A Nitrate-Inducible Ferredoxin in Maize Roots (Genomic Organization and Differential Expression of Two Nonphotosynthetic Ferredoxin Isoproteins)

Abstract

We have identified and characterized a nitrate-inducible ferredoxin (Fd) i n maize (Zea mays L.) roots by structural analysis of the purified protein and by cloning of i t s cDNA and gene. In maize Fd isoproteins are encoded by a small multigene family, and the nitrate-inducible Fd was identified as a novel isoprotein, designated Fd VI, which differed from any Fd I to Fd V identified to date. In the roots of seedlings cultured without nitrate, Fd VI was undetectable.However, during the induction of the capacity for nitrate assimilation, the amount of Fd VI increased markedly within 24 h. Concurrentiy, the levei of transcript for Fd VI increased, but more quickly, reaching a maximal leve1 within 2 h with kinetics similar to those of nitrite reductase and Fd-NADP+ reductase. Fd 111 was constitutively expressed in roots, and no such changes at the protein and mRNA levels were observed during the nitrate induction. I n the 5' flanking region of the gene for Fd VI only, we identified NIT-2 motifs, which are widely found in genes for enzymes related to nitrogen metabolism. These data indicate that Fd V I i s co-induced with the previously characterized enzymes involved i n nitrate assimilation, and they suggest that the novel Fd isoprotein, distinct from the constitutively expressed Fd, might play an important role as an electron carrier from NADPH to nitrite reductase and other Fd-dependent enzymes in root plastids.

A Post Genomic Characterization of Arabidopsis Ferredoxins

“…This is in contrast to maize, where two separate isoforms have been described (Matsumura et al, 1997): one constitutively expressed and one nitrate induced. In agreement with measurements taken for maize root type Fd, AtFd3 has a more positive redox potential than leaf type Fds, favoring its reduction under non-photosynthetic conditions.…”

“…1A), AtFd1 and AtFd2 share many residues specific to leaf type Fds, and in support of this, light regulation of the AtFd2 gene has been reported (Vorst et al, 1993). On the basis of amino acid sequence comparison, AtFd3 encodes a typical root type Fd, and Wang et al (2000) found expression of this gene was nitrate inducible, reminiscent of a root type Fd from maize (Matsumura et al, 1997). The AtFd4 protein differs from all well-studied wild-type Fds at several residues.…”

Photosynthetic fuel for heterologous enzymes: the role of electron carrier proteins

“…These include a root isoform, which supports NADP + reduction less efficiently partly because it possesses a redox potential close to the NADP + /NADPH couple (Matsumura et al 1997;Hanke et al 2004;Terauchi et al 2009). Because ferredoxins involved in photosynthesis support the reduction of NADP + to NADPH, they have redox potentials much more negative than those required for the reduction of, e.g., cytochrome P450s, whose reductases possess redox potentials of −200 to −270 mV (Das and Sligar 2009;Simtchouk et al 2013).…”

Cloning and Inactivation of Genes Encoding Ferredoxin- and NADH-Dependent Glutamate Synthases in the CyanobacteriumPlectonema boryanum. Imbalances in Nitrogen and Carbon Assimilations Caused by Deficiency of the Ferredoxin-Dependent Enzyme1

“…The mutant grows normally in darkness and under conditions of anaerobic nitrogen fixation (data not shown). Therefore, nitrogen assimilation can be supported solely by Fd-GOGAT under conditions in which photoreducing power is not available, suggesting that a system for the donation of electrons from NADPH to Fd is operative, as it is in the roots of higher plants (Matsumura et al, 1997). We have not succeeded in generating a double mutant with both genes inactivated.…”