**AWARDS ISSUED PRIOR TO JANUARY 20, 2025, WERE FUNDED UNDER PREVIOUS ADMINISTRATIONS AND MAY NOT REFLECT THE PRIORITIES AND POLICIES OF THE CURRENT ADMINISTRATION.** PLANT PRODUCTIVITY IS GOVERNED BY THE PHOTOCHEMICAL-BIOCHEMICAL EVENTS LEADING TO CO2FIXATION AND ATP FORMATION AS WELL AS THE EFFICIENCY OF CONVERSION OF PHOTOSYNTHATE TO SUPPORT VEGETATIVE GROWTH AND ACCUMULATION OF STORAGE RESERVES IN DEVELOPING SINK ORGANS. RECENTDEVELOPMENTS HAVE INDICATED THAT IN ADDITION TO ITS ROLE IN STARCH INITIATION AND STARCH GRAINMATURATION, THE PLASTIDIAL PHOSPHORYLASE, PHO1, HAS A SECOND DISTINCTIVE ROLE IN PHOTOSYNTHESIS.THIS LATTER HYPOTHESIS IS SUPPORTED BY THE DEMONSTRATION BY FOUR INDEPENDENT METHODS (CO-IP, PULLDOWNS, YEAST 2-HYBRID AND BIFC), AND BY THE PRESENCE OF PHO1 WITH ISOLATED THYLAKOID CONTAINING PS1COMPLEXES THAT PHO1 INTERACTS WITH PSAC AND POSSIBLY OTHER TERMINAL COMPONENTS OF PHOTOSYSTEM I (PS I), A SYSTEM THAT TRANSFERS ELECTRONS FOR THE FORMATION OF NADPH OR REDUCED THIOREDOXIN. THE MECHANISM BY WHICH PHO1 IMPACTS PSI ACTIVITY AND WHY IT DOES SO REMAINS UNCLEAR, ALTHOUGH AN IMPORTANT ELEMENT IS THE PHO1'S L80, A PEPTIDE DOMAIN UNIQUE TO PLANTS AND NOT FOUND IN ANIMAL AND YEAST PHOSPHORYLASES. THE PRESENCE OF L80 IN PHO1 APPARENTLY NEGATIVELY MODULATES PSI ACTIVITY AS TRANSGENIC PHO1-MINUS MUTANT RICE PLANTS COMPLEMENTED WITH APHO1 GENE LACKING THE L80 PEPTIDE (PHO1ΔL80) DISPLAY INCREASED PLANT GROWTH RATES, BIOMASS,AND GRAIN WEIGHTS, ELEVATED PSI ACTIVITY, AND ENHANCED CO2 ASSIMILATION RATES COMPARED TO WILDTYPE PLANTS. IN THIS PROJECT, WE PROPOSE TO CONTINUE OUR COMPREHENSIVE ANDINTEGRATED RESEARCH PROGRAM TO STUDY HOW PHO1 AND ITS L80 DOMAIN CONTROLS THE SYNTHESISOF REDUCTANT VIA PSI AND, IN TURN, PLANT GROWTH AND DEVELOPMENT.

Washington State University, Pullman WA

Investigators