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United States Department of Agriculture

Agricultural Research Service

Research Project: Identifying and Manipulating Key Determinants of Photosynthetic Production and Partitioning

Location: Global Change and Photosynthesis Research Unit

Project Number: 5012-21000-027-00
Project Type: Appropriated

Start Date: May 31, 2013
End Date: May 30, 2018

Objective:
Objective 1: Engineer improved photosynthetic efficiency in food, feed, and biofuel crops for improved yields. 1.1 Determine the optimal chlorophyll (Chl) content to maximize the daily integral of canopy photosynthesis. 1.2 Decrease photorespiration by improving the effectiveness of engineered chloroplast photorespiratory bypass pathways by lowering the activity of the chloroplast glycolate exporter. Objective 2: Define the key posttranslational regulatory factors controlling assimilation/partitioning and growth in crop plants. 2.1 Investigate historical and diverse soybean germplasm to study fundamental interactions and constraints between carbon and nitrogen metabolism, and their influence on soybean yield and seed quality. 2.2 Characterize the brassinosteroid (BR) receptor kinase, BRI1, and identify phosphosites that can be manipulated by directed mutagenesis to alter kinase activity or specificity. 2.3 Identify protein interactors with key receptor kinases with specific attention to those where the interaction is phosphorylation dependent and/or plays a regulatory role. Objective 3: Determine the major features, physiological and genetic, and the mechanistic basis for the response of crops to elevated atmospheric CO2 and tropospheric ozone, and determine their interactions with temperature and drought. 3.1 Investigate the response of growth, photosynthesis and carbohydrate metabolism to elevated CO2 in species with different phloem loading strategies. 3.2 Use functional genomic and quantitative genetic approaches to dissect the genetic basis for ozone tolerance in crops. 3.3 Investigate and compare the physiological and agronomic responses of maize and soybean to heat waves. Objective 4: Determine the linkages between whole plant, physiological and genetic, and ecosystem processes to maximize key ecosystem services for current and alternative bioenergy production systems in the context of carbon, water, and nutrient cycling and energy partitioning. 4.1 Investigate the benefits associated with improving photosynthetic efficiency and/or light attenuation through crop canopies that extend beyond higher productivity. 4.2 Model the regional impacts of improved carbon uptake, carbon sequestration in soils, greenhouse gas emissions, and canopy water use on local- and regional-scale biogeochemical cycles using coupled biosphere-atmosphere-hydrology models. 4.3 Investigate through field measurements and mechanistic ecosystem models the impact of land-use change to accommodate bioenergy feedstock species on regional productivity and ecosystem services.

Approach:
The overall goal of this research is to identify molecular, biochemical, and genetic determinants of photosynthate production and distribution in crop plants and to utilize this new information to address specific agricultural problems of national importance including those associated with atmospheric change. The experimental approaches are diverse combining biophysics, biochemistry, physiology, molecular biology, and genomics with both laboratory and field components. The approaches used to meet the goals of Objective 1 for improving photosynthetic efficiency of crop plants will center on developing a canopy light energy distribution and two separate strategies to lower soybean leaf chlorophyll. Objective 2 that seeks to key regulatory steps controlling assimilation, partitioning and growth will be approached using a "common garden" experiment with historical soybean cultivars, site directed mutagensis of phytohormone receptors and yeast two-hybrid procedures to find interacting partners of the receptors. Objective 3 involves determining factors controlling the response of crops to global change factors will use Free Air Concentration Enrichment technology (FACE) to impose interacting treatments in a replicated factorial experimental design under field conditions. Objective 4 is intended to discover linkages that scale from leaves to ecosystem responses where the approach relies centrally on large scale flux measurements by eddy covariance technologies.

Last Modified: 11/22/2014
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