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Published on December 5, 2008; 10.1104/pp.108.131417

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Received October 16, 2008
Accepted December 1, 2008

De-novo Synthesis and Degradation of Lx- and V-cycle Pigments during Shade and Sun Acclimation in Avocado Leaves (P. americana)

Britta Forster *, C. Barry Osmond , and Barry J. Pogson

School of Biochemistry and Molecular Biology, Linnaeus Way, Building 41, The Australian National University, Canberra ACT 0200, Australia

* Corresponding author; email: britta.forster{at}anu.edu.au.

The photoprotective role of the universal violaxanthin cycle that interconverts viola (V)-, anthera (A)- and zea (Z)-xanthin is well established but functions of the analogous conversions of lutein-5,6-epoxide (Lx) and lutein (L) in the selectively occurring Lx-cycle are still unclear. We investigated carotenoid pools in Lx-rich leaves of avocado (Persea americana Mill.) during sun or shade acclimation at different developmental stages. During sun-exposure of mature shade leaves, an unusual decrease in L preceded the de-epoxidation of Lx to L and V to A+Z. In addition to de-epoxidation, de-novo synthesis increased the L and A+Z pools. Epoxidation of L was exceptionally slow, requiring about 40 days in the shade to restore the Lx pool, and residual A+Z usually persisted overnight. In young shade leaves, the Lx-cycle was reversed initially, with Lx accumulating in the sun and declining in the shade. De-novo synthesis of xanthophylls did not affect {alpha}- and {beta}-carotene pools on the first day, but during long-term acclimation {alpha}-carotene pools changed noticeably. Nonetheless, the total change in {alpha}- and {beta}-branch carotenoid pools was equal. We discuss the implications for regulation of metabolic flux through the {alpha}- and {beta}-branches of carotenoid biosynthesis, potential roles for L in photoprotection and Lx in energy transfer to photosystem II, and explore physiological roles of both xanthophyll cycles as determinants of photosystem II efficiency.




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C. Six, R. Sherrard, M. Lionard, S. Roy, and D. A. Campbell
Photosystem II and Pigment Dynamics among Ecotypes of the Green Alga Ostreococcus
Plant Physiology, September 1, 2009; 151(1): 379 - 390.
[Abstract] [Full Text] [PDF]


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