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Understanding the Cell Biology of Starch Metabolism in Plants

English title Understanding the Cell Biology of Starch Metabolism in Plants
Applicant Zeeman Samuel C.
Number 182570
Funding scheme Project funding (Div. I-III)
Research institution Departement Umweltsystemwissenschaften ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Cellular Biology, Cytology
Start/End 01.02.2019 - 31.01.2023
Approved amount 997'822.00
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All Disciplines (2)

Discipline
Cellular Biology, Cytology
Botany

Keywords (5)

Arabidopsis thaliana; protein-protein interacions; starch granule initiation; protein-glucan interactions; starch biosynthesis

Lay Summary (German)

Lead
Stärke ist für uns von immenser Bedeutung, da sie der wichtigste Nährstoffbestandteil unserer Grundnahrungsmittel (wie z.B. Weizen oder Reis) darstellt. Darüber hinaus dient Stärke als Rohstoff für die Industrie. Stärke liegt als unlösliche Körner in Pflanzenzellen vor. Obwohl wir verstehen, welche Enzyme diese Stärkekörner bilden, verstehen wir nicht alle zellbiologischen Aspekte ihrer Herstellung - wo sie sich bilden, wie viele sich bilden und wie sie wachsen. Dieses Projekt befasst sich mit diesen Aspekten der Stärkebiosynthese in der Modellpflanze Arabidopsis thaliana.
Lay summary

Stärke ist das wichtigste Speicherkohlenhydrat von Pflanzen. Auch für uns ist Stärke von grosser Bedeutung, liefert sie doch etwa 50% unserer täglichen Kalorien. Stärke besteht aus Glukose, die zu massiven unlöslichen Körnern zusammengefügt wird. Unsere bisherige Forschung hat dazu beigetragen, die Bestandteile der pflanzlichen Maschinerie zu bestimmen, die die Stärkerkörner herstellt. In diesem Forschungsprojekt soll nun untersucht werden, wie Pflanzen diese Komponenten koordinieren und an bestimmte Stellen in der Zelle heften, um die gewünschte Anzahl von Stärkekörnern mit definierten Größen und Formen herzustellen. Um diese zellbiologischen Aspekte in der Modellpflanze Arabidopsis thaliana zu untersuchen, haben wir neuartige mikroskopische Techniken entwickelt. Zusammen mit genetischen Ansätzen sollen diese uns nun zeigen, wo innerhalb der Zelle sich die benötigten Enzyme befinden, wann und wo sich Stärkekörner bilden und welche Proteine den gesamten Prozess koordinieren. Diese Kenntnisse könnten dann dazu genutzt werden, die Qualität unserer Nutzpflanzen (z.B. Kartoffeln oder Getreide) zu verbessern, sei es durch Züchtung oder durch biotechnologische Methoden.

Direct link to Lay Summary Last update: 11.02.2019

Responsible applicant and co-applicants

Employees

Associated projects

Number Title Start Funding scheme
163503 Designing starch - harnessing carbohydrate polymer synthesis in plants 01.10.2015 ERA-CAPS
166487 Multi-dimensional imaging to visualize starch biosynthesis in plants. 01.07.2016 Interdisciplinary projects
153144 Understanding the Mechanism of Starch Biosynthesis in Plants 01.04.2014 Project funding (Div. I-III)

Abstract

Starch, the major storage carbohydrate in plants, is the single most important calorific component in our nutrition. Our societies depend on the cultivation of starch crops, including cereals and pulses, root and tuber crops. As well as food, starch is an important industrial feedstock, with diverse applications. It is critical we understand the biosynthesis of a substance on which we depend so heavily - the knowledge will serve society, supporting advances in agricultural production. Starch is chemically simple, being composed of polymers of glucose, but is unique as a biopolymer, forming insoluble, semi-crystalline granules with a complex internal architecture. Starch metabolism is highly conserved in plants and enormous insight and breakthrough discoveries have come from studies of the Arabidopsis model system, as well as from studies of starch crops themselves. We know which enzymes create and tailor the starch polymers and we recently recreated starch-like polymers the heterologous yeast system, Saccharomyces cerevisiae. Despite these advances in our biochemical understanding, many key cell-biological aspects of starch biosynthesis remain poorly understood. In particular, we know little about how starch granules are initiated in the plant. We have been assembling a unique combination of materials and cutting-edge cell-biological methods with which to open up this field.We previously identified two protein factors that contribute to starch granule biosynthesis in ways not previously observed. Designated PTST2 and PTST3 (for Protein Targeting to Starch), these non-enzymatic proteins influence starch granule initiation by delivering glucan substrates to the only other known granule initiation factor: Starch Synthase 4. We have now identified two additional, previously unstudied protein interactors and showed that they also affect granule initiation. Studying these proteins, and identifying others, forms the cornerstone of this proposal. We have also developed novel analytical techniques that provide detailed insight into the granule initiation process (including isotope labeling, electron tomography, Nano-SIMS), putting us in a strong position to poreform this work. We will determine the role of each of the currently known proteins implicated in granule initiation, establishing a functionally-validated protein-protein interaction network. Cutting-edge fluorescence microscopy will be used to define sub-domains within chloroplasts where starch granule initiation occurs. We will explore the co-localisation patterns of the proteins and the ways in which they are interdependent. We will use classical genetics and high-throughput screening to search for new factors influencing starch granule number and will study the glucan substrates used as initiation primers, focusing on mutants where both soluble glucan levels and granule initiation are affected.This work will reveal the cell biological mechanisms by which the plant’s biosynthetic apparatus is localized to control starch production elevating our understanding of this process in plants to a new level. We expect that the mechanisms we uncover will have broad relevance in plant cell biology and that we will also increase the toolkit for enhancing yield, nutritional and functional quality, and economic value of starch crops.
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