Occurrence and operation of the lutein epoxide cycle in Quercus species.

A new xanthophyll cycle involving de-epoxidation of lutein epoxide into lutein in the light and epoxidation back in the dark has been recently described in parasitic plants. In the present work, the presence of the non-ubiquitous lutein epoxide was detected in many different non-parasitic woody plant species. Phylogenetic constraints are critical for the presence of this xanthophyll, since the largest amounts are found within the Fagaceae family and mainly in the genus Quercus. Irrespective of their ecological characteristics, this xanthophyll was found in eight Quercus species. Under photoinhibitory conditions lutein epoxide decreased in parallel with violaxanthin, and a concomitant increase in lutein was observed, indicating operation of this cycle in the genus Quercus. However, recovery in darkness differed from that of the xanthophyll cycle. It is also shown that lutein epoxide content is higher in shade leaves, especially during summer. The operation of this cycle could also contribute to photoprotection mechanisms of evergreen Quercus species during winter.