A segment containing a G-box and an ACGT motif confers differential expression characteristics and responses to the Arabidopsis Cytc-2 gene, encoding an isoform of cytochrome c

Abstract

Sequences required for the expression of Cytc-2 (At4g10040), one of two cytochrome c genes from Arabidopsis thaliana, were characterized using plants transformed with deleted and mutagenized promoter fragments fused to gus. These studies indicated that a region containing a G-box and an ACGT motif is essential for expression. Mutation of the ACGT motif causes a complete loss of expression, while mutation of the G-box causes decreased expression in aerial parts and abolishes expression in roots and induction by environmental factors. Upstream located site II elements are required for maximal expression, mainly in reproductive tissues, and maximal induction by different factors. One-hybrid screenings allowed the identification of transcription factors from the bZIP and bHLH families that interact mainly with the G-box. Four of these factors were able to bind to the Cytc-2 promoter in vitro and in transactivation assays in Arabidopsis. Analysis of available microarray data indicated that the bZIP transcription factors share expression characteristics with the Cytc-2 gene, suggesting that they act as mediators of its response to tissue-specific, environmental, and metabolic conditions. Site II elements interact with a TCP family protein and may co-ordinate the expression of the Cytc-2 gene with that of other respiratory chain components. A model is proposed for the evolution of the Cytc-2 gene through the incorporation of a segment containing a G-box and an ACGT motif into an ancestral gene that contained site II elements. This may have reduced the importance of site II elements for basal expression and conferred new responses to environmental factors.

A Functional Antagonistic Relationship between Auxin and Mitochondrial Retrograde Signaling Regulates Alternative Oxidase1a Expression in Arabidopsis

“…Thus, although the altered auxin homeostasis described here results in the negative regulation of AOX1a, auxin response itself may also be positively regulated by mitochondrial function through TEOSINTE BRANCHED1 CYCLOIDEA (TCP) and proliferating cell nuclear antigen factor transcription factors (Koyama et al, 2010). TCPs are important redoxsensitive regulators of genes encoding mitochondrial proteins for components of the respiratory chain and are involved in mitochondrial biogenesis (Welchen and Gonzalez, 2005;Gonzalez et al, 2007;Welchen et al, 2009;Giraud et al, 2010). TCP transcription factors are master regulators of ribosomal proteins, and specifically, TCP21 interacts with TIMING OF CAB EXPRESSION1 to bind to the CIRCADIAN CLOCK ASSOCIATED1 promoter, establishing a link to the core clock components (Martín-Trillo and Cubas, 2010).…”

A PPR protein involved in regulating nuclear genes encoding mitochondrial proteins?

“…In contrast genes encoding components of alternative respiratory pathways do not show a particular prevalence for site II elements. 12,13 The hypothesis of the involvement of site II elements and TCP transcription factors in the expression of mitochondrial proteins has been confirmed recently, 14,15 in particular through the finding that TCP transcription factors mediate the coordinated expression of mitochondrial proteins during the circadian cycle. 16 In this light, the results presented by Hammani et al suggest that PNM1 might participate in the fine-tuning of this TCP-mediated coordinated expression.…”

TCP Transcription Factors Link the Regulation of Genes Encoding Mitochondrial Proteins with the Circadian Clock in Arabidopsis thaliana

“…TCP transcription factors bind cis-acting regulatory elements (CAREs), known as site II, with the core binding sequence TGGGC(C/T) in the promoter regions of various genes, the proliferating cell nuclear antigen from Arabidopsis and rice (Kosugi et al, 1995;Kosugi and Ohashi, 2002;Tré mousaygue et al, 2003), as well as cyclin B and ribosomal protein genes in Arabidopsis (Li et al, 2005). Site II elements have been shown to be involved in the regulation of nuclear-located genes encoding mitochondrial proteins, specifically cytochrome oxidase 6b-2 (Cyt6b-2), Cyt5b-2, cytochrome c1, and cytochrome c2 in Arabidopsis (Welchen and Gonzalez, 2005;Gonzalez et al, 2007;Comelli and Gonzalez, 2009;Mufarrege et al, 2009;Welchen et al, 2009). Site II elements have also been shown to be involved in the regulation of Alternative oxidase1c in Arabidopsis, a non-stress-inducible alternative oxidase gene in Arabidopsis (Ho et al, 2007).…”