Martin, Mercedes , Sabater, Bartolome , Serrot, Patricia , Pradanos, Carlos .
Requirement of the plastid ndh genes for photosynthetic land adaptation.
The plastid ndh genes encode components of thylakoid Ndh complex which catalyses the transfer of electrons from NADH to plastoquinone. Through chlororespiration, the Ndh complex provides (while other activities drain) electrons to poise the redox level of the cyclic photosynthetic electron transporters under rapidly fluctuating temperatures, CO2 supply and light intensity. Otherwise, photoinhibition of photosystem II and, in general, damage by reactive oxygen species produced by excess light would fatally impair the functioning of the photosynthetic machinery. Consequently, the adaptation of the rate of photosynthesis to changing light intensities is slower in transgenic tobacco defective in the Ndh complex than in wild type. On the other hand, over-expression of the ndh genes triggers the production of reactive oxygen species inducing programmed cell death in leaves. We also found the ndh genes and the Ndh complex in Pinus thunbergii, whose plastid DNA was first reported to contain only ndh pseudogenes, indicating that the Ndh complex is present in all photosynthetic plants. Accordingly, the ndh genes have been found in the plastid DNAs of all members of the green line leading from Charophyta algae to higher plants, which suggests that the Ndh complex was essential for the adaptation of photosynthesis to land. Probably, deep water habitats and motility mitigate the effect of light intensity changes on the redox level of electron transporters in noncharophycean algae that lost the ndh genes, originally present in cyanobacteria, during the evolution of chloroplasts.
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WEB site Dr. B. Sabater
WEB site Dr. M. Martín
1 - Alcalá University, Plant Biology, -University campus-, Alcalá de Henares-Madrid, 28871, Spain
2 - Alcalá University, Plant Biology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM