Insight into plant behavior could aid quest for efficient biofuels

Posted by Biomechanism 

Tiny seawater alga could hold the key to crops as a source of fuel and plants that can adapt to changing climates.

Researchers at the University of Edinburgh have found that the tiny organism has developed coping mechanisms for when its main food source is in short supply.

Understanding these processes will help scientists develop crops that can survive when nutrients are scarce and to grow high-yield plants for use as biofuels.

Green algae in seawater floating on the water surface in a creek. Credit: Biomechanism.com

The alga normally feeds by ingesting nitrogen from surrounding seawater but, when levels are low, it reduces its intake and instead absorbs other nutrients, such as carbon and phosphorus, from the water. The organism is also able to recycle nitrogen from its own body, breaking down proteins that are plentiful to make other proteins that it needs to survive.

Nitrogen is needed by all plants to survive but the alga’s survival strategies vary from most other plants which, when nitrogen is scarce, tend to widen their search for it.

Like many organisms, the alga – Ostreococcus tauri – is also driven by daylight and its body clock – for example, proteins that produce starch for food are active in the evening, after the plant has photosynthesised sugars from sunlight in the day.

The study, in the Journal of Proteomics, was funded by the Biotechnology and Biological Sciences Research Council and the Engineering and Physical Sciences Research Council.

Dr Sarah Martin, of the University of Edinburgh, who took part in the study, said: “This tiny alga certainly punches above its weight when it comes to survival. Our study has revealed some curious ways in which the organism finds the nutrients it needs to stay alive – tricks like these could be useful to us in developing sustainable crops for the future.”

More Information On Ostreococcus

Ostreococcus tauri strain OTH95, photo courtesy of Hervé Moreau, Laboratoire Arago

Ostreococcus belongs to the Prasinophyceae, an early-diverging class within the green plant lineage, and is reported as a globally abundant, single-celled alga thriving in the upper (illuminated) water column of the oceans. The most striking feature ofO. tauri and related species is their minimal cellular organization: a naked, nearly 1-micron cell, lacking flagella, with a single chloroplast and mitochondrion.

Three different ecotypes or potential species have been defined, based on their adaptation to light intensity. One (O. lucimarinus) is adapted to high light intensities and corresponds to surface-isolated strains. The second (RCC141) has been defined as low-light and includes strains from deeper in the water column. The third (O.tauri) corresponds to strains isolated from a coastal lagoon and can be considered light-polyvalent. Comparative analysis of Ostreococcus sp will help to understand niche differentiation in unicellular eukaryotes and evolution of genome size in eukaryotes.

According to Bioinformatics & Evolutionary Genomics in Belgium. Ostreococcus tauri is a unicellular green alga that was discovered in the Mediterranean Thau lagoon (France) in 1994. With a size less than 1 µm , comparable with the size of a bacterium, it is the smallest eukaryotic organism described until now.

Its cellular organisation is rather simple with a relative large nucleus with only one nuclear pore, a single chloroplast, one mitochondrion, one Golgi body and a very reduced cytoplasmatic compartment. The presence of only one chloroplast and mitochondrium makes it interesting to use not only for evolutionary studies, but also for experimental studies. Morphologically, the absence of flagella is the most typical characteristic of Ostreococcus tauri compared with other green algae.

Apart from this simple cellular structure, the genome size ofOstreococcus tauri is the smallest of all known eukaryotes. The nuclear genome is about 12 Mb, fragmented into 20 chromosomes, ranging in size from 120 to 1500 Kb. Phylogenetic analysis placed Ostreococcus tauri within the Prasinophyceae, an early branch of the Chlorophyta (green algae).