Electron transport pathways in isolated chromoplasts from Narcissus pseudonarcissus L.

Abstract

During daffodil flower development, chloroplasts differentiate into photosynthetically inactive chromoplasts having lost functional photosynthetic reaction centers. Chromoplasts exhibit a respiratory activity reducing oxygen to water and generating ATP. Immunoblots revealed the presence of the plastid terminal oxidase (PTOX), the NAD(P)H dehydrogenase (NDH) complex, the cytochrome b 6 f complex, ATP synthase and several isoforms of ferredoxin-NADP + oxidoreductase (FNR), and ferredoxin (Fd). Fluorescence spectroscopy allowed the detection of chlorophyll a in the cytochrome b 6 f complex. Here we characterize the electron transport pathway of chromorespiration by using specific inhibitors for the NDH complex, the cytochrome b 6 f complex, FNR and redox-inactive Fd in which the iron was replaced by gallium. Our data suggest an electron flow via two separate pathways, both reducing plastoquinone (PQ) and using PTOX as oxidase. The first oxidizes NADPH via FNR, Fd and cytochrome b h of the cytochrome b 6 f complex, and does not result in the pumping of protons across the membrane. In the second, electron transport takes place via the NDH complex using both NADH and NADPH as electron donor. FNR and Fd are not involved in this pathway. The NDH complex is responsible for the generation of the proton gradient. We propose a model for chromorespiration that may also be relevant for the understanding of chlororespiration and for the characterization of the electron input from Fd to the cytochrome b 6 f complex during cyclic electron transport in chloroplasts.

Singlet fission in naturally-organized carotenoid molecules

“…al. 25 using a step gradient in which chromoplasts accumulate at the 15 % / 30 % sucrose interphase 27 . The isolated chromoplasts were suspended in 100 mM Tris/HCl pH 7.4, 10 mM MgCl2, 1 mM 1,4-dithioerythritol.…”

Physiological and Transcriptome Analyses Revealed the Mechanism by Which Deferoxamine Promotes Iron Absorption in Cinnamomum camphora

“…When plants are deficient in iron, the photosynthetic rate decreases, which leads to the disintegration of thylakoids, which inhibits photosynthesis. At the same time, the carotenoid and ferredoxin contents in the chloroplast pigment protein complex also decrease, which inhibits the synthesis of chloroplast precursors and reduces the chlorophyll content [ 44 ]. In this study, the active Fe and chlorophyll contents of camphor trees supplemented with deferoxamine increased significantly.…”

The impact of chromium ion stress on plant growth, developmental physiology, and molecular regulation

“…In duckweed ( Lemna minor ), with increasing treatment concentrations, the color of duckweed leaves gradually turned yellow, and the content of chlorophyll and carotenoids decreased significantly (Sallah-Ud-Din et al, 2017 ). Studies on Arabidopsis thaliana showed that chloroplast ribosomal recycling factors played an important role in chloroplast biosynthesis, and changes in maize protein under chromium stress suggested that chloroplast ribosomal recycling factors may be involved in the structure of chloroplast under chromium stress through post-translational modifications (Wang et al, 2013 ; Grabsztunowicz et al, 2019 ). Most of the identified chromium stress proteins (72%, 42/58) were predicted to be localized in the chloroplast, and these chloroplast-localized chromium stress proteins were associated with chloroplast structure and function, including the participation in photosynthesis electron transport, chloroplast organization, chlorophyll biosynthesis, and chloroplast redox balance.…”