Light-induced formation of 13-cis violaxanthin in leaves of Hordeum vulgare

✍ Scribed by Denise Phillip; Peter Molnar; Gyula Toth; Andrew J. Young

• Book ID: 104373453
• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 648 KB
• Volume: 49
• Category: Article
• ISSN: 1011-1344
• DOI: 10.1016/s1011-1344(99)00019-6

✦ Synopsis

The ~ anthophyll cycle is recognized as one of several mechanisms involved in the protection of plant membranes against damage resulting from excess excitation in high light. However, in most plants, only a proportion ( typically ~ 60%) of violaxanthin undergoes de-epoxidation into zeaxanthin. When leaves of H. vulgare are illuminated at 650 p, mol m -2 s-~ of photosynthetically active radiation for 120 min, deepoxidation of violaxanthin is accompanied by trans ~ cis isomerization of this xanthophyll. The most significant change upon illumination is the formation of the 13-cis isomer from the all-trans form of this carotenoid. The level of the 13-cis isomer increases from ~ 1% of total violaxanthin in dark-adapted leaves to ~ 9% in leaves that have been illuminated. An identical pattern of isomerization for violaxanthin is also observed in leaves which are illuminated following pre-treatment with dithiothreitol (D'l"r). Following illumination, plants are returned to darkmess and recovery of the original isomeric content and composition is observed. The role of such light-mediated isomerization of violaxal~thin in terms of limiting de-epoxidation and its potential role in photoprotection of the light-harvesting complex is discussed.