal et al., (2023) SCHIZORIZA domain-function analysis identifies requirements for its specific role in cell fate segregation, Plant Physiology, kiad456, https://doi.org/10.1093/plphys/kiad456
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