The AP2 domain of APETALA2 defines a large new family of DNA binding proteins in  Arabidopsis

Abstract

APETALA2 (AP2) plays an important role in the control of Arabidopsis f lower and seed development and encodes a putative transcription factor that is distinguished by a novel DNA binding motif referred to as the AP2 domain. In this study we show that the AP2 domain containing or RAP2 (related to AP2) family of proteins is encoded by a minimum of 12 genes in Arabidopsis. The RAP2 genes encode two classes of proteins, AP2-like and EREBP-like, that are defined by the number of AP2 domains in each polypeptide as well as by two sequence motifs referred to as the YRG and RAYD elements that are located within each AP2 domain. RAP2 genes are differentially expressed in f lower, leaf, inf lorescence stem, and root. Moreover, the expression of at least three RAP2 genes in vegetative tissues are controlled by AP2. Thus, unlike other f loral homeotic genes, AP2 is active during both reproductive and vegetative development.Genetic and molecular studies have defined an evolutionarily conserved network of genes that control flower development in Arabidopsis and in other plant species (1, 2). In Arabidopsis, the homeotic gene APETALA2 (AP2) has been shown to control three important processes during flower development: (i) the establishment of flower meristem identity (3, 4), (ii) the specification of flower organ identity and the regulation of floral organogenesis (5-9), and (iii) the temporal and spatial regulation of flower homeotic gene activity (10). Genetic studies have shown that AP2 is also required for normal ovule and seed development (9,11,12). Consistent with its genetic functions AP2 is expressed throughout flower development, in immature floral buds, in all four types of flower organ primordia, and in developing ovules and seeds (ref. 9; B. den Boer and K.D.J., unpublished data). Unlike most other flower homeotic genes, AP2 is also expressed at the mRNA level in both stem and leaf, suggesting that AP2 may also function during vegetative development (9). However, ap2 mutant plants show no dramatic defects during either stem or leaf development. One hypothesis to explain this apparent paradox is that the Arabidopsis genome may be genetically redundant for AP2 function during stem and leaf development.Previous studies have suggested that AP2 functions as a nuclear transcription factor in plant cells (9). DNA sequence analysis showed that AP2 encodes a theoretical polypeptide of 432 amino acids that is distinct from known fungal and animal regulatory proteins (9). One important feature of the AP2 protein is a novel 68-amino acid repeated motif called the AP2 domain. The AP2 domain has been shown to be essential for AP2 functions and contains an 18-amino acid core region that is predicted to form an amphipathic ␣-helix (9). In tobacco, four AP2-like AP2 domain containing proteins have been identified (13). These proteins, referred to as the ethylene responsive element binding proteins (EREBPs), are thought to regulate gene expression at the transcriptional level. In vitro studies have shown that the EREBP AP2 do...

Overexpression of the Tobacco Tsi1 Gene Encoding an EREBP/AP2-Type Transcription Factor Enhances Resistance against Pathogen Attack and Osmotic Stress in Tobacco

“…The EREBP/AP2 motif contains an 18-amino acid core region that has been proposed to form an amphipathic ␣-helix; such a secondary structure has been implicated in proteinprotein interactions to facilitate DNA binding (Okamuro et al, 1997). However, the present binding studies cannot determine whether Tsi1 binds to the GCC box or the DRE/CRT box as a monomer or some form of multimer.…”

“…Also, many experiments have shown that certain types of transcription factors required cofactor(s) or post-translational modification for their activation potential and DNA binding properties in plants (Despres et al, 2000; Gu et al, 2000). It is thus possible that Tsi1 may require post-translational modification or a putative cofactor for its function in response to osmotic stress.The EREBP/AP2 motif contains an 18-amino acid core region that has been proposed to form an amphipathic ␣-helix; such a secondary structure has been implicated in proteinprotein interactions to facilitate DNA binding (Okamuro et al, 1997). However, the present binding studies cannot determine whether Tsi1 binds to the GCC box or the DRE/CRT box as a monomer or some form of multimer.…”

Identification and mapping of SNPs from ESTs in sunflower

“…For instance, an APETALA2 (AP2)-like protein (HT160) maps coincident with QTLs controlling flowering time and achene size ( Table 2). AP2 is a floral homeotic gene, and AP2 and AP2-like proteins play important roles in the control of flower and seed development (Okamuro et al 1997;Maes et al 2001;Aukerman and Sakai 2003;Faris et al 2003). Likewise, a putative cell division control protein (HT189) colocalizes with QTLs affecting relative growth rate, leaf area, stem diameter, and height, whereas the bZIP transcription factors HT087 and HT179 are associated with stem and leaf size, and achene and disk size QTLs, respectively (Table 2).…”

Heterologous expression of the BABY BOOM AP2/ERF transcription factor enhances the regeneration capacity of tobacco (Nicotiana tabacum L.)

“…The Arabidopsis AP2/ERF family comprises a large class of 144 transcription factors with diverse roles throughout the plant life cycle. The members of this class of regulatory proteins all contain the conserved AP2/ERF domain, a 60-70 amino acid region that is thought to mediate DNA binding and protein-protein interactions (Jofuku et al 1994;Okamura et al 1997). The AP2/ERF family has been organized into Wve phylogenetically distinct subfamilies that diVer in the number of AP2/ERF domains, as well as the amino acid similarity between these domains (Sakuma et al 2002).…”