4 August 2016

MicroProteins act as on/off switches for flowering control in plants


A certain plant protein recognized for decades as an accelerator for plant flowering can be transformed into a brake, when it interacts with two newly identified microProteins. The findings from Copenhagen Plant Science Centre bring perspective into the agricultural industry, as microProteins are potential versatile tools for controlling the bloom of many crop plants.

By Natasja Lykke Corfixen

Late flowering transgenic plants with elevated microProtein levels (the three plants on the right) compared to a wild type (far left). Photo: Graeff et al. (2016), PLOS Genetics.

The flowering of plants is a light and day-length dependent process, which genetically has been studied for over 100 years. Specific day lengths trigger molecular signals in plant leaves, which are responsible for the formation of flowers. But recent research made at the Copenhagen Plant Science Centre and published in PLOS Genetics shows that two microProteins physically interact with one of the molecular regulators of this process, thereby slowing down flowering.

MicroProteins are small proteins found in both plants and animals, which function by binding to and affecting larger proteins. Many of these microProteins have been identified before, but the project leader and Associate Professor Stephan Wenkel explains the identification of these two particular proteins:

Stephan Wenkel and his research group. Photo: Copenhagen Plant Science Centre.

“Back when I was a group leader in Germany, we developed computer programs to identify proteins that were small and related to larger proteins based on their sequence. Among the many things we found were these two small proteins that are closely related to one of the important regulating proteins of plant flowering, the CONSTANS transcription factor.” 

After identifying a large number of microProteins these two were selected for further investigation and Stephan Wenkel adds:

“We studied their function and found that they can interact with the CONSTANS transcription factor and because CONSTANS activity is required for the flowering response these small proteins can delay the flowering process.”

The microProteins are assisted by a third protein
Unlike proteins with similar functions, microProteins are characterized by containing only one functional domain. But the study determined that a second area of the microProteins enables them to form complexes with a third protein:

“What we found is that it is not only the interaction between these microProteins and the CONSTANS protein that strongly represses flowering, it is the interaction with a specific third protein, called TOPLESS, which seems to be required for the function of the microProteins.”

Stephan Wenkel points out that this brings up additional questions on how to differentiate this binding site from a possible second functional domain of the microProtein.

The potential of microProteins used as brake pedals
“So why do we not just knock out the genes for transcription factors such as CONSTANS to delay flowering? With microProteins you can potentially have effects that are more specific or milder compared to mutations that would knock out the gene,” Stephan Wenkel adds.

He also thinks that future aspects of the research could include investigations of how to induce these microProteins naturally to potentially control the flowering of plants:

“These microProteins function a little bit like a brake pedal in a car: You can press the brake and then it slows down the flowering process or you can remove the entire brake pedal and see whether you can drive faster.”

As microProteins can be found in many organisms, this and further research can be applied in many fields, but for now recent research has been focusing on the microProteins of plants. The model organism of this research Arabidopsis contains the same molecular mechanisms as many crop plants and microProteins may therefore have future potential within agriculture to regulate flowering and thereby controlling the timing of ripening and harvest.