Differential Interaction of Maize Root Ferredoxin:NADP+ Oxidoreductase with Photosynthetic and Non-Photosynthetic Ferredoxin Isoproteins

Abstract

In higher plants ferredoxin (Fd):NADP ϩ oxidoreductase (FNR) and Fd are each distributed in photosynthetic and nonphotosynthetic organs as distinct isoproteins. We have cloned cDNAs for leaf FNR (L-FNR I and L-FNR II) and root FNR (R-FNR) from maize (Zea mays L.), and produced recombinant L-FNR I and R-FNR to study their enzymatic functions through kinetic and Fd-binding analyses. The K m value obtained by assay for a diaphorase activity indicated that R-FNR had a 10-fold higher affinity for NADPH than L-FNR I. When we assayed for NADPH-cytochrome c reductase activity using maize photosynthetic Fd (Fd I) and non-photosynthetic Fd (Fd III), the R-FNR showed a marked difference in affinity between these two Fd isoproteins; the K m for Fd III was 3.0 m and that for Fd I was 29 m. Consistent with this, the dissociation constant for the R-FNR:Fd III complex was 10-fold smaller than that of the R-FNR:Fd I complex. This differential binding capacity was confirmed by an affinity chromatography of R-FNR on Fd-sepharose with stronger binding to Fd III. L-FNR I showed no such differential interaction with Fd I and Fd III. These data demonstrated that R-FNR has the ability to discriminate between these two types of Fds. We propose that the stronger interaction of R-FNR with Fd III is crucial for an efficient electron flux of NADPH-FNR-Fd cascade, thus supporting Fd-dependent metabolism in non-photosynthetic organs.

In-Depth Analysis of the Thylakoid Membrane Proteome ofArabidopsis thalianaChloroplasts: New Proteins, New Functions, and a Plastid Proteome Database[W]

“…In A. thaliana, contrasting reports concerning such functional substitution of both PC proteins by cytochrome c6 were reported (Gupta et al, 2002;Weigel et al, 2003). Two out of three FNR proteins were identified in the organic solvent fractions, in agreement with observations that chloroplasts expressed two FNR isoforms, whereas the third one is expressed in nonphotosynthetic plastids (Onda et al, 2000). An FNR protein was identified as a component of the cytochrome b6f complex in Spinacia oleracea (spinach) (Zhang et al, 2001) and is possibly the ortholog of At1g20020 (FNR-2).…”

“…We identified 83 of those 99 proteins, as detailed below. Some of the undetected proteins are likely only expressed in nongreen plastids (FNR-3) (Onda et al, 2000) or possibly only under particular conditions (cytochrome c6), as in Chlamydomonas reinhardtii (Quinn and Merchant, 1998). As we discuss below, we were able to identify an additional 100 nonphotosynthetic proteins implicated in biogenesis and oxidative stress responses or without known function.…”

Bioenergetics of Monoterpenoid Essential Oil Biosynthesis in Nonphotosynthetic Glandular Trichomes

“…4). Thus far, nonphotosynthetic Fd and FNR isoforms have only been characterized from roots (Hanke et al, 2005;Aliverti et al, 2008;Onda et al, 2000); therefore, it was of interest to evaluate which isoforms are present in nonphotosynthetic GTs.…”

Decreased Content of Leaf Ferredoxin Changes Electron Distribution and Limits Photosynthesis in Transgenic Potato Plants

“…Fds from heterotrophic sources are different in both amino acid sequences and biochemical characteristics from the Fds in photosynthetic tissues (Onda et al, 2000). In non-photosynthetic plastids, e.g.…”