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Main conclusion: NO was involved in H2-induced adventitious rooting by regulating the protein and gene expressions of PM H+-ATPase and 14-3-3. Simultaneously, the interaction of PM H+-ATPase and 14-3-3 protein was also involved in this process. Hydrogen gas (H2) and nitric oxide (NO) have been shown to be involved in plant growth and development. The results in this study revealed that NO was involved in H2-induced adventitious root formation. Western blot (WB) analysis showed that the protein abundances of plasma membrane H+-ATPase (PM H+-ATPase) and 14-3-3 protein were increased after H2, NO, H2 plus NO treatments, whereas their protein abundances were down regulated when NO scavenger carboxy‐2‐(4‐carboxyphenyl)‐4,4,5,5‐tetramethylimidazoline‐1‐oxyl‐3‐oxide (cPTI O) was added. Moreover, the mRNA abundances of the HA3 and 14-3-3(7) gene as well as the activities of PM H+-ATPase (EC 3.6.1.35) and H+ pump were in full agreement with the changes of protein abundance. Phosphorylation of PM H+-ATPase and the interaction of PM H+-ATPase and 14-3-3 protein were detected by co-immunoprecipitation analysis. H2 and NO significantly up regulated the phosphorylation of PM H+-ATPase and the interaction of PM H+-ATPase and 14-3-3 protein. Conversely, the stimulation of PM H+-ATPase phosphorylation and protein interaction were significantly diminished by cPTIO. Protein interaction activator fusicoccin (FC) and inhibitor adenosine monophosphate (AMP) of PM H+-ATPase and 14-3-3 were used in this study, and the results showed that FC significantly increased the abundances of PM H+-ATPase and 14-3-3, while AMP showed opposite trends. We further proved the critical roles of PM H+-ATPase and 14-3-3 protein interaction in NO–H2-induced adventitious root formation. Taken together, our results suggested that NO might be involved in H2-induced adventitious rooting by regulating the expression and the interaction of PM H+-ATPase and 14-3-3 protein. [ABSTRACT FROM AUTHOR]

Leucine-rich repeat (LRR)-containing transmembrane receptor-like kinases (RLKs) are important components of plant signal transduction. TheArabidopsis thalianasomatic embryogenesis receptor-like kinase 1 (AtSERK1) is an LRR-RLK proposed to participate in a signal transduction cascade involved in embryo development. By yeast two-hybrid screening we identifiedAtCDC48, a homologue of the mammalian AAA-ATPase p97 and GF14?, a member of theArabidopsisfamily of 14-3-3 proteins asAtSERK1 interactors. In vitro, theAtSERK1 kinase domain is able to transphosphorylate and bind bothAtCDC48 and GF14?. In yeast,AtCDC48 interacts with GF14? and with the PP2C phosphatase KAPP. In plant protoplastsAtSERK1 interacts with GF14?. [ABSTRACT FROM AUTHOR]

An antisense nitrite reductase (NiR, EC 1.7.7.1) tobacco (Nicotiana tabacum L.) transformant (clone 271) was used to gain insight into a possible correlation between nitrate reductase (NR, EC 1.6.6.1)-dependent nitrite accumulation and nitric oxide (NO·) production, and to assess the regulation of signal transduction in response to stress conditions. Nitrite concentrations of clone 271 leaves were 10-fold, and NO· emission rates were 100-fold higher than in wild type leaves. Increased protein tyrosine nitration in clone 271 suggests that high NO· production resulted in increased peroxynitrite (ONOO–) formation. Tyrosine nitration was also observed in vitro by adding peroxynitrite to leaf extracts. As in mammalian cells, NO· and derivatives also increased synthesis of proteins like 14-3-3 and cyclophilins, which are both involved in regulation of activity and stability of enzymes. [ABSTRACT FROM AUTHOR]

A 14-3-3 protein has been cloned and sequenced from a cDNA library constructed from mRNAs of mature pollen grains of Lilium longiflorum Thunb. Monoclonal antibodies (MUP 5 or MUP 15) highly specific against 14-3-3 proteins recognised a 30-kDa protein in the cytoplasmic fraction of many various lily tissues (leaves, bulbs, stems, anther filaments, pollen grains, stigmas) and in other plants (Arabidopsis seedlings, barley recombinant 14-3-3). In addition, 14-3-3 proteins were detected in a microsomal fraction isolated from pollen grains and tubes, and the amount of membrane-bound 14-3-3 proteins as well as the amount of the plasma membrane (PM) H+ ATPase increased during germination of pollen grains and tube growth. No change was observed in the cytoplasmic fraction. A further increase in the amount of 14-3-3 proteins in the microsomal fraction was observed when pollen grains were incubated in germination medium containing 1 μM fusicoccin (FC) whereas the number of 14-3-3s in the cytoplasmic fraction decreased. Fusicoccin also protected membrane-bound 14-3-3 proteins from dissociation after washing with the chaotropic salt KI. Furthermore, FC stimulated the PM H+ ATPase activity, the germination frequency and the growth rate of pollen tubes, thus indicating that a modulation of the PM H+ ATPase activity by interaction with 14-3-3 proteins may regulate germination and tube growth of lily pollen. [ABSTRACT FROM AUTHOR]

The nitrate reductase activity from Chlamydomonas reinhardtii was not altered when extracts were incubated with yeast 14-3-3 proteins in the presence of Mg-ATP. However, the C. reinhardtii extracts contained 14-3-3 proteins capable of inhibiting the spinach nitrate reductase, raising the question of their physiological substrates. Two C. reinhardtii proteins of about 48 and 35 kDa were eluted from 14-3-3 affinity chromatography columns and bound to 14-3-3s in overlay assays. The 48-kDa protein corresponded to the cytosolic isoform of glutamine synthetase (GS1). The GS1 was phosphorylated by a Ca2+- and calmodulin-dependent protein kinase partially purified from the alga. However, neither phosphorylation nor 14-3-3 binding seemed to change GS catalytic activity. [ABSTRACT FROM AUTHOR]

About thirty years after the initial identification of 14-3-3 proteins in mammalian brain, they are now thought to be ubiquitous among eukaryotes. We identified five cDNAs encoding 14-3-3 proteins of Nicotiana tabacum L. using a polymerase chain reaction (PCR)-based screening strategy. A phylogenetic analysis was carried out with 14-3-3 amino-acid sequences from twelve plant species. The results showed that 14-3-3 proteins of plants can be divided into at least five different subgroups. Four of these subgroups resulted from early gene duplication events that happened prior to the speciation of most of the plant species considered. Interestingly, 14-3-3 epsilon isoforms from mammals and insects form one subgroup together with epsilon-like isoforms from plants. The 14-3-3 genes known from monocots descend from the same ancestor, forming the fifth subgroup. [ABSTRACT FROM AUTHOR]

Taking the binding of fusicoccin to plasma membranes as an indicator of complex formation between the 14-3-3 dimer and H+-ATPase, we assessed the effect of osmotic stress on the interaction of these proteins in suspension-cultured cells of sugar beet (Beta vulgaris L.). An increase in osmolarity of the cell incubation medium, accompanied by a decrease in turgor, was found to activate the H+ efflux 5-fold. The same increment was observed in the number of high-affinity fusicoccin-binding sites in isolated plasma membranes; the 14-3-3 content in the membranes increased 2- to 3-fold, while the H+-ATPase activity changed only slightly. The data obtained indicate that osmotic regulation of H+-ATPase in the plant plasma membrane is achieved via modulation of the coupling between H+ transport and ATP hydrolysis, and that such regulation involves 14-3-3 proteins. [ABSTRACT FROM AUTHOR]