IMMUTANS Does Not Act as a Stress-Induced Safety Valve in the Protection of the Photosynthetic Apparatus of Arabidopsis during Steady-State Photosynthesis

作者：Dominic Rosso, Alexander G. Ivanov, Aigen Fu, Jane Geisler-Lee, Luke Hendrickson, Matt Geisler, Gregory Stewart, Marianna Król, Vaughan Hurry, Steven R. Rodermel, Denis P. Maxwell, Norman P. A. Huner · 发表于：PLANT PHYSIOLOGY · 年份：2006 · DOI：10.1104/pp.106.085886 · 被引用次数：118 · 研究领域：Photosynthetic Processes and Mechanisms、Plant Stress Responses and Tolerance、Mitochondrial Function and Pathology

IMMUTANS (IM) encodes a thylakoid membrane protein that has been hypothesized to act as a terminal oxidase that couples the reduction of O(2) to the oxidation of the plastoquinone (PQ) pool of the photosynthetic electron transport chain. Because IM shares sequence similarity to the stress-induced mitochondrial alternative oxidase (AOX), it has been suggested that the protein encoded by IM acts as a safety valve during the generation of excess photosynthetically generated electrons. We combined in vivo chlorophyll fluorescence quenching analyses with measurements of the redox state of P(700) to assess the capacity of IM to compete with photosystem I for intersystem electrons during steady-state photosynthesis in Arabidopsis (Arabidopsis thaliana). Comparisons were made between wild-type plants, im mutant plants, as well as transgenics in which IM protein levels had been overexpressed six (OE-6 x) and 16 (OE-16 x) times. Immunoblots indicated that IM abundance was the only major variant that we could detect between these genotypes. Overexpression of IM did not result in increased capacity to keep the PQ pool oxidized compared to either the wild type or im grown under control conditions (25 degrees C and photosynthetic photon flux density of 150 micromol photons m(-2) s(-1)). Similar results were observed either after 3-d cold stress at 5 degrees C or after full-leaf expansion at 5 degrees C and photosynthetic photon flux density of 150 micromol photons m(-2) s(-1). Furthermore,...