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Response regulators implicated in His-to-Asp phosphotransfer signaling in Arabidopsis.

ABSTRACT: 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.

SUBMITTER: Imamura A

PROVIDER: S-EPMC19464 | biostudies-literature | 1998 Mar

REPOSITORIES: biostudies-literature

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Response regulators implicated in His-to-Asp phosphotransfer signaling in Arabidopsis.

Imamura A A Hanaki N N Umeda H H Nakamura A A Suzuki T T Ueguchi C C Mizuno T T

Proceedings of the National Academy of Sciences of the United States of America 19980301 5

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 ...[more]

PMID: 9482949

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Project description:BackgroundAuxins play key roles in the phytohormone network. Early auxin response genes in the AUX/IAA, SAUR, and GH3 families show functional redundancy, which makes it very difficult to study the functions of individual genes based on gene knockout analysis or transgenic technology. As an alternative, chemical genetics provides a powerful approach that can be used to address questions relating to plant hormones.ResultsBy screening a small-molecule chemical library of compounds that can induce abnormal seedling and vein development, we identified and characterized a piperazine compound 1-[(4-bromophenoxy) acetyl]-4-[(4-fluorophenyl) sulfonyl] piperazine (ASP). The Arabidopsis DR5::GFP line was used to assess if the effects mentioned were correlated with the auxin response, and we accordingly verified that ASP altered the auxin-related pathway. Subsequently, we examined the regulatory roles of ASP in hypocotyl and root development, auxin distribution, and changes in gene expression. Following ASP treatment, we detected hypocotyl elongation concomitant with enhanced cell elongation. Furthermore, seedlings showed retarded primary root growth, reduced gravitropism and increased root hair development. These phenotypes were associated with an increased induction of DR5::GUS expression in the root/stem transition zone and root tips. Auxin-related mutants including tir1-1, aux1-7 and axr2-1 showed phenotypes with different root-development pattern from that of the wild type (Col-0), and were insensitive to ASP. Confocal images of propidium iodide (PI)-stained root tip cells showed no detectable damage by ASP. Furthermore, RT-qPCR analyses of two other genes, namely, Ethylene Response Factor (ERF115) and Mediator 18 (MED18), which are related to cell regeneration and damage, indicated that the ASP inhibitory effect on root growth was not attributable to toxicity. RT-qPCR analysis provided further evidence that ASP induced the expression of early auxin-response-related genes.ConclusionsASP altered the auxin response pathway and regulated Arabidopsis growth and development. These results provide a basis for dissecting specific molecular components involved in auxin-regulated developmental processes and offer new opportunities to discover novel molecular players involved in the auxin response.

Project description:In plants, the multistep phosphorelay signaling pathway mediates responses to environmental factors and plant hormones. This system is composed of three successive partners: hybrid Histidine-aspartate Kinases (HKs), Histidine-containing Phosphotransfer proteins (HPts), and Response Regulators (RRs). Among the third partners, B-type RR family members are the final output elements of the pathway; they act as transcription factors and clearly play a pivotal role in the early response to cytokinin in Arabidopsis. While interactions studies between partners belonging to the multistep phosphorelay system are mainly focused on protagonists involved in cytokinin or ethylene pathways, very few reports are available concerning partners of osmotic stress signaling pathway.In Populus, we identified eight B-type RR proteins, RR12-16, 19, 21 and 22 in the Dorskamp genotype. To assess HPt/B-type RR interactions and consequently determine potential third partners in the osmosensing multistep phosphorelay system, we performed global yeast two-hybrid (Y2H) assays in combination with Bimolecular Fluorescence Complementation (BiFC) assays in plant cells. We found that all B-type RRs are able to interact with HPt predominant partners (HPt2, 7 and 9) of HK1, which is putatively involved in the osmosensing pathway. However, different profiles of interaction are observed depending on the studied HPt. HPt/RR interactions displayed a nuclear localization, while the nuclear and cytosolic localization of HPt and nuclear localization of RR proteins were validated. Although the nuclear localization of HPt/RR interaction was expected, this work constitutes the first evidence of such an interaction in plants. Furthermore, the pertinence of this partnership is reinforced by highlighting a co-expression of B-type RR transcripts and the other partners (HK1 and HPts) belonging to a potential osmosensing pathway.Based on the interaction studies between identified B-type RR and HPt proteins, and the co-expression analysis of transcripts of these potential partners in poplar organs, our results favor the model that RR12, 13, 14, 16 and 19 are able to interact with the main partners of HK1, HPt2, 7 and 9, and this HPt/RR interaction occurs within the nucleus. On the whole, the five B-type RRs of interest could be third protagonists putatively involved in the osmosensing signaling pathway in Populus.

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Response regulators implicated in His-to-Asp phosphotransfer signaling in Arabidopsis.

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Response regulators implicated in His-to-Asp phosphotransfer signaling in Arabidopsis.

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