10.04.2014

Key finding in the process of photosynthesis

Argentine scientists discovered a new pathway in which the chloroplast, responsible for photosynthesis, affects gene expression on the variation in lighting conditions.

(from left to right) Micaela Godoy Herz, Lino Barañao and Alberto Kornblihtt during the presentation.

(from left to right) Micaela Godoy Herz, Lino Barañao and Alberto Kornblihtt during the presentation.

The Minister of Science, Technology and Productive Innovation, Lino Barañao, led the presentation of Alberto Kornblihtt, about the discovery of a new mechanism involved in regulating the response of plants to light variation. This research, conducted by the team at the Institute of Physiology, Molecular Biology and Neuroscience (IFIBYNE) of the National Council for Scientific and Technical Research (CONICET) and the Universidad de Buenos Aires (UBA), was published today in the journal Science. The paper, highlighted by the prestigious scientific journal, bears the signatures of its first authors, Ezequiel Petrillo, who is currently a post doctorate researcher at Max F. Perutz Laboratories of the University of Viena, Austria, and the postdoctoral fellow Micaela Godoy Herz of the IFIByNE.

Barañao: ""the number of publications of Argentine researchers in first level scientific journals has been multiplied by seven in a decade"

In this regard, the Ministry of Science said that "the number of publications of Argentine researchers in first level scientific journals has been multiplied by seven in a decade" and he added that "some time ago Argentine researchers had to work in another country or make cooperation with foreign research institutes to make get their papers published". Finally, Minister Barañao said that "fortunately, we can show that science activities entirely conducted in Argentina are highly competitive". 

Photosynthesis, the process by which plants and algae cells transform inorganic substances into organic substances through the use of light energy, is a mechanism described in depth from the nineteenth century. However, it was unknown up to now that photosynthesis also senses the light to control the plant cell nucleus and regulate the number of different proteins that each of its genes can generate, in response to different conditions of lighting/darkness.

The researchers showed that this sensor sending the signal to the nucleus is the chloroplast, the organelle responsible for photosynthesis. "When illuminated, plants change the alternative splicing of many genes compared to what happens in the darkness", said Alberto Kornblihtt, senior researcher at CONICET in the IFIBYNE, professor at the School of Exact and Natural Sciences (FCEyN -UBA) and director of the research.

Upon variations in the light intensity, the chloroplast sends signals to the cell nucleus modifying the alternative splicing of a gene and triggers a series of responses in the plant.

The alternative splicing is the mechanism by which different proteins may be obtained from a single gene through selective cutting and adhering of sections of messenger ribonucleic acid (RNA) that is the "mold" of the information contained within the gene.

The team discovered that the signal generated by the chloroplast affects the proportions of the three messengers RNA (mRNA1, mRNA2 and mRNA3) obtained from alternative splicing of a particular gene. While the 2 and 3 forms are retained in the nucleus, the mRNA1 passes to the cell cytoplasm where it is translated to the At- RS31 protein.

Precisely, the signal from the chloroplast to the core increases the proportion of the mRNA1 and therefore to the protein. This signal ceases over long periods of darkness or low light intensity, and as a result the plants undergo substantial changes: they are smaller, yellowish and chlorophyll degrades rapidly, "being less resistant to adverse conditions" said Ezequiel Petrillo, first author of the study.

While researchers continue to study about what cellular mechanisms acts At- RS31, it is known that this protein is a splicing factor, i.e. acting and modifying the alternative splicing of other genes. “This regulation is important for the plant, since if this process is interrupted has serious difficulties to grow and thrive; not in normal cycles, but in extreme situations either of prolonged lighting or darkness" Kornblihtt analyzes.

But also during the study the researchers showed that the signal given by the chloroplast can go from the leaves to the roots, whose cells do not have this organelle, and modify the alternative splicing occurring in their nuclei. "The signal generated by the chloroplast in response to the light in the leaves is able to communicate to non - photosynthetic tissues, such as the root, the same information, triggering similar changes in gene expression of these distant tissues", explains Petrillo.

Between 2003 and 2011, the research team received subsidies from the National Agency for Science and Technology Promotion under the Ministry of Science for a total of $ 3,462,548. They also received contributions from the CONICET, the University of Buenos Aires, the Howard Hughes Medical Institute and the Alternative Splicing Network of the European Union (EURASNET).

 

Evolutionary history

Kornblihtt explains that chloroplasts were originally photosynthetic bacteria and about 1,500 million years ago were incorporated into other existing cells, with which a symbiotic relationship was established.

Until now it was known that the chloroplast provides to the cell with the ability to do photosynthesis; however the description of its role as a sensor of light intensity and regulation of the alternative splicing of genes opens the door to future research.

"It's not enough to know what genes are turned on or off in animal and plant cells" emphasizes Kornblihtt , "in the case of those which are on, the variant of the protein produced and under what conditions are necessary to be known to determine their role".

 

Authors of the research

- Ezequiel Petrillo. Max F. Perutz Institute, Medical University of Vienna. Austria.

- Micaela A. Godoy Herz. Doctoral Fellow IFIBYNE.

- Armin Fuchs. Max F. Perutz Institute, Medical University of Vienna. Austria.

- Dominik Reifer. Max F. Perutz Institute, Medical University of Vienna. Austria.

- John Fuller. James Hutton Institute, Invergowrie. Dundee University. Scotland.

- Marcelo J. Yanovsky. Independent Researcher. Institute of Biochemical Research in Buenos Aires. Leloir Institute Foundation

- Craig Simpson. James Hutton Institute, Invergowrie. Dundee University. Scotland.

John W. S. Brown. James Hutton Institute, Invergowrie. Dundee University. Scotland.

- Andrea Barta. Max F. Perutz Institute, Medical University of Vienna. Austria.

- Maria Kalyna. Max F. Perutz Institute, Medical University of Vienna. Austria.

- Alberto R. Kornblihtt. Senior Research Fellow. IFIBYNE.

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  • (from left to right) Micaela Godoy Herz, Lino Barañao and Alberto Kornblihtt during the presentation.
  • Micaela and Alberto Godoy Herz Kornblihtt in the laboratory of Physiology and Molecular Biology IFIByN
  • Michelle Godoy Herz, PhD Fellow at CONICET IFIBYNE.
  • The intern Michelle Godoy Herz Minister Lino Barañao, the researcher Alberto Kornblihtt and manage IFIBYNE, Osvaldo Uchitel.
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(from left to right) Micaela Godoy Herz, Lino Barañao and Alberto Kornblihtt during the presentation.

(from left to right) Micaela Godoy Herz, Lino Barañao and Alberto Kornblihtt during the presentation.

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