How steroid hormones enable plants to grow

Aug 19, 2014
The photo shows just how important brassinosteroids are for the development of plants. A deficit of the plant hormone has disrupted growth in the cucumber plant on the right. Credit: Wilfried Rozhon / TUM

Plants can adapt extremely quickly to changes in their environment. Hormones, chemical messengers that are activated in direct response to light and temperature stimuli help them achieve this. Plant steroid hormones similar to human sex hormones play a key role here. In the current edition of Nature Communications, scientists describe a new signaling mode for the brassinosteroid class of hormones.

Plants are superior to humans and animals in a number of ways. They have an impressive ability to regenerate, which enables them to regrow entire organs. After being struck by lightning, for example, a tree can grow back its entire crown. But there is one major downside to life as a plant: They are quite literally rooted to the habitats in which they live and therefore completely at the mercy of the elements. In response to this dilemma, plants have developed mechanisms that enable them to rapidly adapt their growth and development to changes.

Plant hormones are important enablers of this flexibility. Brassinosteroids play a key role here. These hormones have an effect at the lowest concentrations; they regulate cell elongation and division and are active throughout the entire lifecycle of a plant. A team of researchers from Technische Universität München (TUM) and the University of Vienna have now mapped a new signaling mode for brassinosteroids.

Meeting points for DNA-binding protein

When brassinosteroids bind to a receptor on a cell wall, they trigger a multi-level cascade of reactions that regulates the activity of the CESTA (CES) transcription factor. Transcription factors bind to the DNA in a cell's nucleus and are capable of activating genes that change the protein composition in the cell.

A team of scientists – headed by Prof. Brigitte Poppenberger at TUM's Institute of Biotechnology of Horticultural Crops – has been able to show for the first time that the concentration of CES protein increases in certain nuclear regions following brassinosteroid activation.

These structures occur as nuclear bodies in the cell nucleus. The scientists believe that the CES transcription factor collects in specific regions of the DNA in order to effectively control gene function. "The cell seems to bundle key resources to rapidly trigger the production of certain proteins. We can compare this to a construction site, for example, where workers temporarily gather at a certain location to unload building material," explains Poppenberger.

Brassinosteroids are growth hormones found in all plants. The steroid hormones were first isolated in rapeseed (Brassica napus) in 1979 and were subsequently named after this plant. Credit: A. Heddergott / TUM

New signal pathway

The scientists also mapped the mechanism that gives the CES molecules the signal to gather. The molecules have a binding site for SUMO protein. As soon as this attaches, CES moves to . While this is happening, it is protected from being broken down by enzymes. "What is interesting here is that the SUMO marker seems to strengthen the effect of CES," continues Poppenberger. "This is the opposite of what happens in the animal world, where the SUMO protein is known to repress effects conferred by ."

The research findings are an important step towards understanding more about the functions of brassinosteroids. "We have been using other kinds of hormones to promote growth and increase crop yields in horticulture and agriculture for decades now," says Poppenberger. "But we have never leveraged the potential of brassinosteroids. Understanding how they work will help us utilize them for plant production. This is what we are aiming for in our work."

Explore further: To grow or to defend: How plants decide

More information: Interplay between phosphorylation and SUMOylation events determines CESTA protein fate in brassinosteroid signaling; Mamoona Khan, Wilfried Rozhon, Simon Josef Unterholzner, Tingting Chen, Marina Eremina, Bernhard Wurzinger, Andreas Bachmair, Markus Teige, Tobias Sieberer, Erika Isono, and Brigitte Poppenberger, Nature Communications; DOI: 10.1038/ncomms5687

add to favorites email to friend print save as pdf

Related Stories

Nailing down a crucial plant signaling system

Jan 23, 2011

Plant biologists have discovered the last major element of the series of chemical signals that one class of plant hormones, called brassinosteroids, send from a protein on the surface of a plant cell to the cell's nucleus. ...

Mastermind steroid found in plants

Nov 15, 2010

Scientists have known for some time how important plant steroids called brassinosteroids are for regulating plant growth and development. But until now, they did not know how extensive their reach is. Now researchers, including ...

Steroids control gas exchange in plants

Feb 05, 2012

Plants leaves are sealed with a gas-tight wax layer to prevent water loss. Plants breathe through microscopic pores called stomata (Greek for mouths) on the surfaces of leaves. Over 40% of the carbon dioxide, CO2, in the ...

Recommended for you

Research sheds light on what causes cells to divide

Dec 24, 2014

When a rapidly-growing cell divides into two smaller cells, what triggers the split? Is it the size the growing cell eventually reaches? Or is the real trigger the time period over which the cell keeps growing ...

Locking mechanism found for 'scissors' that cut DNA

Dec 24, 2014

Researchers at Johns Hopkins have discovered what keeps an enzyme from becoming overzealous in its clipping of DNA. Since controlled clipping is required for the production of specialized immune system proteins, ...

Scrapie could breach the species barrier

Dec 24, 2014

INRA scientists have shown for the first time that the pathogens responsible for scrapie in small ruminants (prions) have the potential to convert the human prion protein from a healthy state to a pathological ...

Extracting bioactive compounds from marine microalgae

Dec 24, 2014

Microalgae can produce high value health compounds like omega-3s , traditionally sourced from fish. With declining fish stocks, an alternative source is imperative. Published in the Pertanika Journal of Tr ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.