In this review we highlight the advances achieved in the investigation of the role of 14-3-3 proteins in hormone signaling, biosynthesis, and transport. 14-3-3 proteins are a family of conserved molecules that target a number of protein clients through their ability to recognize well-defined phosphorylated motifs. As a result, they regulate several cellular processes, ranging from metabolism to transport, growth, development, and stress response. High-throughput proteomic data and two-hybrid screen demonstrate that 14-3-3 proteins physically interact with many protein clients involved in the biosynthesis or signaling pathways of the main plant hormones, while increasing functional evidence indicates that 14-3-3-target interactions play pivotal regulatory roles. These advances provide a framework of our understanding of plant hormone action, suggesting that 14-3-3 proteins act as hubs of a cellular web encompassing different signaling pathways, transducing and integrating diverse hormone signals in the regulation of physiological processes.
Plants and protozoa contain a unique family of calcium-dependent protein kinases (CDPKs) which are defined by the presence of a carboxyl-terminal calmodulin-like regulatory domain. We present biochemical evidence indicating that at least one member of this kinase family can be stimulated by 14-3-3 proteins. Isoform CPK-1 from the model plant Arabidopsis thaliana was expressed as a fusion protein in E. coli and purified. The calcium-dependent activity of this recombinant CPK-1 was shown to be stimulated almost twofold by three different 14-3-3 isoforms with 50% activation around 200 nM. 14-3-3 proteins bound to the purified CPK-1, as shown by binding assays in which either the 14-3-3 or CPK-1 were immobilized on a matrix. Both the 14-3-3 binding and activation of CPK-1 were specifically disrupted by a known 14-3-3 binding peptide LSQRQRSTpSTPNVHMV (IC SH = 30 W WM). These results raise the question of whether 14-3-3 can modulate the activity of CDPK signal transduction pathways in plants.z 1998 Federation of European Biochemical Societies.
The H؉ -ATPase is a key enzyme for the establishment and maintenance of plasma membrane potential and energization of secondary active transport in the plant cell. The phytotoxin fusicoccin induces H ؉ -ATPase activation by promoting the association of 14-3-3 proteins. It is still unclear whether 14-3-3 proteins can represent natural regulators of the proton pump, and factors regulating 14-3-3 binding to the H ؉ -ATPase under physiological conditions are unknown as well. In the present study in vivo and in vitro evidence is provided that 14-3-3 proteins can associate with the H ؉ -ATPase from maize roots also in a fusicoccin-independent manner and that the interaction depends on the phosphorylation status of the proton pump. Furthermore, results indicate that phosphorylation of H ؉ -ATPase influences also the fusicoccin-dependent interaction of 14-3-3 proteins. Finally, a protein phosphatase 2A able to impair the interaction between H ؉
The structure of the fuscopeptins, bioactive lipodepsipeptides produced in culture by the gramineae pathogen Pseudomonas fuscovaginae, has been determined. The combined use of FAB mass spectrometry, NMR spectroscopy and chemical and enzymatic procedures allowed one to define a peptide moiety corresponding to ZDhb-DPro-LLeu-DAIa-DAIa-DAla-DAIaDVai-Gly-DAIa-DVaI-DAIa-DVaI-ZDhb-DaThr-LAIa-LDabDDab-LPbe with the terminal carboxyl group closing a macrocyclic ring on the hydroxyl group of the allothreonine residue. The N-terminus is in turn acylated by 3-hydroxyoctanoate in fuscopeptin A and 3-hydroxydecanoate in fuscopeptin B. Some preliminary data on the biological activity of fuscopeptins are also reported.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.