Formation of Starch New Gene Found Active in Starch Formation

Editor: M.A. Manja Wühr

Researchers at ETH Zurich have found a specific protein that significantly influences the formation of starch in plant cells. The findings may be useful in the food and packaging industries.

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Plant scientists of ETH found a new molecular factor in Arabidopsis which plays an important role in starch formation.
Plant scientists of ETH found a new molecular factor in Arabidopsis which plays an important role in starch formation.
(Picture: ETH Zürich/Seung D et al. 2015)

Zurich/Switzerland – Samuel Zeeman, professor of plant biochemistry at ETH Zurich, and his colleagues used model plant thale cress (Arabidopsis thaliana) to find other gene active in starch formation. However, they succeed: Protein Targeting to Starch (PTST). This gene encodes a protein that can bind temporarily to GBSS and starch, leading the former to its destination.

The researchers conducted experiments with mutant plants in order to clarify the role of PTST. These mutations suppress the formation of PTST, leading to the complete absence of amylose in the mutant plants, although the total starch content is as high as that found in wild plants.

New Gene is Taxi Driver

As a result, the plant researchers concluded that Arabidopsis is necessarily dependent on PTST for the formation of amylose. To their surprise the researchers discovered that GBSS, the most common enzymes bound to plant starch granules, was hardly detectable in the mutant plants.

But how could they explain that? By marking the two proteins with fluorescent substances, the researchers finally solved this riddle. GBSS needs PTST because it is the taxi that transports GBSS to the starch granules. After collecting GBSS, PTST‘parks’ briefly on the surface of the emerging starch granules in order to unload its cargo. Afterwards, PTST detaches itself again from the starch granule, while GBSS gets on with the synthesis of amylose. In addition, the transport protein appears to be necessary for the stability of GBSS – without PTST and the binding to the starch granule, it is unstable.

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