Protein plays role in helping plants see light

Oct 12, 2011

Plants do not have eyes or legs, yet they are able to "see" and move toward and away from light. This ability, called phototropism, is controlled by a series of molecular-level signals between proteins inside and between plant cells. In a paper published in The Plant Cell, University of Missouri scientists report for the first time the elusive role a critical protein plays in this molecular signaling pathway that regulates phototropism in plants.

Directional light that induces phototropism is sensed by a plant through the action of two light-sensing proteins, phototropin 1 and phototropin 2. These proteins act as and initiate the phototropic signaling response in conjunction with a third , called NPH3.

"If the phototropic were like a baseball game, the phototropins would be the pitcher and NPH3 the catcher who work together to coordinate the signal, or pitch," says Mannie Liscum, a professor of in the College of Arts and Science and in the Christopher S. Bond Life Sciences Center. "Prior to this study, no one knew how NPH3 and the phototropins cooperated to facilitate the signal."

Using a combination of genetic and biochemical methods, Liscum and colleagues found that NPH3 functions as part of a protein complex that modifies phototropin 1 by the addition of a small protein "tag" called ubiquitin. Either a single ubiquitin or a chain of ubiquitin proteins is added, depending on the amount of light the plant "sees."

If we continue the baseball analogy, ubiquitin is the hand signals NPH3 uses to coordinate with phototropin 1 the type and sequence of signals depending on the particular lighting situation.

"In low-light conditions, phototropin 1 is modified with single ubiquitin proteins and then apparently moves to a different part of the cell. In high-light conditions, phototropin 1 is modified with multiple ubiquitin proteins and is degraded by the cell to shut down further signaling," says Liscum.

The finding may have applicability to research beyond phototropism in plants.

"The tagging of proteins with ubiquitin represents a common biochemical event throughout the biological world. In fact, many human disease pathologies are associated with alterations in ubiquitin-tagging," says Liscum. "Our studies identifying a single enzyme complex that is capable of modifying a substrate in different ways simply based on the environmental conditions may therefore have implications on fields far askew from agriculture."

Explore further: How do our muscles work? Scientists reveal important new insights into muscle protein

Related Stories

A new signaling pathway of the immune system is elucidated

Mar 31, 2011

A new signaling pathway, which is important for the regulation of the immune response and inflammation, was discovered by an international team of scientists led by prof Ivan Dikic from the Goethe University, Frankfurt, Germany. ...

Researchers identify a scaffold regulating protein disposal

Dec 11, 2009

How does a cell manage to identify and degrade the diverse types of defective proteins and thus protect the body against serious diseases? The researchers Sabine C. Horn, Professor Thomas Sommer, Professor Udo Heinemann and ...

Recommended for you

How calcium regulates mitochondrial carrier proteins

18 hours ago

Mitochondrial carriers are a family of proteins that play the key role of transporting a chemically diverse range of molecules across the inner mitochondrial membrane. Mitochondrial aspartate/glutamate carriers are part of ...

Team conducts unprecedented analysis of microbial ecosystem

19 hours ago

An international team of scientists from the Translational Genomics Research Institute (TGen) and The Luxembourg Centre for Systems Biomedicine (LCSB) have completed a first-of-its-kind microbial analysis of a biological ...

Students create microbe to weaken superbug

Nov 25, 2014

A team of undergraduate students from the University of Waterloo have designed a synthetic organism that may one day help doctors treat MRSA, an antibiotic-resistant superbug.

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.