The CCAAT binding factor can mediate interactions between CONSTANS‐like proteins and DNA

Abstract

SummaryCONSTANS-Like (COL) proteins are plant-specific nuclear regulators of gene expression but do not contain a known DNA-binding motif. We tested whether a common DNA-binding protein can deliver these proteins to specific cis-acting elements. We screened for proteins that interact with two members of a subgroup of COL proteins. These COL proteins were Tomato COL1 (TCOL1), which does not seem to be involved in the control of flowering time, and the Arabidopsis thaliana CONSTANS (AtCO) protein which mediates photoperiodic induction of flowering. We show that the C-terminal plant-specific CCT (CO, CO-like, TIMING OF CAB EXPRESSION 1) domain of both proteins binds the trimeric CCAAT binding factor (CBF) via its HAP5/NF-YC component. Chromatin immunoprecipitation demonstrated that TCOL is recruited to the CCAAT motifs of the yeast CYC1 and HEM1 promoters by HAP5. In Arabidopsis, each of the three CBF components is encoded by several different genes that are highly transcribed. Under warm long days, high levels of expression of a tomato HAP5 (THAP5a) gene can reduce the flowering time of Arabidopsis. A mutation in the CCT domain of TCOL1 disrupts the interaction with THAP5 and the analogous mutation in AtCO impairs its function and delays flowering. CBFs are therefore likely to recruit COL proteins to their DNA target motifs in planta.

The Evolutionary History of CBF Transcription Factors: Gene Duplication of CCAAT – Binding Factors NF-Y in Plants

“…These observations indicate that plant NF-Y subunits might act as general transcription factors, as in mammals (Yamamoto et al, 2009). Although a complete functional plant NF-Y complex has not yet been described, the individual subunits are known to be involved in a number of important physiological processes, such as specific developmental processes and response to environmental stimuli (Lotan et al, 1998;Kusnetsov et al, 1999;Miyoshi et al, 2003;Ben-Naim et al, 2006;Combier et al, 2006;Wenkel et al, 2006;Cai et al, 2007;Nelson et al, 2007;Warpeha et al, 2007;Siefers et al, 2009). A well-established example is the NF-YB subunit gene called LEAFY COTYLEDON-1 (LEC1), which specifically controls embryo development, especially the maturation phase.…”

“…Another study showed that overexpression of maize NF-YA5 reduced drought susceptibility, anthocyanin production and stomatal aperture, while nf-ya5 mutants had the expected opposite phenotype in each situation (Li et al, 2008). In addition, several publications strongly suggest that NF-Y transcription factors are also involved in photoperiod-regulated flowering (Ben-Naim et al, 2006;Wenkel et al, 2006;Siefers et al, 2009). We adopted a high throughput comparative genomic approach to conduct a broad survey of fully sequenced genomes, including representatives of amoebozoa, yeasts, fungi, algae, mosses, plants, vertebrate and invertebrate species to identify the presence of homologous genes coding for each of the three subunits that form the NF-Y transcription factor (Table 1).…”

“…Besides, at least some plant NF-YA and NF-YB subunits have been shown to complement yeast mutant strains lacking the corresponding NF-Y subunit. Additionally, several groups have demonstrated that each of the three plant NF-Y proteins can substitute their yeast counterparts in gene expression assays (Edwards et al, 1998;Masiero et al, 2002;Ben-Naim et al, 2006;Siefers et al, 2009). These observations indicate that plant NF-Y subunits might act as general transcription factors, as in mammals (Yamamoto et al, 2009).…”

Transcriptional regulation of an Arabidopsis gene encoding a CCT domain-containing protein during endoplasmic reticulum stress

“…Recent studies suggested that CCT domain-containing proteins function in cooperation with the NF-Y complex. For instance, a tomato homolog of CO, one of the founding members of the CCT protein family, interacts with a tomato HAP5/NF-YC protein (Ben-Naim et al 2006). Another report also suggested that Arabidopsis CO and related protein COL15 interact with HAP5/NF-YC and regulate flowering time (Wenkel et al 2006).…”

Involvement of the N-terminal B-box Domain of Arabidopsis BBX32 Protein in Interaction with Soybean BBX62 Protein

“…B-box domain-containing proteins have been identified in both di-and mono-cotyledenous plants (2, 4 -6). It has been proposed that the B-box domain is involved in the mediation of protein-protein interactions, including both heterodimerization of B-box family members and interactions with described DNA-binding proteins (4,5). Plant B-box proteins play a role in light-regulated transcription and development through their interactions with key regulators of the light-signaling pathway (5,7,8).…”