Plant Researchers Henrik Aronsson and Emelie Lindquist are trying to identify the proteins at work in the chloroplasts. ‘We may find things in our chloroplasts that may help research on human cells,’ says Aronsson.

Plant Research with Links to the Nobel Prize

When this year’s winners of the Nobel Prize in Medicine were announced, Henrik Aronsson and his team of plant researchers at the University of Gothenburg jumped for joy. Like the Nobel laureates, the team studies vesicular transport, but not in the cell cytosol in yeast and mammals but in the chloroplasts of plant cells.
‘A Nobel Prize in this area brings attention to our research and helps people understand it better,’ says Aronsson.

The three Nobel laureates Rothman, Schekman and Südhof were awarded this year’s prize for their important discoveries concerning the transport system in cells. Each cell is like a factory that produces molecules and sends them to different places in the body. The molecules are transported in small packages called vesicles, and the trio has discovered how the molecules are transported to the right place in the cell at the right time.

Vesicular transport from the chloroplast membrane to the thylakoid membrane inside the chloroplasts where the photosynthesis occurs. Some proteins proposed to be involved in the transport are shown. VIPP1 (pink) and FZL (green) are found both at the sending and receiving membrane. SAR (purple) supports at the sending membrane – in an active form when forming vesicles and in an inactive form when returning to repeat the work. Rab (blue) supports at the receiving membrane. According to the working hypothesis, protein (red) can be transported as cargo inside the vesicles.

Vesicular transport from the chloroplast membrane to the thylakoid membrane inside the chloroplasts where the photosynthesis occurs. Some proteins proposed to be involved in the transport are shown. VIPP1 (pink) and FZL (green) are found both at the sending and receiving membrane. SAR (purple) supports at the sending membrane – in an active form when forming vesicles and in an inactive form when returning to repeat the work. Rab (blue) supports at the receiving membrane. According to the working hypothesis, protein (red) can be transported as cargo inside the vesicles. Figure made by Christel Garcia & Henrik Aronsson

The system inside plants works similarly, but the cells in plants also have chloroplasts. The chloroplasts contain thylakoids, which is where the critically important photosynthesis occurs. It is hypothesised that some of the building blocks in the form of proteins can be transported there, in small vesicular packages. Yet the details of this transport system remain largely unknown.
‘We do know how photosynthesis works, but don’t understand the design of the structure where it occurs, or how the system is formed,’ says Emelie Lindquist, doctoral student.

She is one of the researchers at the University of Gothenburg who, together with Aronsson, is trying to identify the proteins at work in the chloroplasts. Their working hypothesis is that there are proteins inside the vesicles that are delivered to the thylakoids.

The proteins in plant cells resemble those found in humans. Disruption of the vesicular transport in the human body can lead to a number of different diseases, including ADHD, cancer, epilepsy and schizophrenia. But we still don’t know how similar cells from plants and humans are. Perhaps chloroplasts have a unique system, or maybe the systems are very similar.
‘We may find things in our chloroplasts that may help research on human cells,’ says Aronsson.

It is not easy to identify the proteins inside chloroplasts. The plan is to eventually be able to isolate the vesicles in order to see what’s inside, but so far this has not been possible.

This type of research requires both advanced microscopes and a lot of time, and the researchers depend on cooperation with other research teams in Sweden and internationally. The next goal is to prove their hypothesis.
‘It’s not a simple process. There’s always something that gets in the way, but then suddenly it just clicks,’ says Aronsson, and Lindquist adds:

‘It would be great to prove our hypotheses in the near future.’

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