German scientists find method to predict and increase biomass yield of energy crops

Scientists from the Max-Planck Institut für molekulare Pflanzenphysiologie and the University of Potsdam have discovered [*.pdf/German] important clues for the development of a new plant breeding method that could revolutionise the creation of energy crops that produce high amounts of biomass. The energy contained in this plant matter can be converted into useable liquid, gaseous and solid biofuels.

Traditional plant breeding methods consist of cumbersome process of deliberate interbreeding of closely or distantly related species to produce new crops with desirable properties. Plants are crossbred to introduce traits and genes from one species into a new genetic background. The result is analysed after the new plant type has been grown and if unsatisfactory, the process begins all over again.

By looking at the fundamental growth processes of Arabidopsis thaliana and by identifying the chemical building blocks ('metabolites', see diagram) and their interaction, which drive its growth mechanism, the plant biologists from Germany found clues that make it possible to predict at an early stage which plant will yield most biomass later on. The method, called 'metabolic profiling', offers vast posibilities for the development of a new plant breeding paradigm.

The scientists think the concept of metabolic profiling can be applied to most plants, and will allow researchers to select the most promising ones in an early stage. Since the method makes it possible to predict the sheer biomass productivity of plants, it is especially important for selecting energy crops, where biomass productivity matters most:

"It is in this field that the concept will yield its most immediate results. This method will revolutionize the selection and breeding of dedicated energy crops, that can be used for biomass production." - Rhonda Meyer, Max-Planck Institute for Molecular Plant Physiology

The researchers published their findings in the March 13 issue of the Proceedings of the National Academy of Sciences. It is an open access article.

The method
Through photosynthesis, plants convert sunlight into the production of organic compounds they use to grow. The increase in biomass in plants depends on a multitude of environmental factors (sunlight, the availability of water and nutrients, pests, and so on) and on the plant's capacity to use its biochemical processes and its own internal 'energy reserves' in an optimal manner to bridge periods of environmental stress. This results in a very strict and rigid economy of resources that characterises a plant's metabolism:
bioenergy :: biofuels :: energy :: sustainability :: plant breeding :: metabolism :: yields :: biomass :: energy crops ::

But until now, it was unclear which set of factors and which metabolites precisely determine the growth mechanism of plants. The Max Plack researchers tackled the question by analysing a line of Arabidopsis thaliana (image, click to enlarge), the genetic profile of which is well known. Plant biologists already knew that an important carbohydrate like glucose gives out signals to increase growth and continue cell division. Looking further, the scientists used gaschromatography on the individual parts of the plant, and mass-spectrometry on its invidual chemical substances, such as sugars, acids and proteins.

They then isolated the substances which could be analysed in 85% of the samples. Finally, these selected chemical building blocks were then correlated to the biomass yields of the different samples in the Arabidopsis line. Rhonda Meyer, lead author of the article, says the correlation was so strong that it has now become possible to develop the method that accurately predicts the biomass growth potential of a series of plants, merely by looking at the composition, the amount and ratio of its chemical building blocks.

Image: In crossing different lines of Arabidopsis thaliana researchers observe diferences in biomass yields. The new, crossed generation of plants (upper line) are bigger than their parents (lower line). Using the results from this 'recombinant inbred line' and matching them with the metabolic analysis, it becomes possible to predict the biomass yield of the next generation of crossed plants. Courtesy: Max-Planck Institut für molekulare Pflanzenphysiologie

Diagram: Representation of the most important metabolites known by structure according to CCA on biochemical pathways. This representation of metabolism indicates all known metabolites we analyzed by using GC/MS that could be annotated in MapMan (28). Red color visualizes metabolites which are high ranked in CCA (positions 1–44), with ranking according to the color-coded scale bar.

More information:
Max-Planck Institut fur molekulare Pflanzenphysiologie: Wege aus der Energiekrise: Pflanzen mit mehr Biomasse. Max-Planck-Forscher und ihre Kollegen von der Universität Potsdam finden Hinweise auf eine Methode zur effektiveren Züchtung von "Energiepflanzen" [*.pdf] - March 8, 2007.

Rhonda C. Meyer, Matthias Steinfath, Jan Lisec, Martina Becher, Hanna Witucka-Wall, Ottó Törjék, Oliver Fiehn, Änne Eckhardt, Lothar Willmitzer, Joachim Selbig, Thomas Altmann, "The metabolic signature related to high plant growth rate in Arabidospsis thaliana" [*abstract or full article], PNAS, 5. März 2007