ORT, Donald R.

Department of Plant Biology
Ph.D. (1974) Michigan State University

   Research Topics

• The Biochemical and Molecular Basis for Environmental Limitations on Photosynthesis

• Regulatory Control over Chloroplast ATP Synthase

• Low Temperature-Induced Limitations on Photosynthesis

• Chlorophyll Degradation in Canola Seeds

• Field Studies of Elevated Atmospheric CO2 and O3 on Soybean

   Research Interests  

   The long-range goal in this laboratory is to define how the component processes of photosynthesis integrate to determine performance under current and future agriculturally significant situations. Specific goals over the next 3 to 4 years follow.

   Investigate the underlying molecular basis of low temperature sensitivity of photosynthesis. In chilling-sensitive plants, low temperature interrupts the circadian control of the transcription of proteins required for the proper functioning of photosynthesis. Following a low temperature night, circadian control over sucrose phosphate synthase, nitrate reductase, and possibly the activity of other enzymes critical to leaf carbohydrate and nitrogen metabolism, is severely out of phase with the actual time of day. The current specific aims are to determine the molecular basis and the physiological consequences of the delay in timing of photosynthetic enzymes with particular focus on the chilling sensitivity of a protein phosphatase cascade that appears to function in transmitting circadian timing.

   Determine the hierarchy of regulatory control over the chloroplast ATP synthase. Three non-allelic nuclear mutants of Arabidopsis have been discovered in which regulation and activation of the ATP synthase has been altered. One mutation has been cloned in the g-subunit of the ATP synthase and shown to effect the redox regulation of the enzyme complex. The current specific aims are a) use complementation by transformation with site-directed ATP synthase g-subunit genes to investigate physiological role of redox regulation, and b) to complete map based cloning of a second of the ATP synthase mutants.

   Identify steps in chlorophyll degradation in canola seeds that are disrupted by freezing. Early frost causes millions of dollars in losses to canola farmers each year by disrupting chlorophyll degradation in seeds, which then contaminates and devalues the oil.  We are collaborating with Dr. John Whitmarsh in research to identify genes involved in the degradation of chlorophyll and chlorophyll binding proteins.  The specific aims are a) to identify reactions that are sensitive to freezing temperatures and b) identify the responsible enzymes and genes.  The longer-term goal is to design canola plants with improved seed chlorophyll degradation capabilities following freezing. 

   Develop, in cooperation with Drs. S. Long and E. DeLucia , a field-scale facility for investigating the impacts of elevated atmospheric CO2 and surface O3 on soybean using FACE (free-air- CO2-enrichment) technology. Current specific objectives are to: a) Identify whether soybean in the field is more or less vulnerable to low temperature/high light photoinhibition in elevated CO2. b) Determine if growth in elevated CO2 enhances or diminishes high temperature inhibition of photosynthesis in soybean.

   Key Words   Bioenergetics and Photosynthesis, Environmental Stress and Adaptations to Stress, Circadian Regulation

   Current Research Funding  BARD, USDA  

BTC Members