Characterization of promoter elements required for expression and induction by sucrose of the Arabidopsis COX5b-1 nuclear gene, encoding the zinc-binding subunit of cytochrome c oxidase

Abstract

Arabidopsis COX5b-1 encodes an isoform of the zinc binding subunit 5b of mitochondrial cytochrome c oxidase. A promoter region required for expression and induction by sucrose of this gene was analyzed using plants stably transformed with mutagenized promoter fragments fused to the gus reporter gene. Promoter dependent expression is absolutely dependent on a G-box present at -228 from the translation start site. This element interacts in vitro and in vivo with transcription factors from the bZip family, preferentially with the abscisic acid-responsive element binding factor AREB2/ABF4. A region located upstream of the G-box (-333/-259) contains elements with the core sequence ATCATT and distalB-like sequences (CCACTTG) that are required for expression in vegetative tissues. These sequences bind different sets of proteins present in plant nuclear extracts and participate in induction by sucrose (ATCATT) and abscisic acid (distalB) of the COX5b-1 promoter. We propose that the COX5b-1 promoter has acquired novel regulatory mechanisms during evolution after gene duplication. These novel mechanisms have allowed the diversification of expression patterns, but also the conservation of some responses that, as induction by sucrose, are shared by COX5b-1 and other genes encoding components of the mitochondrial respiratory chain. Conservation of these responses may be a pre-requisite for the successful incorporation of new regulatory elements in this class of genes.

The Transcription Factor ABI4 Is a Regulator of Mitochondrial Retrograde Expression of ALTERNATIVE OXIDASE1a

“…These interactions are also likely to be integrated with other signals, as several other elements have previously been characterized in the AOX1a promoter (Dojcinovic et al, 2005;Ho et al, 2008). ABREs containing the core binding site of ACGT have been previously shown to be present and active in the promoter regions of genes encoding proteins of the mETC, specifically from COX5b-1 (for cytochrome oxidase subunit 5b; Comelli et al, 2009) and SDH2-3 (for succinate dehydrogenase subunit 2-3; Roschzttardtz et al, 2009), which bind AREB2/ABF4 and ABI3, respectively. In this study, the binding of ABI3 to the AOX1a B element region in the yeast one-hybrid assays may be explained by the fact that both the B element and the ABRE element (one of the ABI3 binding sites; Hattori et al, 1995) contain a CGT(G) core sequence.…”

Chlorophyll b Reductase Plays an Essential Role in Maturation and Storability of Arabidopsis Seeds

“…This protein is readily abundant in the early phase of seed maturation (Ruuska et al, 2002). We used a truncated form of the ABF4 protein that consists of the bZIP domain (amino acids 331-440) because previous reports indicated the difficulties in expressing full-length ABF4 (Comelli et al, 2009). Biotin-labeled DNA nucleotides, comprising 2294 to 2234 of the NYC1 promoter, were tested for interaction with the truncated form of the ABF4 protein.…”

Ectopic overexpression of AtmiR398b gene in tobacco influences seed germination and seedling growth

“…Of those three genes, CSD1 and CSD2 encode copper/zinc superoxide dismutases which scavenge ROS by converting O 2-to H 2 O 2 in higher plants (Fridovich 1995). Similarly, Arabidopsis COX5b-1 encodes the subunit 5b of mitochondrial cytochrome c oxidase (Comelli et al 2009). The mRNAs of three target genes are posttranscriptionally cleaved by miR398.…”