Recipient Organization
ARIZONA STATE UNIVERSITY
660 S MILL AVE STE 312
TEMPE,AZ 85281-3670
Performing Department
PLANT BIOLOGY
Non Technical Summary
Crop plants obtain their energy for growth and productivity by converting the energy from sunlight into chemically useful forms in a process termed photosynthesis. Light energy is initially captured and converted into chemical energy in specialized protein complexes termed reaction centers. In plants, two reaction centers, photosystem II and photosystem I, act in series to mediate the oxidation of water and the reduction of compounds subsequently used in later photosynthetic reactions. The objective of this project is to use genetic engineering to alter the photosystem I reaction center complex in a model plant cell system to gain a better understanding of its function, and develop procedures for improving the initial steps of photosynthesis. In photosystem I there exists two potential pathways for electron transfer, one or both of which may be active. We will address how individual amino acids modify the electronic properties of chlorophylls that function as the
primary electron donor and acceptor such that efficient photochemical electron transfer occurs. Genes encoding the PsaA and PsaB reaction center protein of photosystem I will be genetically altered to produce proteins with specific amino acid changes. The modified genes will be deposited onto very small gold particles and propelled into the cell by a gas discharge. Inside the cell, the altered genes integrate into the cellular genetic makeup and produce altered reaction center components. Using this approach we will produce a range of different mutant forms of the photosystem I reaction center and investigate how
Animal Health Component
(N/A)
Research Effort Categories
Basic
100%
Applied
(N/A)
Developmental
(N/A)
Goals / Objectives
The aim of this work is to understand the structure and function of the photosystem I reaction center complex. The PsA and PsaB subunits of the photosystem I complex bind the cofactors involved in charge separation and energy storage. The electron transfer cofactors form two potential electron transfer pathways. Our aim is to understand whether one or both branches are active in electron transfer by making mutants that perturb cofactors associated with one or the other branch. Analysis of the mutants will help us understand the mechanism of electron transfer events in photosystem I.
Project Methods
Site-directed mutagenesis will be used to introduce changes into the psaA or psaB gene in vitro. The modified genes will then be introduced in the chloroplasts of Chlamydomonas reinhardtii using the biolistics technique. Transformants will be selected by either complementation of a photosystem I minus mutant to restore photosynthetic growth capability transformation with chimeric gene constructs that bestow spectinomycin resistance to chloroplast transformants. Mutant cells and isolated photosystem I complexes will be studied using optical and electron paramagnetic resonance techniques.