His-Asp phosphorelays are evolutionary-conserved powerful biological tactics for intracellular signal transduction. Such a phosphorelay is generally made up of "sensor histidine (His)-kinases", ..."response regulators", and "histidine-containing (HPt) phosphotransmitters". In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-Asp phosphorelays may be widely used for propagating environmental stimuli, such as phytohormones (e.g., ethylene and cytokinin). In this study, we first inspected extensively the occurrence of Arabidopsis response regulators in order to compile and characterize them. The results showed that this higher plant has, at least, 14 members of the family of response regulators that can be classified into two distinct subtypes (type-A and type-B), as judged from their structural designs, biochemical properties, and expression profiles. Comparative studies were conducted for each representative (ARR3 and ARR4 for type-A, and ARR10 for type-B). It was suggested that expression of the type-A response regulator is cytokinin-inducible, while that of the type-B response regulator appears to be not. Results from yeast two-hybrid analyses suggested that the type-B response regulator may have an ability to stably interact with a set of HPt phosphotransmitters (AHPs). These and other results will be discussed with special reference to the His-Asp phosphorelay signaling network in Arabidopsis thaliana.
His-Asp phosphorelays are evolutionary-conserved powerful biological tactics for intracellular signal transduction. Such a phosphorelay is generally made up of "sensor histidine (His)-kinases", ..."response regulators", and "histidine-containing (HPt) phosphotransmitters". In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-Asp phosphorelays may be widely used for propagating environmental stimuli, such as phytohormones (e.g., ethylene and cytokinin). In this study, we first inspected extensively the occurrence of Arabidopsis response regulators in order to compile and characterize them. The results showed that this higher plant has, at least, 14 members of the family of response regulators that can be classified into two distinct subtypes (type-A and type-B), as judged from their structural designs, biochemical properties, and expression profiles. Comparative studies were conducted for each representative (ARR3 and ARR4 for type-A, and ARR10 for type-B). It was suggested that expression of the type-A response regulator is cytokinin-inducible, while that of the type-B response regulator appears to be not. Results from yeast two-hybrid analyses suggested that the type-B response regulator may have an ability to stably interact with a set of HPt phosphotransmitters (AHPs). These and other results will be discussed with special reference to the His-Asp phosphorelay signaling network in Arabidopsis thaliana.
His to Asp phosphorelay signal transduction mechanisms involve three types of widespread signaling components: a sensor His-kinase, a response regulator, and a histidine-containing phosphotransfer ...(HPt) domain. In Arabidopsis, several sensor His-kinases have recently been discovered through extensive genetic studies. Furthermore, a recent search for response regulators in this higher plant revealed that it possesses a group of response regulators (ARK-series), each of which exhibits the phospho-accepting receiver function. However, no signal transducer containing the HPt domain has been reported. Here we identify three distinct Arabidopsis genes (AHP1 to AHP3), each encoding a signal transducer containing a HPt domain. Both in vivo and in vitro evidence that each AHP ban function as a phospho-transmitting HPt domain with an active histidine site was obtained by employing both the Escherichia coli and yeast His-Asp phosphorelay systems. It was demonstrated that AHP1 exhibits in vivo ability to complement a Mutational lesion of the yeast YPD1 gene, encoding a typical HPt domain involved in an osmosensing signal transduction. It was also demonstrated that AHPs fan interact in vitro with ARRs through tile His-Asp phosphotransfer reaction. It was thus suggested that the uncovered sensors-AHPs-ARRs lineups may play important roles in propagating environmental stimuli through the multistep His-Asp phosphorelay in Arabidopsis
In the higher plant, Arabidopsis thaliana, results from recent intensive studies suggested that His-to-Asp phosphorelay mechanisms are involved presumably in propagation of environmental stimuli, ...such as phytohormones (e.g. ethylene and cytokinin). Here we identified and characterized a set of novel Arabidopsis genes whose products considerably resemble the authentic response regulators (ARR-series) of Arabidopsis in the sense that they have a phospho-accepting receiver-like domain. However, they should be discriminated from the classical ones in the strict sense that they lack the invariant phospho-accepting aspartate site. They were thus named APRRs (Arabidopsis pseudo-response regulators). Two such representatives, APRR1 and APRR2, were characterized extensively through cloning of the corresponding cDNAs, in terms of their structural designs, biochemical properties, subcellular localization in plant cells, and expression profiles at the transcriptional level. The result of in vitro phosphorylation experiment with the Arabidopsis AHP phosphotransmitter suggested that the pseudo-receivers have no ability to undergo phosphorylation. The result of transient expression assay with onion epidermal cells showed that the GFPAPRR1 fusion protein has an ability to enter into the nuclei. The C-terminal domain of APRR1, termed CONSTANS-motif, appears to be responsible for the nuclearlocalization. The most intriguing result was that the accumulation of APRR1 transcript is subjected to a circadian rhythm. The APRR1 protein is identical to the one that was recently suggested to interact with the ABI3 (ABISCISIC ACID INSENSITIVE3) protein. These are discussed with special reference to the His-to-Asp phosphorelay signal transduction and circadian rhythm in Arabidopsis thaliana.
The His to Asp phosphotransfer signal transduction mechanism involves three common signaling domains: the transmitter (or His-kinase), the receiver, and the histidine-containing phototransfer (HPt) ...domain. Typically, a sensor kinase has a His-kinase domain and a response regulator has a receiver domain containing a phosphoaccepting aspartate, whereas a histidine-containing phototransfer domain serves as a mediator of the histidine-to-aspartate phosphotransfer. This signal transduction mechanism was thought to be restricted to prokaryotes. However, many examples have been discovered in diverse eukaryotic species including higher plants. In Arabidopsis, three sensor kinases have been characterized, namely, ETR1, ERS, and CKI1, which were suggested to be involved in ethylene- and cytokinin-dependent signal transduction pathways, respectively. To date, no response regulator has been discovered in higher plants. We identify five distinct Arabidopsis response regulator genes, each encoding a protein containing a receiver-like domain. In vivo and in vitro evidence that ARRs can function as phosphoaccepting response regulators was obtained by employing the Escherichia coli His-Asp phosphotransfer signaling system
Summary
Aim
To conduct a retrospective multicentre study at 31 medical centres in Japan, to investigate the association between the eradication of Helicobacter pylori and the development of new ...gastric cancer after endoscopic mucosal resection (EMR) for early gastric cancer.
Methods
Patients included those in whom early gastric cancer had been removed by EMR, and who had received follow‐up endoscopic treatment. All patients underwent follow‐up endoscopic treatment at least once a year after the initial EMR. The rate of new gastric cancer development was compared among those patients for whom H. pylori had been successfully eradicated and those with persistent H. pylori infection.
Results
The study included 2835 patients with a median follow‐up period of 2 years (range 0.5–12 years). Helicobacter pylori was eradicated in 356 patients (13%). Metachronous gastric cancers developed in eight (2%) patients among those who had been successfully treated for H. pylori, compared with 129 patients (5%) among those with persistent H. pylori infection (P = 0.021; OR = 0.42; 95% CI = 0.20–0.86).
Conclusion
Although longer term, prospective randomized controlled trials are needed to better estimate the extent and sustainability of possible benefits, this study suggests that the eradication of H. pylori may help reduce the incidence of metachronous gastric cancer.
To investigate the quantitative correlation between dynamics of ectomycorrhiza (ECM) formation and fruit-body production of the ammonia fungi, we treated forest soils in two ECM forests, a ...Castanopsis cuspidata forest and a Quercus serrata forest, in warm temperate Japan with urea to induce fruiting of ammonia fungi. We identified the ectomycorrhizae of two known species of ammonia fungi, Alnicola lactariolens and Hebeloma vinosophyllum, using morphological typing and PCR-RFLP. ECM initiation, increase, and subsequent decrease preceded the start, increase, and decrease of fruit-body production for each species. We also found many kinds of ECM fungi that did not develop fruit bodies after urea treatment during the observation period, which suggests that it is necessary to expand the definition of ammonia fungi from one that refers solely to the species reproducing on the ground to one which includes those in somatic forms in the soil.
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