14-3-3 Proteins Are Part of an Abscisic Acid-VIVIPAROUS1 (VP1) Response Complex in the Em Promoter and Interact with VP1 and EmBP1

Abstract

Protein-DNA complexes were formed when nuclear extracts from embryogenic rice suspension cultures or maize embryos were incubated with an abscisic acid-VIVIPAROUS1 (VP1) response element (Em1a) from the Em promoter. Monoclonal antibodies generated to GF14, a 14-3-3 protein from plants, resulted in gel retardation of the Em1a-protein complexes. Antibodies generated to the C and N termini of GF14 detected protein isoforms in rice nuclear and cytoplasmic extracts, but no differences in distribution of the GF14 isoforms were recognized between the nucleus and cytoplasm or when abscisic acid-treated and untreated tissues were compared. When recombinant GF14 fusion proteins from rice were added to nuclear extracts, novel complexes were formed that required the dimerization domain of GF14. Chemical cross-linking showed that GF-14 interacted with the basic leucine zipper factor EmBP1, which binds specifically to Em1a, and with VP1, which transactivates Em through Em1a. GF14 proteins from rice were shown to interact with VP1 in yeast through the dimerization domain of GF14. Our results indicated that GF14 interacts with both site-specific DNA binding proteins (i.e., EmBP1) and tissue-specific regulatory factors (i.e., VP1) and may provide a structural link between VP1 and the Em1a transcriptional complex.

Abscisic Acid Biosynthesis and Response

“…Additional interactions may involve other bZIP proteins, such as the ortholog of Table 4. Arabidopsis genes implicated in ABA response by reverse genetics EmBP1, that may be indirectly linked to ABI3 via interactions with a 14-3-3 protein, as described for connections among the maize proteins EmBP1, Vp1 and GF14 (Schultz et al, 1998). Such interactions may either promote or inhibit DNA binding (Nantel and Quatrano, 1996), and may trigger chromatin remodeling to permit ABA-mediated gene activation (Li et al, 1999).…”

Structural and functional properties of Viviparous1 genes in dormant wheat

“…Maize VP1 also activates the promoter of maize C1 gene that regulates anthocyanin synthesis, by directly binding to a Sph element on the promoter, and indirectly activates the transcription of the promoters of the genes encoding the late embryogenesis abundant proteins (LEAs) such as Em (McCarty et al, 1991;Hoecker et al, 1995). In addition to VP1, basic domain leucine-zipper (bZIP) transcription factors such as EmBP1 or ABI5 are needed for the activation of the Em promoter Schultz et al, 1998;Carles et al, 2002;Himmelbach et al, 2003). Meanwhile, VP1 is also known to downregulate the α-amylase expression in the aleurone cells of maize and barley (Shen et al, 2001;Hoecker et al, 1999).…”

Identification of 14-3-3-like protein in sugarcane (Saccharum officinarum)

“…the response to inhibition of photosynthesis in leaves). In plants, 14-3-3 proteins are also involved in the regulation of the plasma membrane H + -ATPase (Baunsgaard et al, 1998;Jahn et al, 1997), and have been found to bind to a number of proteins (including VP1 and EmBP1) which mediate abscisic acid-induced gene expression (Schultz et al, 1998). In addition, a bacterially expressed calcium-dependent protein kinase (Arabidopsis CPK-1) has been found to bind to, and be activated by, 14-3-3s (Camoni et al, 1998).…”