USDA ARS

Molecular biochemical basis for environmental effects on photosynthesis and photosynthetic energy transduction

The Ort Lab

Current Research:

Impacts of increasing atmospheric carbon dioxide and tropospheric ozone on photosynthesis and productivity of soybean and corn

AndySoy Don Ring

Corn-Soybean is the largest ecosystem in the US, dominating the Midwest. SoyFACE a unique open-air laboratory that uses fast-feedback control technology to treat large growing areas with future levels of carbon dioxide and ozone. We are investigating the effects of atmospheric change on photosynthesis and canopy energy balance, as well as the interaction of increased atmospheric carbon dioxide and drought. Currently, the Ort Lab is interested in determining the ensembles of genes underlying the genetic variability of water use efficiency in soybean and the response of this variability to the interacting effects of elevated carbon dioxide and ozone.

Green Seed Problem in Canola

CanolaSeeds

Developing canola seeds are green due to chloroplasts located primarily in the seed embryo. As the canola seed matures the photosynthetic components of the chloroplast are normally degraded in a coordinated process that includes the enzymatic breakdown of chlorophyll into colorless catabolites, yielding a mature seed that is essentially free of chlorophyll. Cold hardiness is a sought after trait in canola in part because exposure to freezing temperatures during early seed development can disrupt normal chlorophyll degradation, resulting in mature seeds that remain green, greatly devaluing the resulting oil. We have shown that freezing interferes with the later phases of canola seed development when chlorophyll is supposed to be cleared from the seed. Specifically affected is pheophorbide a oxygenase (PaO), the enzyme responsible for the opening of the porphyrin macrocycle, a critical decolorizing step in chlorophyll degradation. Moreover, we found that the regulation of PaO activity is largely post-translational and it is at this level where freezing interferes with PaO activation in canola seeds (Chung et al., 2006). We have generated PaO RNAi transformants in Arabidopsis and find an inverse dependence between the expression level of PaO transcript and chlorophyll retention in dark senescing leaves (Chung, D and Ort DR, unpublished). This and other pieces of evidence suggest that PaO, and thus probably chlorophyll degradation, may be regulated differently in senescing leaves than in maturing seed. We plan to explore this in more depth following a similar strategy to that we used for seeds.

Cool temperatures and warm climate crops

canolatomato

Many important agronomic species grown in temperate climates originated in warmer tropical and subtropical regions (e.g., corn, soybean, cotton, tomato). Unlike the native species of temperate climates, most of the plants from tropical/subtropical origins have little capacity to acclimate to cool, much less freezing, temperatures. The relevant physiological basis of chilling sensitivity depends not only on the seasonal climatic conditions of the target growing region, but also whether the low temperature episodes occur at night or in the light, as well as the species of warm climate plant. The cool-temperature sensitivity of these crops plays a central role in determining the growing range as well as annual variations in their economic success, thus there is an intense interest in discovering the mechanistic bases for low temperature sensitivity. It is hoped that by defining the primary chilling-induced lesions that cause the metabolic dysfunctions in warm climate plants it will be possible to devise strategies to minimize this sensitivity.

Genomic Ecology of Global Change

How ecosystems will respond to rapid changes in climate represents one of the great scientific challenges of this century. Human activities are altering the composition of our atmosphere (carbon dioxide and ozone), affecting the Earth's climate system (elevated temperature and water deficits) and introducing invasive species, thus altering the capacity of native and agro-ecosystems to provide critical goods and services including food, fiber, fuel, clean air and water. The University of Illinois has established the only facility worldwide for studying the simultaneous effects of rising carbon dioxide, ozone, and drought on plants under completely open-air conditions. The aim of the "Genomic Ecology of Global Change" theme within the Institute of Genomic Biology is to produce the scientific foundation to use information obtainable at the level of genomes and proteomes of species and communities to predict the effect of environmental changes on the structure and function of ecosystems. Mathematical modeling and bioinformatics provide the conceptual foundation and data analysis tools for making sound scientific inference. To achieve this aim, we have assembled an interdisciplinary team of eight faculty spanning molecular to ecological research, within an overarching link of mathematical modeling and informatics.

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last updated April 3, 2007
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