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What causes a particular alga to be crowned “the fastest growing plant cell in the world?” A new
study involving a Tel Aviv University researcher set out to track the photosynthetic properties of the
alga Chlorella ohadii, a type of green algae considered to be the fastest growing plant cell.

The study’s findings indicate that the main factors behind the plant’s rapid photosynthesis rate lie
in its efficient metabolic processes. The researchers found that this alga has a unique ability to elicit
a chemical reaction in which it is able to efficiently and quickly recycle one of the components used
by an enzyme called RuBisCO, in a manner that significantly speeds up the photosynthetic
processes. The study was led by researchers from the Max-Planck Institute for Molecular Plant
Physiology in Germany, Participating in the study was Dr. Haim Treves, a member of the School of
Plant Sciences and Food Security at Tel Aviv University, together with colleagues at the Max Planck
Institute for Molecular Plant Physiology in Germany. The study was published in the prestigious
journal Nature Plants.

In the framework of the study, the researchers sought to examine whether it is possible to improve
the efficiency of photosynthesis in plants, an energetic process that has been occurring in nature
for about 3.5 billion years. To try to answer this question, the researchers decided to focus on
green algae, particularly the Chlorella ohadii variety. This alga is known for its ability to survive in
extreme conditions of heat and cold, which forces it to exhibit resilience and grow very quickly.

The researchers assessed that a better understanding of Chlorella ohadii (named after the late
botanist Prof. Itzhak Ohad) would make it possible to improve the efficiency of photosynthesis in
other plants as well, and in turn to develop new engineering tools that could provide a solution for
sustainable food.

In the process of photosynthesis, plants and algae convert water, light and carbon dioxide into the
sugar and oxygen essential for their functioning. The researchers used innovative microfluidic
methods based on complex physical, chemical and biotechnological principles in order to provide
the algae with carbon dioxide in a measured and controlled manner and monitor the
photosynthesis “online.”

By using a comparative analysis, the researchers identified that there was a fundamental difference
in the photosynthesic processes carried out in in green algae compared to the model plants. They
assess that the difference lies in variations in the metabolic networks, a deeper understanding of
which will help in developing innovative engineering solutions in the field of plant metabolism, as
well as the optimal engineering of future agricultural products.

“Past empirical studies have shown that photosynthetic efficiency is higher in microalgae than in C3
or C4 crops, both types of plants that have transport systems but which are completely different in
terms of their anatomy and the way they carry out photosynthesis,” Dr. Treves explains. “The
problem is that the scientific community does not yet know how to explain these differences
accurately enough.”

Dr. Treves adds, “In our current study we mapped the patterns of energy production and
photosynthetic metabolism in green algae and compared them to existing and new data collected
from model plants. We were able to clearly identify the factors that influence the difference in
these patterns. Our research reinforces previous assessments that the metabolic pathway
responsible for recycling is one of the major bottlenecks in photosynthesis in plants. The next step
is to export the genes involved in this pathway and in other pathways in which we have detected differences from algae, and to test whether their insertion into other plants via metabolic engineering will increase their rate of growth or photosynthetic efficiency.

“The toolbox we have assembled will enable us to harness the conclusions from the study to
accelerate future developments in engineering in the field of algae-based sustainable food as a
genetic reservoir for plant improvement; monitoring photosynthetis is a quantitative and high-
resolution process, and algae offer an infinite source of possibilities for improving photosynthetic
efficiency.”

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