PRINCIPAL 



INVESTIGATOR(S) Geoffrey Hind 



Department of Biology 

 Brookhaven National Laboratory 

 Upton, NY 11973 



PROJECT TITLE THE XANTHOPHYLL CYCLE ENZYMES IN 



CHROMOPHYTE ALGAE AND PHYTOPLANKTON: 

 STRUCTURE AND SIGNIFICANCE 



AMOUNT OF FUNDING FY 1994: $0 K 



SUMMARY OF GOALS 



This project examines the detailed mechanisms that influence photosynthetic performance in 

 marine phytoplankton, specifically, nonphotochemical quenching of chlorophyll fluorescence. 

 This process is thought to dissipate excess excitation energy and limit the risk of photoinhibition 

 or photodestruction of pigment-protein complexes. One of the faster quenching components 

 correlates kinetically with establishment of a pH across the thylakoid membrane and the dark- 

 reversible de-epoxidation of a xanthophyll. The product (zeaxanthin or in chromophytes, 

 diatoxanthin) is the presumed quencher or quenching amplifier. Two enzymes function in this 

 cycle but information on their location, mode of action and structure is scant for higher plants, 

 and essentially lacking for phytoplankton. The goals of this project are: 1). to discover novel 

 inhibitors of the enzymes so that the status of the cycle can be "locked in" upon harvest, for later 

 shipboard analysis. These inhibitors will be used in collaborative work with Dr. Paul Falkowski 

 to evaluate photoprotection by the xanthophyll cycle in situ, 2). the isolation, cloning and 

 sequencing of the above enzymes as a basis for genetic manipulation e.g., selective gene transfer, 

 gene deletion or limitation of expression through synthesis of antisense message. 



SPATIAL AND TEMPORAL SAMPLING SCALES 



We propose a temporal sampling schedule that includes several 24-hr time series stations 

 occupied during different seasons. The effect of xanthophyll cycling and nonphotochemical 

 fluorescence quenching on phytoplankton photosynthesis is poorly understood. However, we 

 suggest these processes may be most important in surface waters during bright, sunny days when 

 zeaxanthin or diatoxanthin production is likely maximized. The spatial sampling scale will be 

 coordinated with other OMP investigators. 



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