New insights into the effects of membrane proteins on plant growth

EMBO Reports (2022). DOI: 10.15252/embr.202153354″ width=”683″ height=”530″/>

Compared to a wild-type Arabidopsis (WT, left), plants lacking either UBP12 and UBP13 (#1-7 and #12-8, center) or BRI1 (bri1-null, right) exhibit extreme growth retardation. Credit: EMBO Reports (2022). DOI: 10.15252/embr.202153354

Scientists have unveiled two enzymes that regulate protein breakdown of proteins in plant cell membranes and established the role they play in plant growth and development.

Ubiquitin is a small regulatory protein found in most cells of eukaryotic organisms. It is vital for altering the function of other proteins and is particularly involved in protein degradation and protein localization in the cell. Ubiquitin regulates these functions by attaching to and detaching from the target proteina process called ubiquitination.

Scientists from Japan, Belgium and the US, led by associate professor Takeo Sato of Hokkaido University, have discovered the first examples of deubiquitinating enzymes in plants that act on proteins in the cell membrane of the cell. Their findings, published in the journal EMBO Reportsdetail the function of these proteins.

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

Nieuwe inzichten in effecten van membraaneiwitten op plantengroei

In normal cells (left), BRI1 (fluorescent yellow) is mainly present in the cell membrane and part of BRI1 is degraded in the vacuoles. In cells lacking UBP12 and UBP13, the BRI1 concentration in vacuoles is greatly increased as a large part is degraded. Credit: EMBO Reports (2022). DOI: 10.15252/embr.202153354

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

BRI1 is vital for the detection of brassinosteroids (BRs), steroidal phytohormones essential for growth and development. When BRI1 detects BR, it usually activates a pathway that regulates gene expression in the core. The abundance of cellular BRI1 is crucial to precisely mediate the BR signal, although the regulatory mechanism: for how BRI1 abundance in the cells is optimized (refined) was unclear. The scientists showed that UBP12 and UBP13 de-ubiquitinated and stabilized BRI1.

In their experiments, they showed that Arabidopsis thaliana plants lacking the ability to express UBP12 and UBP13 were severe in growth and markedly less sensitive to BRs. When a mutant BRI1 – which failed to become ubiquitous – was introduced into these UBP12- and UBP13-deficient plants, growth defects were partially repaired. In particular, UBP12 and UBP13 target and act on ubiquitous BRI1.

The study showed that UBP12 and UBP13 are the main regulators of: plant growth through their interaction with BRI1. The study also provided insight into how the stability of membrane proteins is preserved; however, further research is needed to fully understand the dynamics of BRI1 in the cell. Finally, the findings provide evidence that plant DUBs have roles similar to those of mammalian DUBs.

Researchers reveal function of plant E3 ubiquitin ligase and deubiquitinase pair in regulating abscisic acid perception

More information:
Yongming Luo et al, Deubiquitinating enzymes UBP12 and UBP13 stabilize the brassinosteroid receptor BRI1, EMBO Reports (2022). DOI: 10.15252/embr.202153354

Quote: New insights into effects of membrane proteins on plant growth (2022, June 3) retrieved June 3, 2022 from

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