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06-2022

New insights into the effect of membrane proteins on plant growth

Scientists have uncovered two enzymes that control protein degradation of proteins in plant cell membranes, and established their role in plant growth and development.

Ubiquitin is a small regulatory protein found in most cells of eukaryotic organisms. It is important for altering the function of other proteins, and is most notably involved in protein degradation and protein localization within the cell. Ubiquitin regulates these functions by binding to and dissociating from target proteins, a process known as ubiquitination.

Scientists in Japan, Belgium and the United States, led by Associate Professor Takeo Sato at Hokkaido University, have discovered the first examples of destroying enzymes in plants that act on proteins in a cell’s cell membrane. Their findings published in the journal EMBO reportDescribe the functions of these proteins.

The addition of ubiquitin to target proteins is catalyzed by enzymes called ubiquitin ligases, and the reverse process, the removal of ubiquitin from the target protein, is catalyzed by deubiquitinating enzymes (DUBs). It was not known which plant DUBs were able to remove ubiquitin directly from membrane proteins. This lack of knowledge meant that the regulation of membrane protein stability was not fully understood.

The team demonstrated that two of these Arabidopsis thaliana The DUBs, UBP12 and UBP13, directly target the cell membrane-localized plant hormone receptor called BRI1.

BRI1 is important for the detection of brassinosteroids (BRs), steroidal phytohormones that are essential for growth and development. Typically, when BRI1 detects BR, it triggers a pathway that regulates gene expression in the nucleus. The abundance of cellular BRI1 is important for fine-tuning the BR signal, although the regulatory mechanism for how BRI1 abundance is optimized (fine-regulated) in cells was unclear. The scientists demonstrated that UBP12 and UBP13 ubiquitinated and stabilized BRI1.

In his experiments, he showed that Arabidopsis thaliana Plants that lacked the ability to express UBP12 and UBP13 were severely stunted and markedly less sensitive to BRs. When a mutant BRI1 – which could not be ubiquitinated – was introduced into these UBP12 and UBP13 deficient plants, the growth defects were partially restored. Notably, UBP12 and UBP13 target and act on the ubiquitinated BRI1.

The study showed that UBP12 and UBP13 are key regulators of plant growth through their interactions with BRI1. The study also provided insight into how membrane protein stability is maintained; However, more research is needed to fully understand the dynamics of BRI1 within the cell. In conclusion, the findings provide evidence that the role of plant DUBs is similar to that of mammalian DUBs.

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material provided by Hokkaido University, Note: Content can be edited for style and length.

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