Navigation Links
At long last, scientists figure out how plants grow

It has been one of the great mysteries in plant science.

Scientists have known since 1885 that the plant growth hormone auxin exists. They've known of its dramatic effects on plant growth and development since the 1930s. But only now do scientists know how it works.

In this week's Nature, Indiana University Bloomington biologists Mark Estelle, Nihal Dharmasiri and Sunethra Dharmasiri identify TIR1 as the protein that, with auxin, influences how and when plant cells grow and divide. In the same issue, scientists in the United Kingdom report a virtually identical result.

"How auxin works has been a holy grail in plant science," said Estelle, who led the research. "This was something even Charles Darwin considered, if only in spirit. That we've all been trying to figure it out for so long makes this latest discovery very satisfying."

Estelle said the finding is important for basic plant science, but may also lead to new insight into how related proteins function in animals, including humans.

In a 2001 report (also in Nature), Estelle and colleagues showed that the protein TIR1 acts to increase the expression of certain growth-related genes.

The scientists had not known at the time that TIR1 interacts directly with auxin (also known as indoleacetic acid, or IAA). With that finding, the scientists can now envision a complete life history for the growth hormone. Auxin is produced in the tips of plant shoots and branches. The hormone travels downward toward the roots. It migrates into plant cell nuclei, where it is picked up by the TIR1 portion of a four-protein complex called SCF(TIR1). SCF(TIR1) and auxin binds to yet another protein that represses the expression of a particular set of genes. And it's this complex of auxin, SCF(TIR1) and the repressor that signals enzymes to destroy the repressor, thereby turning on the repressed gene.

"The key interaction is between TIR1 and the repressor," Estelle said. "Nihal was able to get that to work in a test tube, but the interaction would only occur if he added auxin to the solution."

Auxin may stick around awhile, but it is eventually broken down by natural cell processes.

The scientists used the common plant model Arabidopsis thaliana (wall cress) for their experiments. They also expressed TIR1 in insect cell cultures, to make sure that the binding of TIR1 to auxin is not directly influenced by other plant cell proteins.

Auxins influence a wide variety of plant processes. For example, they are the hormones that cause roots to grow downward and flowers to track the moving sun. Auxins also stop the growth of lateral branches. Since auxins are produced in shoot tips, lopping off the tip can cause numerous side shoots to appear, giving a plant a denser, more sculpted look.

Auxin also promotes fruit development. In strawberries, for example, auxin produced by the developing seeds promotes the growth of a red and juicy fruit.

Another protein called ABP1 (Auxin Binding Protein 1) has previously been shown to bind auxin. But unlike TIR1 and auxin, it remains unclear whether the pairing of ABP1 and auxin actually stimulates plant growth.

The research reported by Estelle, Dharmasiri and Dharmasiri was funded by grants from the National Science Foundation, the National Institutes of Health and the U.S. Department of Energy.

To speak with Estelle, please call 812-856-1216 or e-mail him at

"The F-box protein TIR1 is an auxin receptor," Nature, v. 435, no. 7040


Source:Indiana University

Related biology news :

1. Wisconsin scientists grow critical nerve cells
2. UCSB scientists probe sea floor venting to gain understanding of early life on Earth
3. UAB scientists discover the origin of a mysterious physical force
4. Fox Chase Cancer Center scientists identify immune-system mutation
5. Weizmann Institute scientists develop a new approach for directing treatment to metastasized prostate cancer in the bones.
6. U-M scientists find genes that control growth of common skin cancer
7. UCLA scientists transform HIV into cancer-seeking missile
8. RNA project to create language for scientists worldwide
9. Carnegie Mellon scientists develop tool that uses MRI to visualize gene expression in living animals
10. To control germs, scientists deploy tiny agents provocateurs
11. Leprosy microbes lead scientists to immune discovery
Post Your Comments:

(Date:5/16/2016)... 2016   EyeLock LLC , a market leader ... of an IoT Center of Excellence in ... development of embedded iris biometric applications. EyeLock,s ... and security with unmatched biometric accuracy, making it the ... DNA. EyeLock,s platform uses video technology to deliver a ...
(Date:5/9/2016)... , UAE, May 9, 2016 ... when it comes to expanding freedom for high net ... Even in today,s globally connected world, there is ... conferencing system could ever duplicate sealing your deal with ... obtaining second passports by taking advantage of citizenship via ...
(Date:4/28/2016)... BANGALORE, India , April 28, 2016 /PRNewswire/ ... product subsidiary of Infosys (NYSE: INFY ), and ... global partnership that will provide end customers with ... banking and payment services.      (Logo: ... area for financial services, but it also plays a fundamental ...
Breaking Biology News(10 mins):
(Date:6/27/2016)...  Liquid Biotech USA , ... Sponsored Research Agreement with The University of Pennsylvania ... cancer patients.  The funding will be used to ... clinical outcomes in cancer patients undergoing a variety ... employed to support the design of a therapeutic, ...
(Date:6/24/2016)... ... June 24, 2016 , ... While the majority of commercial ... Cary 5000 and the 6000i models are higher end machines that use the more ... the spectrophotometer’s light beam from the bottom of the cuvette holder. , FireflySci ...
(Date:6/23/2016)... CAMBRIDGE, Mass. , June 23, 2016 /PRNewswire/ ... the development of novel compounds designed to target ... compound, napabucasin, has been granted Orphan Drug Designation ... in the treatment of gastric cancer, including gastroesophageal ... cancer stemness inhibitor designed to inhibit cancer stemness ...
(Date:6/23/2016)... ... June 23, 2016 , ... ... (Yeast and Mold) microbial test has received AOAC Research Institute approval 061601. , ... tests introduced last year,” stated Bob Salter, Vice President of Regulatory and Industrial ...
Breaking Biology Technology: