Group leader: Szilvia Z. Tóth

Email: toth.szilviazita[at]brc.hu

Group website: https://www.szilviaztoth-brcszeged.com/

 

Group members


Name

Title

 

 

Szilvia Z. TÓTH

Senior research associate

publications

CV

László KOVÁCS

Senior research associate

publications

CV

Valéria NAGY

Research associate

publications

CV

Soujanya KUNTAM

Research associate

publications

CV

Tünde TÓTH

Research associate

publications

CV

Nia PETROVA

Research associate

publications

CV

Dávid TÓTH

Junior research associate

publications

CV

Eszter SZÉLES

Junior research associate

publications

CV

Tímea KÖRMÖCZI Scientific administrator publications CV

Éva HERMAN

Laboratory assistant

publications

CV

Research


Ascorbate (vitamin C) is a metabolite produced in plant cells that is essential for humans and has many functions in both plant and animal cells. Szilvia Z. Tóth and her research group invesitigate the intracellular transport, biosynthesis and physiological effects of ascorbate. Their other main area of research is the production of hydrogen gas (H2) by green algae, which could become a truly CO2-neutral energy source in the future, as only water is formed during the combustion of H2.

 

Physiological roles, biosynthesis and intracellular transport of ascorbate

 

Using different biochemical, molecular biological and biophysical methods, the group investigates the following issues:

 

  • Regulation of ascorbate biosynthesis in higher plants and green algae
    The biosynthesis of ascorbate in both plants and green algae occurs via the so-called “Smirnoff-Wheeler” pathway; however, they discovered that the regulation of their biosynthesis shows very significant differences (Vidal-Meireles et al., 2017; Tóth et al., 2018).

  • Intracellular transport of ascorbate
    Biosynthesis of ascorbate takes place in the mitochondria of plants, from which ascorbate is likely transported by transporter proteins to various cellular organelles. Surprisingly, however, so far only one ascorbate transporter (AtPHT4; 4, Miyaji et al., 2015) has been identified in plants, although several are likely to exist (Fernie and Tóth 2015). The research team is currently investigating homologues of the AtPHT4;4 transporter in the green alga Chlamydomonas reinhardtii.

 

Ascorbate biosynthesis in plants and green algae. In seed plants, ascorbate biosynthesis is dependent on light, photosynthesis and the circadian clock. In green algae, reactive oxygen species induce ascorbate biosynthesis, which is very rapid and intensive compared to plants. Modified from Tóth et al. (2018).

 

Development of microfluidic chambers for monitoring green algae

In order to understand the life processes of green algae as accurately as possible, we aimed to establish single cell analysis. Our approach is based on microfluidics, which allows the trapping of small numbers or individual algal cells for several days, during which we can perform morphological examinations under a microscope, and in combination with chlorophyll-a fluorescence, we can also obtain valuable information about photosynthetic activity.

 

Establishment of an entirely green renewable energy production system

H2 is a highly efficient and clean energy source. Photobiological H2 production by green algae could become a truly CO2-neutral energy source in the future, as only water is formed during the combustion of H2. [Fe-Fe] -type hydrogenases of green algae are the most efficient H2-producing catalysts known, but they are very sensitive to O2 formed during photosynthesis. This problem has been a major obstacle to achieving sustainable biohydrogen production over the past 40 years or so.

Significant H2 production can be achieved by sulfur deprivation, which leads to inactivation of photosystem II, the establishment of anaerobic conditions, and then the onset of H2 production. However, this process is unsustainable in the long run, very costly and cannot be applied on an industrial scale.

In contrast, we recently showed that after induction of hydrogenase enzymes by anaerobic treatment, their activity can be maintained if the activation of the Calvin-Benson cycle is prevented. This type of H2 production is highly efficient, completely photoautotrophic, and cultures remain photosynthetically active. By using O2 absorbent, we were able to significantly increase the efficiency of H2 production, and the current yields already significantly exceed the yields achieved by the commonly used sulfur removal method, thus getting closer to the realization of industrial H2 production (Nagy et al. 2018, Tóth and Yacoby 2019).

 

Photosynthetic electron transport and H2 production in green algae. Solar energy is captured by the light-harvesting complexes (LHC) of photosystems II and I (PSII and PSI). Electrons extracted from water by the oxygen evolving complex (OEC) of PSII are transferred to the photosynthetic electron transport chain to the Calvin-Benson cycle, which produces sugars and ultimately starch. Upon the induction of photosynthesis under hypoxic conditions, electrons are transferred to the hydrogenase (Hyd) and H2 is released. Modified from Tóth and Yacoby (2019).